Whiptail lizard guilds consisting of different combinations of parthenogenetic Aspidoscelis exsanguis, Aspidoscelis neomexicana, and Aspidoscelis tesselata pattern classes C and D and gonochoristic Aspidoscelis sexlineata viridis inhabit numerous sites in the immediate vicinity of Conchas Lake, San Miguel County, New Mexico. Based on morphological identification by other workers of specimens collected in 1978, A. neomexicana was the species most recently added to the list of whiptail lizards known to occur at Conchas Lake, about 190 km east of its main distribution area in the Rio Grande Valley. We sampled guilds consisting of A. neomexicana and its congeners at Conchas Lake from 2000 through 2003. In 2002 we also collected specimens of what appeared to be another tokogenetic array of A. neomexicana east of the Rio Grande Valley in syntopy with A. tesselata E and A. sexlineata viridis at Fort Sumner, De Baca County, New Mexico. Comparison of karyotypes revealed that individuals of A. tesselata and those assigned by their discoverers to A. neomexicana from Conchas Lake and Fort Sumner have identical diploid karyotypes (2n = 46) that include diagnostic haploid complements of chromosomes derived from independent hybridizations between species in the tigris and sexlineata species groups. Consequently, we used electrophoretic data for 23 gene loci, of which the sMDH, sMDHP, sIDH, ESTD, PEPA, PEPB, ADA, MPI, GPI, and PGM2 loci were definitive, to further validate the hypothesis that the disjunct groups of putative A. neomexicana in eastern New Mexico had been correctly identified. The specimens analyzed electrophoretically also indicated that the Conchas Lake clone of A. neomexicana is identical to the most widely distributed clone of the species in the Rio Grande Valley of New Mexico and that the Fort Sumner clone possessed a distinctive allele.
We describe the habitat for A. neomexicana at Conchas Lake at three sites north of the Canadian River and two sites south of the river. Two of the sites north of the Canadian River were studied as examples of guilds that did not include A. sexlineata viridis. The latter species was observed with A. neomexicana, A. tesselata, and A. exsanguis at one site north of the Canadian River and two sites south of the river. At Fort Sumner, we studied A. neomexicana at two sites where it was syntopic with A. tesselata E and A. sexlineata viridis.
We identified 15 lizards from three sites at Conchas Lake as hybrids of A. neomexicana × A. sexlineata viridis. Most of these hybrids were found in either patchy or weedy chronically disturbed habitats in which the parental forms were forced into unusually close syntopic relationships. Hybrids between these parental forms were collected in each year from 2000– 2003 and represented a minimum of four and a maximum of five generations.
Although hybrids of A. neomexicana × A. sexlineata viridis were characterized by distinctive color patterns, all w
INTRODUCTION
Complex geographic and physiographic features similar to those exploited in the impoundment of Conchas Lake have also formed terrestrial habitats that support diverse communities of diurnal ground-dwelling lizards (Teiidae: Aspidoscelis Fitzinger, 1843) in San Miguel County, New Mexico. A combination of three cloned hybrid all-female species (Aspidoscelis exsanguis, Aspidoscelis neomexicana, and Aspidoscelis tesselata pattern classes C and D) and one gonochoristic species (Aspidoscelis sexlineata viridis) occur in the variety of habitats in the immediate vicinity of Conchas Lake. The most recently discovered of these populations, identified as Cnemidophorus neomexicanus (= A. neomexicana) on the basis of morphology by Leuck et al. (1981), was separated by a hiatus of about 190 km from the nearest record known at that time for the species in the Rio Grande Valley at San Pedro, Sandoval County, New Mexico. Based on zoogeographic considerations and fieldwork conducted at Conchas Lake by students of whiptail lizards such as J.W. Wright (Wright and Lowe, 1967, 1968; Wright, 1971; Tanner, 1975; Densmore et al., 1989), E.D. Parker, Jr. (Parker and Selander, 1984), and CJC (Cole et al., 1988) that did not reveal the presence of A. neomexicana there prior to 1978, Cole et al. (1988), Degenhardt et al. (1996), and Persons and Wright (1999) agreed with the stated opinion of Leuck et al. (1981) that its occurrence in San Miguel County probably resulted from introduction by humans. Recently, disjunct populations identified as A. neomexicana have also been reported in Petrified Forest National Park in the Rio Puerco Valley, Apache County, Arizona, by Persons and Wright (1999) and in Fort Sumner in the Pecos River Valley, De Baca County, New Mexico, by Taylor (2002). Not unlike the discovery of this species at Conchas Lake, confirmation of its presence in Fort Sumner by Taylor (2002) was preceded by the field studies of other investigators including E.D. Parker, Jr. (Parker and Selander, 1984) and JMW (Taylor et al., 1997), who found only A. sexlineata viridis and A. tesselata in the city. At present, A. neomexicana (mostly limited to the Rio Grande Valley except for a few disjunct groups) is known to be syntopic with A. sexlineata viridis (limited in New Mexico to the eastern part of the state) only at Conchas Lake (Walker et al., 1990, 1992) and Fort Sumner (this study).
Aspidoscelis neomexicana is an obligate parthenogenetic species of cloned descent from one or a few hybrids of A. tigris marmorata ♀ × A. inornata ♂ (Lowe and Wright, 1966a, 1966b; Neaves, 1969; Cuellar, 1977; Brown and Wright, 1979; Parker and Selander, 1984; Cole et al., 1988; Densmore et al., 1989). Nevertheless, at several sites along the Rio Grande in New Mexico, an unusual interruption in parthenogenetic reproduction occurs when occasional insemination of females of A. neomexicana by males of its paternal progenitor A. inornata produces hybrids (Axtell, 1966; Taylor and Medica, 1966; Wright and Lowe, 1967; Christiansen and Ladman, 1968; Christiansen et al., 1971; Cuellar and McKinney, 1976; Taylor and Walker, 1996). Also, hybrids of A. neomexicana × A. tigris have been reported from Hidalgo and Grant counties, New Mexico (Dessauer et al., 2000). The apparently sterile hybrids of A. neomexicana × A. inornata reported to date have included both allotriploid females and males; the two reported hybrids of A. neomexicana × A. tigris were sterile allotriploid females. Walker et al. (1990) also described one hybrid male and mentioned a putative hybrid female of A. neomexicana × A. sexlineata viridis from Conchas Lake. That report stimulated GJM to undertake an intensive field study in 2000–2003 to understand ecological and morphological aspects of hybridization between these species. Subsequently, the study was expanded to a collaboration among the present authors to include cytological and molecular aspects of hybridization between A. neomexicana and A. sexlineata viridis.
We have determined that the species composition and local distribution of Aspidoscelis guilds at Conchas Lake reflect site- specific ecological characteristics largely resulting from human activities. During the study, the most widely distributed species at Conchas Lake were A. neomexicana and A. tesselata C, whereas the forms with more restricted local distributions were A. sexlineata viridis, A. exsanguis, and A. tesselata D. In our 2002–2003 investigation of the recently discovered populations of A. neomexicana in Fort Sumner (Taylor, 2002), the species was observed in syntopy with both A. tesselata E and A. sexlineata viridis at each site. At Conchas Lake and Fort Sumner, we observed that some individuals of each of the all-female species of Aspidoscelis present came into contact with males of A. sexlineata viridis during their normal activities. However, offspring resulting from occasional inseminations of normally parthenogenetic females of A. neomexicana by males of A. sexlineata viridis were the only products of hybridization that we found in the two areas.
Maslin et al. (1958), Wright and Lowe (1967), Taylor and Walker (1996), and Walker (1997) have contributed to the controversy involving the genealogy of the lectotype of Cnemidophorus perplexus Baird and Girard, 1853, for which no genetic data exist. Based on morphology, Wright and Lowe (1967) concluded that this type specimen is a hybrid female of C. neomexicanus × C. inornatus (= A. neomexicana × A. inornata), whereas Maslin et al. (1958), Taylor and Walker (1996), and Walker (1997) inferred that this type is merely an unusually large individual of C. neomexicanus (= A. neomexicana). This case convincingly shows that opinions can vary on whether certain female specimens resembling A. neomexicana in color pattern and scutellation are unusual individuals of this species or hybrids between it and a gonochoristic species.
Ideally, then, all of the putative hybrids of A. neomexicana × A. sexlineata viridis reported herein would have been accompanied by genetic data verifying their parentage. Unfortunately, because of their extreme wariness, only 1 of 13 putative hybrids from the vicinity of the South Recreation Area at Conchas Lake could be obtained alive for subsequent karyotypic and electrophoretic analyses. Nevertheless, we join Walker et al. (1989, 1990, 1994, 2000), and Taylor et al. (2001) in the opinion that it becomes possible to use subtle morphological characters to identify hybrids between an all-female and gonochoristic species of Aspidoscelis lacking genetic data, particularly when compared with additional specimens having genetic data.
This collaboration focused on obtaining ecological (GJM and JMW), morphological (GJM and JMW), karyotypic (CJC), and electrophoretic (CJC and HCD) data forming the biological context within which to answer the following questions: (1) Are the specimens from Conchas Lake and Fort Sumner that appeared to be A. neomexicana really this species or are they something else, such as a variant of A. tesselata or a new species? (2) Are the specimens from Conchas Lake and Fort Sumner that appear to be A. neomexicana representatives of the same clone? (3) Are the apparent hybrids of A. neomexicana × A. sexlineata viridis (N = 15) from Conchas Lake really that, that is, triploids with genomes from three ancestral gonochoristic taxa (A. neomexicana [= A. tigris marmorata × A. inornata] × A. sexlineata viridis)? (4) How do the protein genotypes for a hybrid compare with its parental species? (5) Is the presence of the hybrid genome accompanied by a unique combination of features of color pattern compared to variation in the parental species? (6) What patterns of univariate and multivariate morphological variation can be discerned in hybrids of A. neomexicana × A. sexlineata viridis in comparison to their parental species? (7) What are the reproductive consequences of the hybrid genome? (8) What ecological conditions facilitate hybridization between A. neomexicana and A. sexlineata viridis at Conchas Lake?
MATERIALS AND METHODS
Taxonomic Treatment and Pattern Class Designations
We followed Reeder et al. (2002) in using the recently resurrected generic name Aspidoscelis for the North and Central American parthenogenetic and gonochoristic species of whiptail lizards in the cozumela, deppei, sexlineata, tesselata, and tigris species groups recently partitioned from Cnemidophorus to partially resolve paraphyly in that genus. Spellings of the names neomexicana, sexlineata, and tesselata reflect the femine gender of Aspidoscelis (Reeder et al., 2002). We reference the two color pattern variants of A. tesselata at Conchas Lake as C (sensu Zweifel, 1965) and D (sensu Zweifel, 1965; Taylor et al., 1996) as a compromise position preferred by GJM and JMW pending further study (Manning and Walker, unpubl.) of the statistically based C-E redesignation of C by Taylor et al. (2003).
Study Sites at Conchas Lake and Fort Sumner
Conchas Lake is an Army Corps of Engineers impoundment. Land joining the north shore of the Conchas River arm and the west shore of the Canadian River arm of the lake are parts of private ranches, as are parts of the south and east shores. Conchas Lake State Park comprises the disjunct North, Central, and South Recreation areas, which are surrounded by either Corps or private lands (fig. 1). Although state and federal officials permitted access to Aspidoscelis study sites at Conchas Lake in 2000–2003, private land owners in the area did not. The latter limitation prevented GJM from searching for additional groups of A. neomexicana on the east shore of the Canadian River part of Conchas Lake and south along the river.
We assigned a code to sites inhabited by A. neomexicana at Conchas Lake consistent with those used by Walker et al. (1992: fig. 1) and we assigned a name to each site (this study; table 1, fig. 1). Each code was based on CL (= Conchas Lake) and the numerical order of the date of discovery of A. neomexicana at the site (* denotes that A. neomexicana × A. sexlineata viridis hybrids also have been collected at the site). Three sites north of the Canadian River (South of Clabberhill Ranch [CL-1*], Cove Campground [CL-13], and North of Canadian River [CL-4]) and two sites south of the river (East of Conchas Lake Levee [CL-5*] and South Recreation Area [CL-2*]) were relevant to this study (table 1). Site CL-5* included two ecological components, and CL-2* included five components (table 1). We did not observe A. sexlineata viridis at CL-13 and CL-4; however, these sites were included because assessment of the biological significance of hybridization between A. neomexicana and A. sexlineata viridis should be evaluated in the context of the extent of syntopy between these species in the larger Conchas Lake area. Straight-line distances between sites and components at Conchas Lake are given in kilometers in table 2.
The sites referenced for A. neomexicana in De Baca County included FS-1 (Fort Sumner–De Baca County Landfill) adjacent to the suburbs of Fort Sumner and FS-2 (Fort Sumner–Railroad Depot) within the city. Both De Baca County and City of Fort Sumner officials with jurisdiction over these areas facilitated this study in 2002 and 2003 by allowing access to Aspidoscelis study sites.
Field Studies at Conchas Lake and Fort Sumner
On 12 July 1988, JMW and J.E. Cordes visited the Valley–plateau-hill Component (CL-5VPH*) at East of Conchas Lake Levee (CL-5*) to acquire individuals of A. tesselata pattern classes C and D for skin histocompatibility experiments (Cordes and Walker, 2003). Among the 62 specimens collected on this date were one individual of A. neomexicana and one apparent A. neomexicana × A. sexlineata viridis hybrid (Walker et al, 1990). Subsequently, JMW and colleagues returned to the lake to study A. neomexicana and to seek additional hybrids on 12 August 1988, 3 August 1989, 7 June 1990, and 15 July 1997. These visits resulted in discovery of A. neomexicana at only two sites north of the Canadian River (e.g., CL-4) where A. sexlineata viridis was not observed. Visits to the South Recreation Area by CJC on 22–23 May 1976, 28–29 May 1978, 19 July 1981, and 28 May 1990 produced only one A. neomexicana in 1990, but no hybrids. More recently, GJM conducted fieldwork at Conchas Lake on 12–15 and 17–23 June 2000, 6–15 June 2001, 17– 18 and 20–21 August 2001, 5–9 June 2002, and 12–13 August 2003 specifically to locate syntopic associations of A. neomexicana and A. sexlineata viridis, and to search for hybrids between the two species.
Upon learning of the discovery of A. neomexicana at Fort Sumner (H.L. Taylor, personal commun.; Taylor, 2002), GJM visited the city to study the species on 12–14 July 2002, 20–23 June 2003, and 15–17 August 2003. Also, a sample of A. neomexicana was collected at our request by J. Hobart at Fort Sumner on 25 July 2002.
Sampling Methods at Conchas Lake and Fort Sumner
On 12 July 1988, JMW and J.E. Cordes sampled the Aspidoscelis guild at East of Conchas Lake Levee (CL-5*), technically outside of Conchas Lake State Park, using BB air guns with permission of personnel of the Corps of Engineers. This method resulted in collection of about 40% of the A. sexlineata viridis, 60% of the A. tesselata C and D, the only A. neomexicana, and the only A. neomexicana × A. sexlineata viridis seen and identified on that date. On 12 August 1988 additional A. tesselata C and D and the only individual of A. sexlineata viridis observed were collected using the same method. Thereafter, sampling at Conchas Lake involved use of large rubber bands to collect whiptail lizards. Unlike the less wary species A. exsanguis and A. tesselata C and D, which could be collected more often than not with rubberbands, about 75–80% of individuals of A. neomexicana and A. sexlineata viridis evaded collection, especially when only one investigator was involved. At Fort Sumner, A. neomexicana and A. sexlineata viridis were also very difficult to collect with rubberbands. In fact, our inability to collect most of the individuals of A. neomexicana and A. sexlineata viridis observed, and presumably those of A. neomexicana × A. sexlineata viridis, was the most significant limiting factor encountered in our studies at Conchas Lake and Fort Sumner.
To understand the presence and relative abundance of each species of Aspidoscelis at study sites in both areas, GJM counted the whiptail lizards encountered that were either identified to species or noted as unidentified Aspidoscelis, but not collected, on each date. We also attempted to identify the habitat features affecting the composition of Aspidoscelis guilds and those that appeared to facilitate interbreeding between A. neomexicana and A. sexlineata viridis.
The live-captured lizards used in this study (one A. neomexicana from Conchas Lake and one from Fort Sumner and one hybrid male A. neomexicana × A. sexlineata viridis from Conchas Lake) were obtained with difficulty by GJM. The live lizards were transported from New Mexico by him and subsequently shipped to CJC for color photography, karyotyping, and dispensation of tissues to HCD for electrophoretic analysis.
Specimens of Aspidoscelis referenced in this report (appendices 1–8) bear numbers representing the American Museum of Natural History (AMNH), University of Arkansas Department of Zoology (UADZ), Los Angeles County Museum (LACM), University of New Mexico Museum of Southwestern Biology (MSB), and Oklahoma Museum of Natural History (OMNH).
Internal Examination of Hybrids and Parental Species
We did not conduct internal examination of two specimens of A. neomexicana, LACM 128281 from Conchas Lake (appendix 1) and MSB 65617 from Fort Sumner (appendix 6). All other lizards listed in the appendices were examined internally for the purposes of sex determination and assessment of reproductive status.
Estimation of the Year of Hatching of Hybrids and Their Maternal Progenitor
We used the graphic method devised by JMW (Taylor et al., 2001) to depict inferences pertaining to the number of generations of hybrids of A. neomexicana × A. sexlineata viridis represented in our 2000–2003 collections from the South Recreation Area. Estimation of the age of a lizard at the time of collection was based on its snout–vent length.
Analyses of Color Patterns in Hybrids and Parental Species
At Conchas Lake, A. exsanguis, A. neomexicana, A. sexlineata viridis, and A. tesselata C and D have distinctive color patterns from hatchling through adulthood. At Fort Sumner, A. neomexicana, A. sexlineata viridis, and A. tesselata pattern class E also have distinctive color patterns throughout ontogeny. The differences among these species are based on variation in the following components: ground color, the dark dorsal pigmentation surrounding all of the pale colored components; lateral, dorsolateral, and paravertebral primary stripes and the middorsal or vertebral stripe(s), the longitudinally arrayed series of pale-colored granules extending the length of the body; fields, the dark longitudinal zones of ground color between the light stripes; bars, the elongate areas of pale pigment in the fields situated at right angles to the stripes; and spots, the rounded to irregularly shaped areas of pale-colored granules in the fields and on the stripes. Dorsal tail coloration also differs among the forms of Aspidoscelis at Conchas Lake and Fort Sumner, as does ventral coloration to a lesser extent. We initially identified all hybrids reported herein on the basis of unusual combinations of certain of the aforementioned features of color pattern.
Analyses of Scutellation in Hybrids and Parental Species
We studied meristic characters (i.e., scutellation) in selected samples of Aspidoscelis to confirm the identities of suspected hybrids of A. neomexicana × A. sexlineata viridis and to assess the morphological relationship of hybrids to the parental species and to A. tesselata C.
For each specimen, we noted the anterior extent of the left and right circumorbital scale series (complete, to junction of 2nd and 3rd supraocular scales, to a point opposite 3rd supraoculars, etc.), size of the mesoptychial scales bordering the edge of the gular fold (small, greatly enlarged, or enlarged), size of the postantebrachial scales on the posterior surface of each forelimb (granular, slightly enlarged, or enlarged), and condition of the preanal scales (one or two).
We made counts of a suite of meristic variables on each specimen used in univariate and multivariate comparisons. These characters included: GAB, granules (= scales) around midbody; OR, granules from occiput to rump; PV, granules separating the paravertebral stripes at midbody; FP, sum of the left and right femoral pores; SDL, number of subdigital lamellae on the fourth toe of the left foot; COS, sum of the left and right circumorbital scales medial to the supraocular scales; LSG, sum of the left and right lateral supraocular granules; MS, number of enlarged mesoptychial scales in the transverse row bordering the gular fold (count not possible in A. neomexicana because of lack of scale enlargement); and ILS, sum of the left and right interlabial scales.
Several authors have employed multivariate statistics to compare Aspidoscelis hybrids with their candidate parental species (Walker et al., 1994, 2000; Taylor and Walker, 1996; Walker, 1997; Taylor et al., 2001; and see Cole et al., 1988, for a species of hybrid origin). We used desktop PC based software (JMP 5.0.1.2, SAS Institute) in accordance with the JMP users' manual (SAS 2002) to perform principal component (PC) and canonical variate (CV) analyses. We used three groups of lizards from CL-2* identified on the basis of color pattern and variation in the size of the mesoptychial scales and anterior extent of circumorbital scale series (see Results) as A. neomexicana × A. sexlineata viridis (N = 13), A. neomexicana (N = 49), and A. sexlineata viridis (N = 26). Initially, we were compelled to consider the possibility that the Conchas Lake form identified by Leuck et al. (1981) and Walker et al. (1990, 1992) as an enigmatic disjunct group of A. neomexicana was possibly a new clone of A. tesselata, in which case this species would be the maternal parent of the hybrids. This reasoning accounted for the inclusion of A. tesselata C from CL-5* (N = 26 specimens with complete data) in both the CV and PC procedures. In addition, specimen UADZ 7448 from site CL-2* resembled juveniles of A. tesselata C in certain features of color pattern, raising the alternative possibility that two types of hybrids were present in samples from the site.
We followed Cole et al., (1988), Taylor and Walker (1996), and Taylor et al. (2001) in using a PC analysis to provide an unbiased multivariate comparison to results obtained from the CV analysis. Specimens are not allocated to a priori groups in the PC procedure, which was based on the correlation matrix generated from the eight meristic variables examined in each specimen (GAB, OR, PV, FP, SDL, COS, LSG, and ILS). Factors with eigenvalues greater than 1.0 were selected for interpretation in the PC model.
We used a CV analysis based on the covariation among counts of the above meristic variables to generate scores for plotting on two CV axes. This resulted in a graphic portrayal of the multivariate relationships between the four samples of Aspidoscelis from Conchas Lake chosen for the analysis. Mahalanobis distance (D2) was used to compare the patterns of meristic variation among the a priori groups in the CV analysis.
Equations generated in the CV and PC procedures were employed to obtain scores for two specimens, in addition to UADZ 7448, not assigned to a priori groups. They included UADZ 3272 (= AMNH 144085) from CL-5*, identified using univariate analyses and color pattern as an A. neomexicana × A sexlineata viridis hybrid male by Walker et al. (1990), and an unusual female specimen collected by B.E. Leuck at CL-1* (OMNH 35109). The scores of these individuals were plotted to show their group affinities in the PC and CV graphics.
Analyses of Karyotypes in Hybrids and Parental Species
We used previously published methods for preparing and studying standard giemsa-stained chromosomes from bone marrow cells (Cole, 1979). In addition to examining karyotypes of A. neomexicana previously published (see Lowe and Wright, 1966a; Dessauer and Cole, 1984; Cole et al., 1988), for this report we examined 16 cells at miotic metaphase from three apparent A. neomexicana (two from Conchas Lake and one from Fort Sumner) and 10 cells from an apparent male hybrid of A. neomexicana × A. sexlineata viridis from Conchas Lake. In addition, we examined 24 cells from five specimens of A. sexlineata viridis (four from Conchas Lake and one from Colorado) for this report.
Analyses of Allozymes in Hybrids and Parental Species
New electrophoretic data for 23 gene loci are provided, based on the same four specimens mentioned above as karyotyped for this paper (three A. neomexicana and the apparent hybrid; see appendices 2, 5, and 7). We selected the loci that are most informative for addressing the questions involved, including the loci that are diagnostic for A. neomexicana from other localities (Cole et al., 1988), with which comparisons are also made here. It was not necessary to examine proteins from additional specimens of A. sexlineata viridis for this report (see Dessauer and Cole, 1984, 1989, and unpubl.; Cole et al., 1988); our most recent dataset for A. sexlineata viridis from throughout its range includes 30 individuals.
Methodology for preparation of tissue homogenates, conducting electrophoresis, localizing specific proteins, and scoring gel phenotypes in the context of gene products followed Harris and Hopkinson (1976), Murphy et al. (1996), and particularly for North American lizards of the genus Aspidoscelis, Dessauer et al. (2000). For each locus, alleles are designated in alphabetical order according to decreasing anodal migration of their allozymes. For multilocus enzymes, loci are listed numerically in order of decreasing anodal migration of their isozymes.
RESULTS
ASPIDOSCELIS at Site Cl-1* (South of Clabberhill Ranch)
The first of the four lizards used by Leuck et al. (1981) to voucher the presence of A. neomexicana at Conchas Lake (LACM 128281) was collected in 1978 “near the entrance to the Clabber Hill [= Clabberhill] Ranch” (about 500 m south of the ranch gate; Leuck, personal commun.; Walker et al., 1992 [CL-1 on map]; fig. 1 this study). This specimen and an apparent hybrid female of A. neomexicana × A. sexlineata viridis (OMNH 35109), A. exsanguis, and A. tesselata (Leuck, personal commun.) were found in habitat described by Leuck et al. (1981) as “open Juniper-grassland on sandstone substrate.”
The part of site CL-1* investigated by GJM in 2000–2003, about 500 m northwest of the point of origin of Leuck's specimens, marked the known distributional limit of A. neomexicana north of the Canadian River and provided the only known site of syntopy between A. neomexicana and A. sexlineata viridis north of the river in San Miguel County, New Mexico. Here, sandy mesquite-invaded grassland (preferred by A. sexlineata viridis, foreground in fig. 2) merges with a hilly area with junipers (preferred by A. neomexicana, background in fig. 2). In four visits to CL-1* in 2000–2003, GJM collected 14 A. neomexicana, two A. exanguis, two A. tesselata C, and observed two A. sexlineata viridis (appendix 1). We hypothesized that the lack of a disturbed transition zone between the grassland and hill components at South of Clabberhill Ranch (fig. 2) had minimized syntopic interactions and the likelihood of hybridization between A. neomexicana and A. sexlineata viridis here. The only putative hybrid from CL-1* remains OMNH 35109 collected by B.E. Leuck and colleagues in 1978.
ASPIDOSCELIS at Site CL-13 (Cove Campground)
Aspidoscelis neomexicana was abundant at Cove Campground (tables 1, 2), the source of specimen AMNH R-151740 used in our karyotypic and electrophoretic analyses. Site CL-13 consisted of a relatively open-structured assemblage of grasses, weeds, and scattered mesquites (fig. 2). Flat topography, periodic mowing, and use by humans constituted the primary nonclimatic modifiers of habitat structure at CL-13. In three visits to the site, GJM collected 12 A. neomexicana and five A. tesselata C (appendix 2). This enclave of Aspidoscelis habitat, like most that we sampled north of the Canadian River, was temporally inhabited only by parthenogenetic species to the exclusion of A. sexlineata viridis.
ASPIDOSCELIS at Site CL-4 (North of Canadian River)
Site CL-4 is located on the north side of the Canadian River near the dam (tables 1– 3; fig. 1; appendix 3). It extends from the hilltop east of a parking lot to a bench elevated above the Canadian River, then about 500 m to the east. At North of Canadian River, we observed whiptail lizards on the hilltop, the steep south-facing hillside, the upper bench with an unpaved road and a precipice, the smaller bench at the base of the precipice, and in the roughlands area to the east of the upper bench (fig. 3). Plants at the site included combinations of grasses and other herbaceous vegetation, cacti, mesquites, and a few junipers in a gravelly and rocky substrate.
Most individuals of A. neomexicana collected and observed at CL-4 were found in a zone of about 10 m in width bordering about 100 m of the rocky precipice of the upper bench (fig. 3). Most of these lizards were found within 5 m of the edge of the precipice in the most unusual habitat known to us for A. neomexicana. In the first visit to CL-4 in 1988, JMW found only A. exsanguis and A. tesselata C on the hilltop and hillside. The part of the site preferred by A. neomexicana was not located until B.E. Leuck informed him that she had observed the species along the precipice earlier in 1988. In four out of six visits to the precipice and bench in 2000 and 2001, GJM collected four A. neomexicana, seven A. exsanguis, and seven A. tesselata C (table 3, appendix 3). We doubt that A. sexlineata viridis could become established at topographically complex CL-4. Surprisingly, A. tesselata D was not observed at CL-4, but was collected on the opposite side of the river.
ASPIDOSCELIS at Site Cl-5* (East of Conchas Lake Levee)
The first New Mexico whiptail (UADZ 3235 = AMNH 148599) and hybrid male A. neomexicana × A. sexlineata viridis (UADZ 3272 = AMNH 144085) from CL-5* were discovered at the Valley-plateau-hill component (CL-5VPH*) by JMW and J.E. Cordes in July 1988 (Walker et al., 1990). A thorough search of this component a month later in August 1988 (Walker et al., 1992) revealed no additional hybrids or individuals of A. neomexicana. The 1988 studies at CL-5VPH* at East of Conchas Lake Levee resulted in observation of a greater than 60:1 ratio of each of A. sexlineata viridis and A. tesselata to A. neomexicana. These results led Walker et al. (1990, 1992) to state that previous collectors working at CL-5* easily could have overlooked A. neomexicana based on its scarcity at the site in 1988.
Ecological characteristics of the three levels comprising the CL-5VPH* component at the south end of East of Conchas Lake Levee (fig. 4) remain essentially as described by Walker et al. (1990, 1992). At CL-5VPH* (tables 1, 4; appendix 4; fig. 4), away from the base of the plateau, the relative abundance of A. neomexicana, A. tesselata C and D, and A. sexlineata viridis are presently similar to levels observed in 1988 (Walker et al., 1992). However, recent observations by GJM indicate that both A. neomexicana and A. sexlineata viridis are now more numerous in the immediate vicinity of the middle-level manmade plateau than recorded in 1988. In five visits to CL-5VPH* in 2000–2002, GJM collected five A. neomexicana, four A. sexlineata viridis, 17 A. tesselata C, two A. tesselata D, and no hybrids.
We refer to the topographically less complex Valley component (across the levee from the Central Campground of Conchas Lake State Park) designated East of Conchas Lake Levee as CL-5V (table 1; fig. 4; appendix 4). This is a relatively stable sandy mesquite-grassland with very few A. neomexicana and with large numbers of A. sexlineata viridis. In five visits to CL-5V in 2000–2002, GJM collected two A. neomexicana, 17 A. sexlineata viridis, five A. tesselata C, two A. tesselata D, and no hybrids.
ASPIDOSCELIS at Site CL-2* (South Recreation Area)
The first report of A. neomexicana south of the Canadian River and Conchas Lake was based on specimen OMNH 35110 collected “ca. 1.25 km SSE of the town of Conchas [= Hooverville]” in 1979 (Leuck et al. 1981). This record is within the area designated as site CL-2* (Walker et al., 1992), which we here redefine to include five ecological components located in and near the South Recreation Area (tables 1, 2, 5; fig. 1; appendix 5).
Seven visits to CL-2C*, the South Campground component at CL-2* (fig. 5), by CJC in 1976–1990 resulted in collection of numerous specimens of A. sexlineata viridis, A. tesselata C, and A. tesselata D. However, it was not until the last visit to CL-2C* in 1990 that an individual of A. neomexicana was obtained by CJC (appendix 5). More recently, GJM found that A. neomexicana is now the most abundant species at the part of CL-2C* that is along a row of trees bordered by large blocks of rock among grasses and other herbaceous vegetation (fig. 5). In five out of eight visits in 2000–2003, he obtained 14 A. neomexicana, six A. sexlineata viridis, two A. exsanguis, two A. tesselata C, two A. tesselata D, and one male and two female hybrids of A. neomexicana × A. sexlineata viridis (appendix 5). We inferred that hybridization between these species occurred as they utilized the base of the rock-line for foraging, burrowing, and escape, behaviors that would presumably result in many interspecific encounters.
Immediately west of the paved road leading to the South Campground is CL-2H*, the Hill component of CL-2*, consisting of a hilltop and an east-facing hillside with modified mesquite and juniper grassland (including many clumps of yucca) in sandy soil (fig. 6). In 2000–2003, GJM found numerous A. neomexicana and a few A. sexlineata viridis on the hillside, as well as three male and four female hybrids of A. neomexicana × A. sexlineata viridis. Hybrids constituted 47.1% of the 17 Aspidoscelis collected on the hillside, including the only four lizards collected on 6 June 2002 (appendix 5). In four visits to CL-2H*, GJM also collected nine A. neomexicana and one A. sexlineata viridis.
Approximately 1 km northwest of the South Campground is CL-2J*, the Juniper Campground component of CL-2*, consisting of fragmented sandy mesquite and juniper grassland in a small heavily used recreation area (fig. 6). Clearly, A. neomexicana was much more abundant than A. sexlineata viridis in this component from which two hybrid males, including AMNH 151739 used in karyotypic and electrophoretic analyses, were collected on 7 June 2002. In three out of six visits to this component in 2001–2003, GJM also collected 20 A. neomexicana, two A. sexlineata viridis, six A. tesselata C, and one A. tesselata D.
The Lodge component (CL-2L*) is slightly elevated above the Juniper Campground component of CL-2*, and it consisted of a mowed grass-forbs association. Most of the lizards present at CL-2L* were A. neomexicana. In four visits to this component in 2000, 2001, and 2003, GJM also collected four A. neomexicana, two A. sexlineata viridis, one A. exsanguis, two A. tesselata C, one A. tesselata D, and one female hybrid A. neomexicana × A. sexlineata viridis.
ASPIDOSCELIS at Two Fort Sumner Sites
The first specimen of A. neomexicana reported from the Pecos River drainage in De Baca County was collected on 9 June 2002 at FS-1, Fort Sumner-De Baca County Landfill (table 1; fig. 7; appendix 6) in the suburbs of Fort Sumner (Taylor, 2002). Subsequently, in three visits to FS-1 in 2002 and 2003, a site consisting of frequently altered patches of roadside weeds, mounds of earth, and debris (fig. 7), GJM found syntopic associations of A. neomexicana, A. sexlineata viridis, and A. tesselata E. Both E. D. Parker (personal commun.) and JMW collected and observed only A. sexlineata viridis and A. tesselata E at FS-1 in 1973 and 1996–1998, respectively.
At FS-2, Fort Sumner-Railroad Depot, consisting of the railroad right-of-way and a bordering mesquite association (fig. 7), GJM found a large number of A. neomexicana including AMNH R-151741 used in karyotypic and electrophoretic analyses (appendix 7). In five visits to the Fort Sumner-Railroad Depot in 2002 and 2003, he observed syntopic associations of A. neomexicana, A. sexlineata viridis, and A. tesselata E.
Habitat Structure as an Extrinsic Facilitator of Hybridization Between A. NEOMEXICANA and A. SEXLINEATA VIRIDIS
At Conchas Lake, we observed syntopy between A. neomexicana and A. sexlineata viridis in about 70% of the area known to be inhabited by this parthenogen south of the Canadian River (CL-2* and CL-5*), but in only about 5% of the area known to be inhabited by this parthenogen north of the river (CL-1*). The 15 hybrids collected at Conchas Lake indicated that neither behavioral nor cytogenetic differences are perfect barriers to hybridization between A. neomexicana and A. sexlineata viridis.
Previous studies have identified two types of plant assemblages as being among the extrinsic factors that promote hybridization between certain parthenogenetic and gonochoristic species of Aspidoscelis by increasing contacts between the members of the syntopic assemblages (table 6). These include ecotonal settings (e.g., A. neomexicana × A. tigris marmorata in New Mexico, Dessauer et al. 2000; A. tesselata × A. tigris marmorata in New Mexico, Taylor et al., 2001) and weedy habitats resulting from human disturbances (e.g., A. neomexicana × A. inornata in New Mexico, Christiansen et al., 1971; A. laredoensis × A. gularis in Texas and México, Walker et al., 1989). Consistent with these observations is our finding that all of the hybrids of A. neomexicana × A. sexlineata viridis obtained in 2000–2003 from the South Recreation Area (N = 13) were found in either altered weedy assemblages or fragmented habitats (i.e., CL-2C*, CL-2H*, CL-2J*, and CL-2L*) resulting from human activities (figs. 5, 6).
Conversely, the components of site CL-5* (East of Conchas Lake Levee) represented examples of vegetational assemblages that have remained relatively stable during the past 25 years and are apparently mostly devoid of extrinsic facilitators of hybridization between A. neomexicana and A. sexlineata viridis (fig. 5). Numerous visits to CL-5* by GJM in 2000–2002 did not add to the one hybrid male obtained at the site by JMW and J.E. Cordes in 1988. Although recent collecting data indicate that A. neomexicana has increased its numbers on the small plateau at the south end of CL-5VPH* since 1988, there is no evidence that it has become more abundant in the valley below, where there has remained a large number of A. sexlineata viridis. The topographic and vegetational complexity of the Valley-plateau-hill Component at CL-5* essentially resulted in localized syntopy between A. neomexicana and A. sexlineata viridis. We found it possible to increase the number of encounters with each of the species present at CL-5* by searching different parts of the site; the mosaic distributions of mesquite with growths of grasses were more productive for A. tesselata C and D, exposed grassy areas with widely scattered mesquite for A. sexlineata viridis, and the plateau for A. neomexicana. We seldom observed A. tesselata and A. neomexicana at CL-5VPH* in the grassy exposed areas lacking shrubs; however, we did observe occasional individuals of A. sexlineata viridis in the mesquite with A. tesselata and, rarely, on the small plateau with A. neomexicana.
The Hill component, the source of 7 of 13 hybrids collected in South Recreation Area in 2000–2003, is of special interest. We observed an ensemble of ecological factors that appeared to facilitate hybridization between A. neomexicana and A. sexlineata viridis at CL-2H*. Here, we observed an occasional individual of A. sexlineata viridis in a 50 × 80 m zone of open-structured disturbed vegetation that contained about 10 times as many females of A. neomexicana. Habitat separation between the hybridizing species was not apparent at CL-2H*, and thus the few males of A. sexlineata viridis in the zone of syntopy would likely have had many encounters with females of A. neomexicana. Obviously, some of these contacts had produced the seven hybrids collected at the component in 2000–2002. Also, it is possible that the absence of other species at CL-2H* removed the potential for deflecting encounters between the hybridizing species.
Perennial Production of A. NEOMEXICANA × A. SEXLINEATA VIRIDIS Hybrids at Conchas Lake
Using SVL data and date of collection for 13 hybrids from CL-2*, we determined that they represented a minimum of four and a maximum of five generations (depending upon acceptance of either a conservative or a liberal estimate of the ages of six adult hybrids depicted in fig. 8). Although perennial hybridization between A. neomexicana and A. sexlineata viridis is indicated for the South Recreation Area as a whole (figs. 5, 6), this is not to say that collection of hybrids here necessarily can be accomplished on demand. Indeed, results from visits to CL-2* by GJM on 12 and 13 August 2003 to collect additional hybrids indicated that previous successes in obtaining hybrids were a matter of serendipity. Of the neomexicana-like lizards collected in 2003 at the South Recreation Area, only 1 was a hybrid (from the Campground component) and 24 were A. neomexicana.
Aspidoscelis neomexicana and A. tesselata possess indistinguishable hybrid-derived karyotypes consisting of a set of chromosomes from a member of the tigris species group (A. tigris marmorata for both) and a set from a member of the sexlineata species group (A. inornata for the former and A. gularis septemvittata for the latter). None of the areas of syntopy between A. tesselata and A. sexlineata viridis investigated at Conchas Lake included both the absence of habitat structural integrity and large numbers of the parthenogen mixed with small numbers of the gonochoristic form. However, close contacts between these species affording opportunities for hybridization were observed at the CL-5VPH* component at East of Conchas Lake Levee. Based on the lack of hybrids of A. tesselata and A. sexlineata viridis in our collections from this and other sites in the area, we infer that there are intrinsic barriers to hybridization between these species (i.e., body size differential, behavior, and/or cytogenetic factors) that outweigh extrinsic facilitators of hybridization. Nevertheless, such a hybrid (A. tesselata ♀ × A. sexlineata viridis ♂) was the ancestor of A. neotesselata (Neaves, 1969; Parker and Selander, 1976; Dessauer and Cole, 1989) and one was reported from Higbee, Otero County, Colorado, by Walker et al. (1994).
Sex Ratio of Hybrids Based on Internal Organs
In male specimens sexed by internal examinations, we could not identify a lizard from CL-5* and seven from CL-2* to A. sexlineata viridis, the only gonochoristic species of Aspidoscelis at Conchas Lake, because of unusual color pattern and scutellation characters. Subsequently, we identified these eight males (three adults and five juveniles) and six unusual females (three adults and three juveniles also examined internally) from Conchas Lake that resembled the males in external anatomy as hybrids of A. neomexicana × A. sexlineata viridis. A seventh female, OMNH 35109 sexed based on external anatomy, contributed to an overall sex ratio of eight males and seven females for hybrids obtained at Conchas Lake.
Color Pattern in Male Hybrids and Parental Species
Pertaining to an unusual male from CL-5* collected in 1988, Walker et al. (1990) stated that “Sharp discontinuities in color pattern distinguish Cnemidophorus neomexicanus and C. sexlineatus at all ontogenetic stages of development. Thus, the presence of male reproductive structures in a lizard with color pattern features characteristic of all-female C. neomexicanus, and never present in male C. sexlineatus, was the basis of our hypothesizing that UADZ 3272 [= AMNH 144085] is a hybrid, which would be triploid.” Further study of the color pattern of AMNH 144085 (SVL 67 mm) compared with specimens of the parental species obtained at CL-5* in 2000–2002 have reinforced the hypothesis that the AMNH specimen is a male of A. neomexicana × A. sexlineata viridis. Characters relevant to this conclusion were summarized and illustrated by Walker et al. (1990: table 1, fig. 1).
We used a male lizard captured alive (AMNH R-151739, 74 mm SVL from CL-2J*, figs. 9B, 12A) in karyotypic and electrophoretic analyses to genetically verify its hybrid genealogy. It differed from all available specimens of A. neomexicana and A. sexlineata viridis in the following features: (1) anterior 50% of the vertebral and paravertebral stripes relatively straight; (2) posterior 50% of vertebral stripe intermittently wavy and fragmented; (3) upper lateral and dorsolateral fields a very dark hue of brown; (4) spot formation in the dorsolateral fields not evident anteriorly and arrested at the earliest discernable stage posteriorly; (5) spot formation in the lower and upper lateral fields arrested at intermediate stages; and (6) sides of the head, anterior surfaces of the forelimbs, and ventral surfaces of the body a conspicuous pastel blue (now faded in alcohol). The other adult hybrid males, UADZ 7344 (SVL 61 mm from CL-2H*, fig. 12E) and UADZ 7553 (SVL 72 mm from CL-2H*, fig. 12C), possessed the same color hues described for AMNH R-151739. However, the waviness of the vertebral stripe and presence of distinct spots in the upper lateral fields in UADZ 7344 more closely resembled individuals of A. neomexicana of similar size than either of the other two adult hybrid males. We were also able to easily sort the four juvenile hybrid males from CL-2* from specimens of A. neomexicana of similar size based on these features: UADZ 7700 (SVL 36 mm from CL-2J*, not illustrated), UADZ 7561 (SVL 49 mm from CL-2J*, fig. 13A), and UADZ 7452 (SVL 37 mm from CL-2H*, fig. 13D) by their obviously straighter stripes and lack of distinct spots in any of the dark fields, and UADZ 7448 (SVL 45 mm from CL-2H*, fig. 13E) by its straighter primary stripes, intermittently fragmented vertebral stripe, and indistinct spots in the upper lateral fields. In alcohol, UADZ 7448 closely resembled juveniles of A. tesselata C in the fragmented vertebral stripe and darkly hued fields; however, in life its dark brown rather than black fields and its intense blue tail color identified the individual as A. neomexicana × A. sexlineata viridis.
Color Pattern in Female Hybrids and Parental Species
With the exception of probable hybrid OMNH 35109 from CL-1*, all specimens examined from north of the Canadian River at Conchas Lake represent A. neomexicana, A. sexlineata viridis, A. exsanguis, or A. tesselata C based on distinctive color patterns. Beth E. Leuck (personal commun.) considered the unique color pattern of OMNH 35109 collected alive in 1978 to be indicative of a hybrid origin. Although Leuck made the live lizard available to J.W. Wright for karyotyping, that did not occur. Our examination of the preserved specimen revealed it to be darkened, presumably by formalin; however, a superb color slide of the dorsal color pattern of the live lizard was made available to us by B.E. Leuck (represented in fig. 10).
We compared OMNH 35109 with a pooled sample of 37 A. neomexicana (e.g., fig. 11A) from sites north of the Canadian River (CL-1*, CL-13, and CL-4) that included a minimum of four year classes (SVL 36– 80 mm). Each specimen in the pooled sample had the dorsal pattern (spots and wavy stripes) and ventral coloration typical of this parthenogenetic species except for UADZ 7532 (SVL 38 mm) from CL-1*, which had a black-pigmented throat unlike any other individual of A. neomexicana known to us from throughout its range. However, we did not consider UADZ 7532 to be a hybrid based on its total ensemble of color pattern and scutellation characters. Conversely, we found OMNH 35109 to be quite unlike all adult females in the pooled sample, and it seemed appropriate to embrace B.E. Leuck's hypothesis of an A. neomexicana × A. sexlineata viridis genealogy for the individual.
The alternative hypothesis that this unusual specimen (OMNH 35109; SVL 69 mm; fig. 10) is merely an “outlier” of A. neomexicana based on an aberrant dorsal color pattern, as verified in the case of AMNH 125547 from Hidalgo County, New Mexico, by Dessauer and Cole (1989), is not supported by its ventral color pattern and results from univariate and multivariate analyses of scutellation. In life, ONMH 35109 was characterized by (1) unspotted brown fields, (2) lateral stripes represented by a longitudinal array of lichenoid components, (3) dorsolateral and paravertebral stripes with unusually wavy edges, (4) vertebral stripe of extreme waviness (interrupted anteriorly and with extensions that touch the paravertebral stripes), (5) indistinctly patterned gray-tan-brown hindlimbs, (6) a gray-tan tail, and (7) sky blue ventral surfaces.
We identified three adult and three juvenile hybrid females of A. neomexicana × A. sexlineata viridis from CL-2* (South Recreation Area). Among the adults, UADZ 7554 is an unusually large female (SVL 79 mm from CL-2H*, fig. 12D) with a color pattern that is intermediate between the parental forms. It has (1) straight stripes on the anterior 50% of the body, (2) gray-brown fields, (3) only the faintest indication of spot formation in the fields, and (4) gray-blue ventral surfaces. Hybrid female UADZ 7445 (SVL 69 mm from CL-2L*, fig. 12B) has slightly more distinct spots than does UADZ 7554 (fig. 12D), and it has a greater overall resemblance to A. neomexicana in the character of the stripes. The most distinctive feature of hybrid female UADZ 7349 (SVL 64 mm from CL-2C*, fig. 12F) involved the waviness and interconnections of the paravertebral and vertebral stripes and distinct spots in the upper lateral fields. Three juvenile females (UADZ 7561, SVL 49 mm from CL-2J*, fig. 13A; UADZ 7555, SVL 47 mm from CL-2H*, fig. 13C; UADZ 7455, SVL 48 mm from CL-2C*, fig. 13F) were initially sorted from juveniles of A. neomexicana on the straightness of their paravertebral stripes and unusual vertebral stripes.
Univariate Analyses of Scutellation in Hybrids and Parental Species
In 96 specimens of A. neomexicana from five sites at Conchas Lake (CL-1*, CL-13, CL-4, CL-5*, and CL-2*), the first several transverse rows of scales anterior to the edge of the gular fold were very small and there were no groups of countable enlarged mesoptychials (the scales along the edge of the gular fold, fig. 14A, B), with the size of the scales being completely diagnostic compared with A. sexlineata viridis (fig. 14C). In 49 A. sexlineata viridis from Conchas Lake (CL-5* and CL-2*) the mesoptychial scales were arrayed in three subtly different patterns: (1) a transverse row of very small scales preceded by a row of abruptly enlarged scales, (2) more than four small scales intermittently appearing between the posterior edges of enlarged scales, and (3) only one to three small scales along the gular fold between the posterior edges of enlarged scales (fig. 14C). In the eight hybrid males and seven hybrid females from Conchas Lake the mesoptychial scales closely resembled conditions 1 and 2 described for A. sexlineata viridis except for being slightly smaller; they differed from A. neomexicana in their much larger size and distinctive arrangement (fig. 14D, E).
All individuals of A. neomexicana had circumorbital series that extended farther anteriorly than in A. sexlineata viridis; the two species could be distinguished on this character alone. Variation for circumorbital series in specimens of A. neomexicana from five sites at Conchas Lake is summarized in table 7. Among specimens of A. neomexicana the circumorbital scale series were complete on both sides of the head in 47/96 (49.0%), complete on only the left side in 12/96 (12.5%), complete on only the right side in 3/96 (3.1%), and incomplete on both sides in 34/96 (35.4%). Among 49 individuals of A. sexlineata viridis from Conchas Lake (CL-5* and CL-2*) the circumorbital scale series extended as far anteriorly as the middle of the third supraocular scales in only one specimen; the series terminated more posteriorly either near the middle of the fourth supraocular scales or at the suture between the third and fourth supraoculars in the other specimens. All hybrid males had incomplete circumorbital scale series that resembled individuals of A. neomexicana with incomplete series rather than resembling A. sexlineata viridis with short series (tables 7–10).
Variation for the one (N = 62, 64.6%) or two (N = 34, 35.4%) preanal scale character states in specimens of A. neomexicana from five sites at Conchas Lake are summarized in table 7 (= suture patterns of Dessauer and Cole, 1989; they reported one female with one preanal from Sandoval County that produced two neonates with one scale and two neonates with two scales). In A. sexlineata viridis there were two preanal scales immediately anterior to the vent in 48/49 specimens from CL-5* and CL-2*; the other specimen had one preanal scale. Fourteen hybrids from CL-5* and CL-2* resembled A. neomexicana in usually having one preanal scale (N = 10, 71.4%) rather than two (N = 4, 28.6%) scales (table 7).
In summary, all male and female hybrids of A. neomexicana × A. sexlineata viridis possessed enlarged mesoptychial scales (fig. 14C, D) and incomplete circumorbital series along with color patterns that resembled the maternal parent (figs. 9, 11–13). We reexamined all specimens with incomplete circumorbital series and small mesoptychial scales and there were no changes in our conclusion that all were examples of A. neomexicana rather than some being cryptic hybrids.
Univariate comparisons were quantitatively extended to eight meristic characters and the PV/GAB ratio in the pooled samples of A. neomexicana, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis hybrids (excluding OMNH 35109 from CL-1*) from Conchas Lake. The OR character was not significantly different among any of the three samples. The GAB, PV/GAB, SDL, COS, and LSG characters differed significantly among all samples. The sample of hybrids differed from A. neomexicana in the GAB, PV, SDL, COS, and LSG and from A. sexlineata viridis in the GAB, FP, SDL, COS, LSG, and ILS (PV/GAB not included in table 9). Means for the sample of hybrids were intermediate to the parental forms in the LSG, COS, FP, SDL, PV, and PV/GAB, higher than both parental forms in the OR and ILS, and lower than both parental forms in the GAB (table 9). The low variability that we hypothesized for parthenogenetic A. neomexicana as a consequence of clonal reproduction and the high variability expected in A. sexlineata viridis as a result of gonochoristic reproduction were confirmed by three aspects of the univariate statistics. First, COV values for A. neomexicana were lower for each character than the COV values for A. sexlineata viridis (tables 8, 9). The sample of hybrids was intermediate to the parental species in COV values for more than half of the characters, but not in the ILS, GAB, FP, and PV/GAB. Second, ranges of variation for the OR, GAB, FP, and SDL in A. sexlineata viridis were about twice those for the same characters in both A. neomexicana and the hybrids. Third, we used the Shapiro-Wilk W Test of Normality for data dispersions by variable to identify normal (N) and not normal (NN) distributions for the following characters in each pooled sample (table 9): A. neomexicana (N, OR and ILS; NN, GAB, PV, FP, SDL, COS, and LSG); A. neomexicana × A. sexlineata viridis (N, GAB, OR, FP, SDL, LSG, and ILS; NN, PV and COS; and A. sexlineata viridis (N, GAB, OR, LSG, and ILS; NN, PV, FP, SDL, and COS). The relationship between parthenogenetic reproduction and NN data dispersions in A. neomexicana is reflected in a preponderance of characters with narrow ranges of variation and leptokurtic distribution yet the hybrids had mostly N data dispersions. The NN distributions for several characters in A. sexlineata viridis reflect wide ranges of variation and curves with positive or negative skews.
We also conducted a by-site comparison of eight meristic variables and a ratio for five samples of A. neomexicana (CL-1*, CL-13, and CL-4 located north of Canadian River; CL-5* and CL-2* located south of river), two samples of A. sexlineata viridis (CL-5* and CL-2*), and male and female hybrids (CL-5* and CL-2*) (table 10). There were no significant intraspecific differences for any pair of means among the samples of either A. neomexicana or A. sexlineata viridis, and no sexual dimorphism was apparent between male and female hybrids. The ranges of differences among means for nine variables in five samples of A. neomexicana followed by two of A. sexlineata viridis are: GAB, 1.4 and 1.9; OR, 4.5 and 7.0; PV, 0.9 and 0.8; PV/GAB, 1.0 and 0.8; FP, 1.0 and 0.3; SDL, 0.9 and 0.3; COS, 1.3 and 0.5; LSG, 2.8 and 2.4; and ILS, 4.4 and 3.0. The COS mean for the sample of A. neomexicana from CL-2* (N = 49) obscures variation, which was discussed previously. In fact, specimens collected in 2003 at this site necessitated reevaluation of our seemingly robust hypothesis that specimens from CL-5* (N = 1) and CL-2 (N = 13) collected in 1988–2002 with color patterns similar to A. neomexicana, incomplete circumorbital scale series on both sides of the head, and enlarged mesoptychial scales along or near the edge of the gular fold represented A. neomexicana × A. sexlineata viridis hybrids. The sample of specimens of A. neomexicana from CL-2* collected prior to 2003 (N = 26) included 15 specimens with complete circumorbital series on both sides, four with complete series on only the left side, and seven with incomplete series on both sides, all with typical color patterns and small mesoptychial scales. The sample of the species obtained in 2003 (N = 25) included 7 specimens with complete circumorbital series on both sides, 2 with complete series on only the left side, 2 with complete series on only the right side, and 14 with incomplete series on both sides. We were compelled to reexamine each specimen in the 2003 sample of A. neomexicana from CL-2* to determine if some of the individuals with incomplete circumorbital series were actually hybrids. This analysis resulted in identification of one probable hybrid (presence of incomplete circumorbital series on both sides and large mesoptychial scales) among the 25 specimens, with all other specimens having mesoptychial scales and color patterns typical of A. neomexicana.
Multivariate Analysis of Scutellation In Hybrids and Parental Species
Principal Components Analysis (PCA):
The PCA revealed that the first two principal components represented a remarkably high 78.3% of the variation included in the eight characters of scutellation (GAB, OR, PV, FP, SDL, COS, LSG, and ILS) used in this multivariate analysis of samples of A. neomexicana, A. neomexicana × A. sexlineata viridis, A. sexlineata viridis, and A. tesselata from Conchas Lake. Significant differences among all sample scores for the first principal component (employing these variables as univariate characters) were noted; however, not all scores were significantly different for the second principal component. Comparison of component loadings (table 11) to characters with nonsignificant differences between hybrids and one of the parental species (table 9) indicated that the first principal component reflected similarities of hybrids to A. neomexicana in number of femoral pores. The second principal component reflected similarities of hybrids to A. neomexicana in number of interlabial scales and to A. sexlineata viridis in number of granules separating the paravertebral stripes.
The multivariate pattern of variation was depicted in an ordination of principal components scores on the first two axes (fig. 15). There was some overlap in PCA scores representing both of the parental species and the hybrids, but no overlap between those scores and A. tesselata, based on the 95% confidence limits. This pattern is consistent with the assumption of a hybrid origin for the specimens involving the maternal parental species A. neomexicana and paternal parental species A. sexlineata viridis.
Canonical Variate (CV) Analysis:
We used a linear CV analysis based on the same characters of scutellation used in the PCA to further assess the multivariate relationships of four a priori groups, the A. neomexicana × A. sexlineata viridis hybrids and their possible parental species A. neomexicana, A. tesselata, and A. sexlineata viridis. The CV analysis not only assigned each specimen to its predicted a priori group, but the plots of CV scores for each species on standardized discriminant axes were widely separated (fig. 16). All putative hybrids from CL-2* were also assigned to predicted a priori group, and the plot of CV scores for these individuals added weight to our conclusion that all of them represented the morphologically intermediate progeny of A. neomexicana females that had been inseminated by A. sexlineata viridis males and that they were, as expected, morphologically closer to their maternal parent (fig. 16). The CV scores generated for two additional putative hybrids, from sites CL-1* (OMNH 35109) and CL-5* (AMNH 144085), were contained within the 95% ellipse for the hybrids from CL-2*. The first two canonical variates explained 95.9% of the variation (table 11).
Mehalanobis distances (D2) among centroids of the four a priori groups provided a quantitative measure of multivariate resemblance among hybrids and the other species analyzed (table 12). The hybrids were closer to A. neomexicana (D2 = 25.9, 2 of 3 sets of shared chromosomes) than to A. sexlineata viridis (D2 = 68.1, 1 set of shared chromosomes). In comparison, the D2 value between A. neomexicana and A. sexlineata that share no chromosomes was 101.6. Hybrids OMNH 35109 and AMNH 144085 had D2 values comparable to that of the 13 hybrids from CL-2*.
Karyotypes of a Hybrid and Parental Species
Clearly resolved karyotypes of the allodiploid A. neomexicana have been published previously and are consistent with its hybrid origin involving A. tigris marmorata × A. inornata (Lowe and Wright, 1966a; Parker and Selander, 1984; Cole et al., 1988). Aspidoscelis tigris marmorata and A. inornata belong to the tigris and sexlineata species groups, respectively (Lowe et al., 1970; Reeder et al., 2002). Each species group has a diagnostically distinct karyotype (Lowe et al., 1970).
The A. tigris marmorata complement (n = 23) consists of 3 large Set I biarmed macrochromosomes + 8 smaller Set II biarmed intermediate-sized macrochromosomes + 12 Set III microchromosomes. The second largest chromosome in Set I of A. tigris has a dotlike satellite on the end of one arm, which is often difficult to see, and the third largest chromosome is the sex chromosome (Cole et al., 1969; Bull, 1978) of which the X-chromosome is recognizable in the karotype of A. neomexicana. The complement from A. inornata (n = 23) consists of only one large Set I metacentric macrochromosome (with a subterminal secondary constriction on one arm followed by an elongate satellite) + 12 smaller Set II intermediate-sized telocentric or subtelocentric macrochromosomes + 10 Set III microchromosomes. The sex chromosomes of A. inornata are not morphologically recognizable. The secondary constrictions on the Set I chromosomes of both A. tigris and A. inornata are the nucleolar organizer regions (Ward and Cole, 1986).
As expected, the three putative representatives of A. neomexicana (AMNH R-136881, R-151740 from Conchas Lake, and R-151741 from Fort Sumner) had a diploid karyotype consisting of one normal tigris group haploid complement and one normal sexlineata group haploid complement of chromosomes, or 2n = 46. Consequently, karyotypes are consistent with the assumption that these specimens are correctly identified as A. neomexicana from both localities. However, the karyotype is not diagnostic, as the karyotype of A. tesselata from Conchas Lake is identical (Dessauer and Cole, 1989: 57). Nevertheless, the proteins do confirm the identity of these A. neomexicana (see below). In addition, the five A. sexlineata viridis examined all had the normal sexlineata group karyotype, and each had a distinctive subtelocentric pair of Set II chromosomes that characterizes this species (Bickham et al., 1976), although CJC's data suggest that there is only one of these distinctive Set II pairs (about the fourth largest Set II pair), instead of two as reported by Bickham et al. (1976).
The suspected hybrid male (AMNH R-151739) from Conchas Lake was a triploid having 3n = 69 chromosomes, including the full diploid karyotype of A. neomexicana plus a second haploid complement of sexlineata group chromosomes (fig. 17). In all details of the karyotype, this triploid appeared to be an F1 hybrid of A. neomexicana × A. sexlineata viridis. In addition, the karyotype was identical to that of the laboratory-produced hybrid of A. neomexicana × A. sexlineata reported by Dessauer and Cole (1984). Based on the morphology of this karyotyped individual, we infer that five additional males (AMNH 144085, GM [at UADZ] 128, 279, 412, 430) from Conchas Lake with color patterns largely resembling A. neomexicana are also F1 hybrids between these species.
Allozymes of a Hybrid and Parental Species
Based on genotypes detected at 23 loci, we obtained evidence bearing on the following questions: (1) Were the specimens of suspected A. neomexicana from Conchas Lake (AMNH R-136881, R-151740) and Fort Sumner (AMNH R-151741) actually this species and not something else similar to that, such as a new color pattern class of A. tesselata? (2) Was the suspected hybrid (AMNH R-151739) actually that? (3) Was the male parent of the hybrid a representative of A. sexlineata viridis?
The two A. neomexicana examined from Conchas Lake and Fort Sumner had identical genotypes at each of the 23 loci (table 13), except for one allele in the lizard from Fort Sumner. Twelve or 13 loci (52–56%) had alleles in the heterozygous state, attesting to the ultimate origin of this taxon from a hybridization event (A. tigris marmorata ♀ × A. inornata ♂). In addition, the specimen from Conchas Lake appeared to be identical (all loci, all alleles) to specimens of the most common and most widely distributed clone of A. neomexicana from elsewhere in its geographic range (table 13; Cole et al., 1988). In particular, the two orphan alleles known to characterize A. neomexicana from other localities appeared to be present in the specimens from both Conchas Lake and Fort Sumner. These are the very distinctive d-allele at ESTD (fig. 18) and c-allele at PEPB (also normally found in A. sexlineata viridis; table 13; appendix 8; Cole et al., 1988).
The specimen of A. neomexicana from Fort Sumner was identical to the one from Conchas Lake, excepting one allele. It differed only by possessing one b-allele at sMDH (heterozygous ab, fig. 18). It would be interesting to compare this b-allele with the variant sMDH allele found by Parker and Selander (1984) to occur infrequently in A. neomexicana in the vicinity of Engle, Sierra County, New Mexico.
Normally, A. neomexicana and A. tesselata (including those from Conchas Lake) differ at the following 10 loci among those examined for this report: sMDH, sMDHP, sIDH, ESTD, PEPA, PEPB, ADA, MPI, GPI, and PGM2 (Dessauer and Cole, 1989, and unpubl.). Clearly (table 13), the new specimens we examined for the present report that appeared to be A. neomexicana are correctly identified as representing that taxon and are not a new clone of A. tesselata (table 13).
Of the 23 loci analyzed (table 13), 9 showed no allelic variation among the individuals of each taxon and the hybrid examined (the same alleles were shared universally), but 12 loci were particularly informative for identifying the hybrid and its parental species. For nearly each of these loci, the suspected hybrid (based on morphology and triploid karyotype) had electrophoretic banding patterns consistent with a triploid bearing a combination of alleles that included the two found in the diploid A. neomexicana plus a third allele from the local A. sexlineata viridis. This is consistent with a cloned neomexicana ovum having been fertilized by a haploid sexlineata spermatozoan (table 13).
The presence of the sexlineata allele in the hybrid was detected at most loci based on allele dosage effects on band densities (isozyme activities) in electrophoretic phenotypes. For example, at PEPA, specimens of the diploid A. neomexicana, which are heterozygotes (ac), show a three-banded pattern. The hybrid shows the same three bands, but the relative band densities differ from those of neomexicana. Phenotypes (gel patterns) predicted for the ac genotype of this dimeric enzyme by the expansion of (a + c)2, which equals a2 + 2ac + c2, consist of three isozymes with a ratio of activities (band densities on gels) approximating 1:2:1, as observed for neomexicana (fig. 18). The phenotype predicted for the aac genotype, predicted by the expansion of (2a + c)2, which equals 4a2 + 4ac + c2, consists of the same three isozymes but with a ratio of activities approximating 4:4:1, as observed in the triploid hybrid (fig. 18). Consequently, neomexicana and the hybrid had three-banded patterns for PEPA, but the ratio of the band densities differed between them. For A. sexlineata viridis, the b-allele is the most common one at PEPA (table 13; Cole et al., 1988), so the second a-allele found in the hybrid indicates that the a-allele occurs rarely in A. sexlineata viridis.
Similarly, LDH1 showed the same bands of isozymes in A. neomexicana and the hybrid, but there were differences in the band densities owing to the extra b-allele in the triploid contributed by A. sexlineata viridis. LDH1 is a tetrameric enzyme for which neomexicana is heterozygous (ab). The phenotype expected for the ab genotype of A. neomexicana, predicted by the expansion of (a + b)4 = a4 + 4a3b + 6a2b2 + 4ab3 + b4, is for five isozymes with a ratio of activities approximating 1:4:6:4:1 (fig. 18). The phenotype predicted for the abb triploid genotype of the hybrid, predicted by the expansion of (a + 2b)4 = a4 + 8a3b + 24a2b2 + 32ab3 + 16 b4, shows the same five isozymes but correspondingly different band-densities, as expected (fig. 18).
Banding patterns for TF and ESTD, however, involved differences in both the number of isozymes and the band densities present in A. neomexicana versus the hybrid. TF is a monomeric enzyme, so the bc genotype of neomexicana shows two more-or-less equally dense bands (fig. 18). However, the abc triploid genotype of the hybrid shows three bands (fig. 18), and the a-allele at TF is one that is common in specimens of A. sexlineata viridis from New Mexico and Colorado. At ESTD, a dimeric enzyme, specimens of the diploid A. neomexicana, which are heterozygotes (bd), show a three-banded pattern. However, the hybrid shows a five-banded pattern. Phenotypes predicted for the bd genotype of this dimeric enzyme by the expansion of (b + d)2, which equals b2 + 2bd + d2, consist of three isozymes with a ratio of activities approximating 1:2:1, although the b-band is more active than the d-band in neomexicana (fig. 18). The phenotype predicted for the abd genotype, predicted by the expansion of (a + b + d)2, which equals a2 + 2ab + b2 + 2ad + 2bd + d2, consists of six isozymes with a ratio of activities approximating 1:2:1:2:2:1. Five bands were resolved presumably because the b2 and 2ad isozymes have the same migration rate and were superimposed on the gel (fig. 18), and band densities still reflect the greater expression of the b-allele, as in A. neomexicana.
DISCUSSION
Biochemical genetic data for one lizard from Fort Sumner (AMNH R-151741) and one from Conchas Lake (AMNH R-136881) verified that the isolated groups from which they were collected were correctly identified to A. neomexicana based on morphology in the respective reports of their discovery by Leuck et al. (1981) and Taylor (2002). The data indicated that Conchas Lake A. neomexicana belongs to the most widely distributed clone of the species in New Mexico (Parker and Selander, 1984; Cole et al., 1988), and that the Fort Sumner population contains a variant sMDH allele which may be the same one found by Parker and Selander (1984) in some individuals of the species from the vicinity of Engle, Sierra County, New Mexico.
Aspidoscelis neomexicana comprises the cloned descendants from hybrid event(s) between one or more females and males, respectively, of the divergent taxa A. tigris marmorata and A. inornata (Lowe and Wright, 1966b; Parker and Selander, 1984; Cole et al., 1988; Densmore et al., 1989). Although the gonochoristic progenitors of A. neomexicana still occur in syntopy at numerous sites in desert-grassland communities in Texas and New Mexico, there have been no reports of contemporary F1 hybrids between moderately large-bodied A. tigris and small-bodied A. inornata (Cole et al., 1988). It is possible that a single hybrid female (i.e., the first A. neomexicana) founded the tokogenetic array known to occur over most of the range of the species, which comprises a single allozyme clone (Parker and Selander, 1984; Cole et al., 1988) of mutually histocompatible individuals (Cuellar, 1977; Cordes et al., 1990). Moreover, it is likely that the two additional allozyme clones of A. neomexicana (Cole et al., 1988) were produced from the original clone by mutation or recombination. That the New Mexico Whiptail is a successful parthenogenetic species despite its low clonal diversity is evidenced by both ecological and zoogeographic data (Axtell, 1966; Wright and Lowe, 1968; Cole et al., 1988; Cordes et al., 1989).
There are at least three historical obstacles to formation of new all-female species of Aspidoscelis from hybridizing species. First, the production of hybrids between gonochoristic species of Aspidoscelis, exclusive of instances of secondary intergradation which some authors have referred to as hybridization, is so rare that none has been identified to date. Second, there is no evidence of parthenogenetic capability in any of the many F1 hybrids between a parthenogenetic and a gonochoristic species that have been described in the literature, indicating that few hybrids are capable of founding tokogenetic arrays. Third, the odds would seem to be insurmountable against establishment of a new hybrid-derived parthenogenetic species in competition with both of its parental forms and other syntopic congeners. Nevertheless, in the case of A. neomexicana the parthenogenetic descendants of the original hybrid female (i.e., the first few generations) somehow overcame these odds and became established at a site inhabited by A. tigris marmorata and A. inornata. One model to account for the success of the early generations of this “general purpose” genotype that has spread to inhabit most of the range of A. neomexicana was outlined by Dessauer and Cole (1989: 52): “… an ability of one clone of C. neomexicanus to tolerate different local habitats may have prevented its immediate extinction following its hybrid origin in desert-grassland: ‘gallery forests along the Rio Grande could have had an important role in the survival of this nascent species of instantaneous hybrid origin, by providing sites for parthenogenetic hybrids to reproduce with minimal interference from the ancestral males of both species, which generally avoid the gallery forests’ (Cole et al., 1988, p. 35).” Today, sites inhabited by this parthenogen are mostly associated with the Rio Grande and some of its tributaries and adjacent playas in New Mexico and Texas (Axtell, 1966; Wright and Lowe, 1968; Cuellar, 1977; Cordes et al., 1989). In time, A. neomexicana became integrated into diverse guilds of whiptail lizards (e.g., those at Conchas Lake and Fort Sumner) consisting of variable combinations from among three gonochoristic species (A. tigris marmorata, A. inornata, and A. sexlineata viridis) and four parthenogenetic species (A. exsanguis, A. tesselata, A. uniparens, and A. velox) (table 1).
Several investigations have focused on the biological significance of perennial hybridization between a normally parthenogenetic species and one of its progenitors: A. laredoensis ♀ × A. gularis gularis ♂ (Walker et al., 1989; Paulissen et al., 1992; Walker et al., 2004) and A. tesselata ♀ × A. tigris marmorata ♂ (Taylor et al., 2001). These studies reported no indication that interspecific hybridization has had a substantial biological impact on any of the species involved. Moreover, the observations that A. laredoensis, A. neomexicana, and A. tesselata have all progressed to the final stage in the evolution of a hybrid-derived parthengenetic species of Aspidoscelis as allodiploids, namely “capture of a habitat” (Wright and Lowe, 1968), constitute a priori evidence of their avoidance of destabilizing hybridization with their gonochoristic progenitors during the first few generations of the “establishment stage”.
Discovery of natural hybrids of A. neomexicana × A. sexlineata viridis at Conchas Lake in five different years between 1988 and 2003 represents the first evidence of perennial hybridization between a parthenoform and a gonochoristic species other than one of its progenitors. Although A. neomexicana and A. sexlineata viridis hybridize at CL-2* at a frequency approaching that reported for A. neomexicana and A. inornata (Christiansen et al., 1971) and A. tesselata and A. tigris marmorata (Taylor et al., 2001), these examples of “occasional hybridization”, similar to some cases described by Mayr (1963) for gonochoristic species, apparently have had no significant negative biological consequences on the species involved. At Conchas Lake, this conclusion was based on annual observations of large numbers of juveniles of A. neomexicana in 2000–2003 by GJM at all sites and ecological components where A. neomexicana was found in syntopy with A. sexlineata viridis. Although A. neomexicana and its much larger maternal progenitor A. tigris marmorata may well have existed in syntopy at various sites for thousands of years, it appears that hybridization between these species remains quite rare as only two of their hybrids, both sterile females, have been reported (Dessauer et al., 2000). Both of these hybrids were detected during electrophoretic analyses of hundreds of specimens of A. tigris from Hidalgo and Grant Counties with which the hybrids had been confused at the time of collection based on locally variable color patterns. Conversely, the substantial number of sites from which hybrids between A. neomexicana and its smaller paternal progenitor A. inornata have been reported (Axtell, 1966; Taylor and Medica, 1966; Wright and Lowe, 1967; Christiansen and Ladman, 1968; Christiansen et al., 1971; Cuellar and McKinney, 1976; Taylor and Walker, 1996) indicates that these species have engaged in a low frequency of hybridization for countless generations without apparent genetic consequences to either species and without formation of a new allotriploid species.
The disjunct populations of A neomexicana at Fort Sumner and Conchas Lake raise perplexing questions: Do they represent introductions by humans, zoogeographic relicts, or naturally occurring peripheral groups (contiguous or not with the principal range of the species)? Even the coauthors of this report have not been of one mind on the mode of origin of A. neomexicana at Conchas Lake. If it was introduced to the area as hypothesized by Leuck et al. (1981), Cole et al. (1988), Densmore et al. (1989), and Persons and Wright (1999), then the potential for hybridization with A. sexlineata viridis in San Miguel County is very recent, involving only 15–30 years. The basis of earlier dates is that the species was not included in a large sample of whiptail lizards collected there by E.D. Parker [personal commun.] in 1973; the basis of later dates is the 1988 collection of the hybrid reported by Walker et al. (1990). If A. neomexicana is naturally occurring in the area as others have hypothesized (Walker et al., 1990, 1992; Taylor, 2002), then the potential for hybridization with A. sexlineata viridis in San Miguel County has continued over many generations. Both sides of the argument pertaining to the hypothesis of a human introduction of A. neomexicana at Conchas Lake are summarized in table 14. Two points based on observations that postdate the initial discovery of the species at Conchas Lake seem particularly relevant to the debate. First, it seems unlikely that the complex distribution pattern of the species in evidence at sites both north (e.g., CL-1* and CL-4) and south (e.g., CL-5* and CL-2*) of the river and lake as early as 1979, following its initial discovery in 1978 (Leuck et al., 1981), could have developed from either accidental or purposeful human point releases. Second, the recent discovery of the species in Fort Sumner, De Baca County, New Mexico partially bridged a previously supposed hiatus between Conchas Lake and the Rio Grande Valley (Taylor, 2002).
Evolution of a new triploid species from an A. neomexicana × A. sexlineata viridis hybrid is an intriguing possibility. As previously noted, the karyotypes of A. tesselata (A. tigris marmorata × A. gularis septemvittata) and A. neomexicana (A. tigris marmorata × A. inornata) at Conchas Lake are not diagnostic, with each species having one haploid complement from a member of the tigris species group and one from a member of the sexlineata species group (Cole et al., 1988: 22, fig. 7; Dessauer and Cole, 1989: 57, fig. 17). That is not to say that the two species are not readily distinguishable on the basis of allozymes and/or morphology. That the potential existed for incorporation of the basic diploid neomexicana or tesselata chromosome complement into a triploid karyotype with a complement from a third species is verified by the existence of A. neotesselata. That this potential was not realized for thousands of years until A. tesselata had spread from its presumed site(s) of origin in southern Texas or northern Mexico to the northern periphery of its range near Higbee, Otero County, Colorado, and that one or more hybridizations between A. tesselata × A. sexlineata viridis resulted in A. neotesselata are noteworthy. Moreover, the existence of A. neotesselata, which inhabits a restricted range in a four-county area of Colorado, suggests that a single chromosome complement from A. tigris can be incorporated into the triploid karyotype of a parthenogen in contrast to two complements from this species. This phenomenon could explain the basis for the perennial production of sterile triploid hybrids of A. tesselata × A. tigris marmorata at Arroyo del Macho, Chaves County, New Mexico (Taylor et al., 2001).
SUMMARY AND CONCLUSIONS
1. The easternmost groups of Aspidoscelis neomexicana in New Mexico were discovered at Conchas Lake, San Miguel County, by B.E. Leuck and colleagues in 1978 and at Fort Sumner, De Baca County, by H.L. Taylor in 2002. Available evidence indicates that both groups are disjunct from each other and from representatives of the species to the west in the Rio Grande Valley of New Mexico.
2. Whether A. neomexicana is naturally occurring or a human introduction at Conchas Lake has remained a point of contention based on the evidence and observations emphasized by different investigators (reviewed herein).
3. The only known sites of syntopy between parthenogenetic A. neomexicana and gonochoristic A. sexlineata viridis are in New Mexico where the eastern range limits of the former and the western range limits of the latter overlap at Fort Sumner in the Pecos River drainage and at Conchas Lake in the Canadian River drainage.
4. At the two sites in Fort Sumner where it has been observed, A. neomexicana is syntopic with both A. sexlineata viridis and A. tesselata E. At Conchas Lake, site-specific habitat characteristics have resulted in syntopic associations of various combinations of diploid A. neomexicana, A. tesselata C and/ or D, A. sexlineata viridis, and triploid A. exsanguis, with most sites of syntopy between A. neomexicana and A. sexlineata viridis being situated south of the lake and Canadian River (i.e., CL-2* and CL-5*).
5. This paper includes the first data establishing perennial hybridization between an allodiploid parthenoform (A. neomexicana) and a gonochoristic species (A. sexlineata) other than one of its progenitors (= A. tigris marmorata × A. inornata).
6. The only hybrid of A. neomexicana × A. sexlineata viridis, a female, from north of the Canadian River at Conchas Lake was collected at South of Clabberhill Ranch (site CL-1*) in 1978 by B.E. Leuck. Subsequently, seven males and seven females of A. neomexicana × A. sexlineata viridis were collected in 1988 and 2001–2003 from south of the river and lake at East of Conchas Lake Levee (site CL-5*, N = 1) and South Recreation Area (site CL-2*, N = 13).
7. The most apparent extrinsic facilitators of hybridization between A. neomexicana and A. sexlineata viridis at various components of CL-2* (South Recreation Area) were ecological in nature, based on the presence of these species and their hybrids in either altered weedy assemblages or fragmented habitats resulting from human activities.
8. Based on estimates of the age of 13 hybrids of A. neomexicana × A. sexlineata viridis from Conchas Lake using SVL and date of collection for each, four to five generations of hybrids were identified, indicating that interbreeding between these species is a perennial occurrence in various components of South Recreation Area (CL-2*).
9. All hybrid males of A. neomexicana × A. sexlineata viridis obtained at Conchas Lake (only AMNH R-151739 was karyotyped and electrophoretically analyzed) were initially identified based on the presence of male reproductive structures in individuals with color patterns resembling A. neomexicana rather than A. sexlineata viridis. Subsequent laboratory examinations revealed that hybrid males typically differed from A. neomexicana, the only parental species with which they would likely be confused, in three (juveniles) to four (adults) key components of color pattern (dorsal ground color, condition of the middorsal stripe, presence and/or number of dorsal spots, and ventral coloration) and in three characters of scutellation (distinctly larger size of the mesoptychial scales, incomplete circumorbital scale series, and reduced number of granules around midbody).
10. Eight individuals identified as hybrid females of A. neomexicana × A. sexlineata viridis were characterized by essentially the same characters of color pattern and scutellation used in recognizing male hybrids.
11. Univariate comparisons of A. neomexicana × A. sexlineata viridis, A. neomexicana, and A. sexlineata viridis revealed no significant differences among the three in the OR character, significant differences among all three in the GAB, SDL, COS, and LSG characters, and no significant differences between hybrids and either maternal (ILS, FP) or paternal (PV) progenitors.
12. Three inferred representatives of A. neomexicana (AMNH R-138881, R-151740 from Conchas Lake and R-151741 from Fort Sumner) had diploid karyotypes comprising one normal tigris group haploid complement and one normal sexlineata group haploid complement of chromosomes, or 2n = 46, consistent with their species identification.
13 The five A. sexlineata viridis examined had the normal sexlineata group karyotypes, with each lizard having one distinctive subtelocentric pair of Set II chromosomes (about the fourth largest pair) instead of two pairs as previously reported.
14. A suspected hybrid male (AMNH R-151739) from Conchas Lake was a triploid having 3n = 69 chromosomes, comprising the full diploid karyotype of A. neomexicana and a second haploid complement of sexlineata group chromosomes.
15. Although A. neomexicana and A. tesselata have indistinguishable karyotypes based on one chromosome complement from each of the tigris and sexlineata species groups, no hybrids of the dissimilar-sized A. tesselata and A. sexlineata viridis were discovered at Conchas Lake in syntopic assemblages of these species at sites CL-5* and CL-2*.
16. The two A. neomexicana analyzed from Conchas Lake and Fort Sumner had the same protein genotypes at each of 23 loci, except for one allele in the lizard from Fort Sumner.
17. Twelve or 13 loci (52–56%) in both specimens of A. neomexicana had alleles in the heterozygous state, attesting to the ultimate origin of this taxon from a hybridization event (A. tigris marmorata ♀ × A. inornata ♂).
18. The specimen of A. neomexicana from Fort Sumner differed from the one from Conchas Lake only by possessing one b-allele at sMDH (heterozygous ab).
19. The specimen from Conchas Lake seemed to be identical at all loci and all alleles to specimens of the most common and most widely distributed clone of A. neomexicana from elsewhere in its geographic range, whereas the specimen from Fort Sumner might be allied with the sMDH allelle known to occur infrequently in A. neomexicana in the vicinity of Engle, Sierra County, New Mexico.
20. Typically, A. neomexicana and A. tesselata (including those from Conchas Lake) differ at 10 protein loci among those examined for this report: sMDH, sMDHP, sIDH, ESTD, PEPA, PEPB, ADA, MPI, GPI, and PGM2. The new specimens we examined for the present report that appeared to be A. neomexicana are correctly identified as such, based on these loci, not a new clone of A. tesselata.
Acknowledgments
The specimens listed in appendices 1–8 using AMNH, and UADZ numbers were collected under provisions of yearly permits granted to GJM, CJC, James E. Cordes, and JMW by the New Mexico Department of Game and Fish. We gratefully acknowledge the assistance of the following individuals in the collection of Aspidoscelis at Conchas Lake: James E. Cordes, Jeffery Briggler, James M. Walker, Jr., Glenn K. Manning, and Carol R. Townsend. The AMNH specimens of Aspidoscelis sexlineata from Colorado, Texas, and Georgia listed in appendix 8 were collected by CJC, Jeffrey A. Cole, Carol R. Townsend, and Richard G. Zweifel under permits issued by Colorado Division of Wildlife, Texas Parks and Wildlife, and Georgia Wildlife Resources Division, respectively. Assistance in obtaining lizards at Fort Sumner was provided by Chad E. Montgomery and Justin Hobart. Christopher Raxworthy and Linda Ford provided curatorial services for and loans of AMNH specimens utilized in this study. Much of the work by CJC was conducted at the Southwestern Research Station while it was directed by Wade C. Sherbrooke (current Director, Dawn S. Wilson). Color photographs A and B of figure 9 and assistance with laboratory work were provided by Carol R. Townsend. Finally and most importantly, without information provided by Beth E. Leuck (personal commun.) in 1988–1990 pertaining to A. neomexicana at Conchas Lake there would have been no preliminary findings on the species by JMW to set the stage for the current study. Moreover, her critical review of this manuscript materially improved it.
REFERENCES
Appendices
APPENDIX 1
Specimens of Aspidoscelis examined from Conchas Lake, site CL-1* (South of Clabberhill Ranch), 0.5 km S of gate, and an area 0.4 km NW (north of North Area Recreation Area), 1259 m, San Miguel County, New Mexico, collected by B.E. Leuck and associates (1978), GJM and J.T. Briggler (2001), and GJM (2003). Abbreviations: A.n. (= A. neomexicana ♀♀); A.s. (= A. sexlineata viridis ♀♂); A.h. (= hybrid A. neomexicana × A. sexlineata viridis ♀♂); A.e. (= A. exsanguis ♀♀); A.t. C (= A. tesselata pattern class C ♀♀).
22 July 1978: A.n. (LACM 128281, not examined, N = 1); A.h. (OMNH 35109♀, N = 1).
21 June 2000: A.s. (2 observed by GJM).
9 June 2001: A.n. (UADZ 7388, 7390, N = 2); A.e. (UADZ 7389, N = 1).
21 August 2001: A.n. (UADZ 7528–7537, 7539, 7541, N = 12); A.e. (UADZ 7540, N = 1); A.t. C (UADZ 7538, N = 1).
14 August 2003: A.t. C (UADZ 7705, N = 1).
APPENDIX 2
Specimens of Aspidoscelis examined from Conchas Lake, site CL-13 (Cove Campground), North Area Recreation Area, Cove Campground, 1245 m, San Miguel County, New Mexico, collected by GJM (2000—2002). Abbreviations: A.n. (= A. neomexicana ♀♀); A.t. C (= A. tesselata pattern class C ♀♀); k = source of karyotype; p = source of protein electrophoresis.
APPENDIX 3
Specimens of Aspidoscelis examined from Conchas Lake, site CL-4 (North of Canadian River), north side of Conchas Dam below picnic area overlooking Canadian River, 1120–1243 m, San Miguel County, New Mexico, collected by JMW and associates (1988, 1989, 1997, 2000) and GJM and JMW (2000, 2001). Abbreviations: A.n. (= A. neomexicana ♀♀); A.e. (= A. exsanguis ♀♀); A.t. C (= A. tesselata pattern class C ♀♀).
12 August 1988: A.e. (UADZ 3434, N = 1); A.t. C (UADZ 3446, N = 1).
3 August 1989: A.n. (UADZ 3741—3743, N = 3); A.t. C (UADZ 3744–3749, N = 6).
7 June 1990: A.n. (UADZ 4175–4176, N = 2); A.e. (UADZ 4171—4174, N = 4); A.t. C (UADZ 4158—4170, N = 13).
15 July 1997: A.n. (UADZ 5986—5988, N = 4); A.t. C (UADZ 5990, 5991, N = 2).
12 June 2000: A.n. (UADZ 7317–7319, N = 3); A.e. (UADZ 7320–7325, N = 6); A.t. C (UADZ 7326–7328, N = 3).
15 June 2000: A.e. (UADZ 7334, N = 1).
6 June 2001: A.t. C (UADZ 7370–7373, N = 4).
17 August 2001: A.n. (UADZ 7462, N = 1).
APPENDIX 4
Specimens of Aspidoscelis examined from Conchas Lake, site CL-5* (East of Conchas Lake Levee), listed by habitat component in the vicinity of 2—3 km S Conchas Dam, or east of the south end of the levee, along New Mexico Hwy. 129, 1258—1274 m, San Miguel County, New Mexico, collected by JMW and J.E. Cordes (1988, 1989) and GJM and J.T. Briggler (2000—2002). Abbreviations: A.n. (= A. neomexicana ♀♀); A.s. (A. sexlineata viridis ♀♂); A.h. (= hybrid A. neomexicana × A. sexlineata viridis ♀♂); A.t. C or D (= A. tesselata pattern classes C or D ♀♀).
Valley-plateau-hill component (CL-5VPH*).a
12 July 1988: A.n. (UADZ 3235 = AMNH 146599, N = 1); A.s. (UADZ 3248—3269, 3270 = AMNH 146600, 3271, 3273—3275, N = 26); A.h. (UADZ 3272 = AMNH 144085♂, N = 1); A.t. C (UADZ 3214–3215, 3217— 3224, 3226–3227, 3229, 3231—3237, 3239— 3241, 3243, 3245—3247, N = 27); A.t. D (UADZ 3216, 3225, 3228, 3230, 3238, 3242, 3244, N = 7).
12 August 1988: A.s. (UADZ 3445, N = 1); A.t. C (UADZ 3432, 433, 3435, 3437—3439, 3442—3444, 3448–3449, N = 11); A.t. D (UADZ 3436, 3440–3441, 3450, N = 4).
13 June 2000: A.t. C (UADZ 7329–7330, N = 2).
11 June 2001: A.s. (UADZ 7405, N = 1); A.t. C (UADZ 7404, 7406, N = 2); A.t. D (UADZ 7407, N = 1).
18 August 2001: A.n. (UADZ 7464, 7466, 7469, N = 3); A.s. (UADZ 7470, 7476, N = 2); A.t. C (UADZ 7465, 7467–7468, 7471–7475, N = 8); A.t. D (UADZ 7477, N = 1).
21 August 2001: A.s. (UADZ 7527, N = 1).
8 June 2002: A.n. (UADZ 7576–7577, N = 2); A.t. C (UADZ 7571–7575, N = 5).
Valley component (CL-5V) 14 June 2000: A.s. (UADZ 7331, N = 1); A.t. C (UADZ 7332, N = 1).
8 June 2001: A.s. (UADZ 7381–7382, N = 2); A.t. C (UADZ 7380, N = 1).
10 June 2001: A.n. (UADZ 7398, N = 1); A.s. (UADZ 7391–7396, 7399, 7401–7402, N = 9); A.t. C (UADZ 7397, 7400, 7403, N = 3).
17 August 2001: A.s. (UADZ 7463, N = 1).
9 June 2002: A.n. (UADZ 7581, N = 1); A.s. (UADZ 7578–7579, 7582, 7584, N = 4); A.t. D (UADZ 7580, 7583, N = 2).
aAll UADZ specimens were collected in the valley except 4 from the top of the hill (A.t. C [UADZ 3214, 3435] and A.t. D [UADZ 3230, 3436]) and 12 from the plateau (A.t. C [UADZ 3218, 3241, 3243, 3449]; A.t. D [UADZ 3228, 3244]; A.s. [UADZ 3258, 3264, 3266, 3267, 3271]; and A.h. [UADZ 3272]).
APPENDIX 5
Specimens of Aspidoscelis examined from Conchas Lake, site CL-2* (South Recreation Area) listed by habitat components, 1279—1310 m, San Miguel County, New Mexico, collected by CJC and C.R. Townsend (1976, 1978, 1981, 1990) and GJM and J. T. Briggler (2000—2002). Abbreviations: A.n. (= A. neomexicana ♀♀); A.s. (A. sexlineata viridis ♀♂); A.h. (= hybrid A. neomexicana × A. sexlineata viridis ♀♂); A.e. (= A. exsanguis ♀♀); A.t. C or D (= A. tesselata pattern class C or D ♀♀); k = source of karyotype; p = source of protein electrophoresis.
South Campground component (CL-2C*).
22–23 May 1976: A.s. (AMNH R-114231, k, p, R-114232, R-114233—R-114235, k, p, R-122828–R-122829, N = 7); A.t. C (AMNH R-123029, R-123033, N = 2); A.t. D (AMNH R-114236–R-114237, R-123047—R-123049, N = 5).
28 May 1978: A.t. C (AMNH R-119545, N = 1).
28–29 May 1978: A.t. C (AMNH R-123025, R-123050–R-123051, N = 3); A.t. D (AMNH R-119545, R-123037, R-123042, R-123052, N = 4).
29 May 1978: A.s. (AMNH R-119534, N = 1).
19 July 1981: A.s. (AMNH R-135193—R-135196, R-122830, R-123053, k, p, N = 6).
28 May 1990: A.n. (AMNH R-136881, k, p, N = 1); A.t. C (AMNH R-136875—R-136879, N = 5); A.t. D (AMNH R-136880, N = 1).
19 June 2000: A.n. (UADZ 7347, N = 1); A.s. (UADZ 7346, 7348, N = 2); A.h. (UADZ 7349♀, N = 1); A.t. C (UADZ 7345, N = 1).
6 June 2001: A.n. (UADZ 7374, N = 1); A.s. (UADZ 7375, N = 1).
17 August 2001: A.n. (UADZ 7456–7459, 7461, N = 5); A.s. (UADZ 7460, N = 1); A.h. (UADZ 7455♀, N = 1).
6 June 2002: A.e. (UADZ 7558–7559, N = 2); A.t. D (UADZ 7557, N = 1).
13 August 2003: A.n. (UADZ 7690–7691, 7694, 7699, 7702–7704, N = 7); A.s. (UADZ 7692, 7695, N = 2); A.h. (UADZ 7700♂, N = 1); A.t. C (UADZ 7696, N = 1); A.t. D (UADZ 7693, N = 1).
Group Shelter component (CL-2G)
23 June 2000: A.n. (UADZ 7369, N = 1).
8 June 2001: A.s. (UADZ 7379, N = 1).
6 June 2002: A.e. (UADZ 7560, N = 1).
Hill component (CL-2H*)
19 June 2000: A.s. (UADZ 7343, N = 1); A.h. (UADZ 7344♂, N = 1).
17 August 2001: A.n. (UADZ 7449–7451, 7453– 7454, N = 5); A.h. (UADZ 7448♂, 7452♀, N = 2).
6 June 2002: A.h. (UADZ 7553♂, 7554♀, 7555♀, 7556♀, N = 4).
13 August 2003: A.n. (UADZ 7689, 7697–7698, 7701, N = 4).
Juniper Campground component (CL-2J*)
14 June 2001: A.n. (UADZ 7442, N = 1); A.s. (UADZ 7443, N = 1).
7 June 2002: A.n. (UADZ 7562–7563, 7565– 7568, N = 6); A.h. (UADZ 7561♂, 7570♂ = AMNH 151739, k, p, N = 2); A.t. C (UADZ 7564, N = 1); A.t. D (UADZ 7569, N = 1).
12 August 2003: A.n. (UADZ 7672–7673, 7678– 7688, N = 13); A.s. (UADZ 7674, N = 1); A.t. C (UADZ 7670–7671, 7675–7677, N = 5).
Lodge component (CL-2L*)
15 June 2000: A.n. (UADZ 7446, N = 1); A.s. (UADZ 7444, 7447, N = 2); A.h. (UADZ 7445♀, N = 1).
18 August 2001: A.n. (UADZ 7479–7480, N = 2); A.t. C (UADZ 7478, N = 1).
20 August 2001: A.n. (UADZ 7523, N = 1); A.e. (UADZ 7525, N = 1); A.t. D (UADZ 7524, N = 1).
8 August 2003: A.t. C (UADZ 7669, N = 1).
APPENDIX 6
APPENDIX 7
Specimens of Aspidoscelis examined from Fort Sumner, site FS-2 (Fort Sumner–Railroad Depot), De Baca County, New Mexico, collected by GJM in 2002. Abbreviations: A.n. (= A. neomexicana ♀♀); A.s. (= A. sexlineata viridis ♀♂); A.t. E (= A. tesselata pattern class E ♀♀); k = source of karyotype; p = source of protein electrophoresis.
APPENDIX 8
Specimens of Aspidoscelis listed here were collected in states other than New Mexico and used in comparisons of photographs, karyotypes, and proteins.
Aspidoscelis sexlineata viridis: COLORADO: Kiowa County; 15.0 km N of Eads at Rush Creek (AMNH R-108142, photograph and karyotype). Pueblo County; Huerfano River bridge on Doyle Road, 29.8 km (by road) south of Avondale (AMNH R-13112, proteins). TEXAS: Brooks County; 11.4 km (by U.S. Hwy 281) south of Falfurrias (AMNH R-126893–R-126898 and R-126901–R-126902, proteins).
Aspidoscelis sexlineata sexlineata: GEORGIA: Liberty County; St. Catherines Island (AMNH R-119487, R-119489–R-119493, and R-120233–R-120236, proteins). Chatham County; Ossabaw Island (AMNH R-119498–R-119499, karyotypes and proteins).
Fig. 1.
Map from Maptech (vers. 5.03. 2001. Amesbury, MD) showing distribution of study sites for Aspidoscelis at Conchas Lake, San Miguel County, New Mexico: South of Clabberhill Ranch (CL-1* = 1), Cove Campground (CL-13 = 13), North of Canadian River (CL-4 = 4), East of Conchas Lake Levee (CL-5* = 5), and South Recreation Area (CL-2* = 2). Hybrids of A. neomexicana × A. sexlineata viridis have been collected at sites numbered from north to south 1, 5, and 2 in order of their discovery
Fig. 2.
Habitats located north of the Canadian River and east of Conchas Lake, San Miguel County, New Mexico. Top. Looking north–northwest at the transition from relatively stable mesquite-grassland (foreground) to juniper-dotted hills (background) at South of Clabberhill Ranch (CL-1*) from which individuals of Aspidoscelis neomexicana, A. tesselata C, A. exsanguis, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis have been collected. Bottom. Looking south-southwest at degraded mesquite-grassland at Cove Campground (CL-13) from which individuals of Aspidoscelis neomexicana (including AMNH R-151740 used in karyotypic and electrophoretic analyses in this study) and A. tesselata C have been collected
Fig. 3.
A relatively stable topographically and ecologically complex area located north of the Canadian River and east of Conchas Lake Dam as viewed from the south side of the river, San Miguel County, New Mexico. North of Canadian River (CL-4); V near middle shows the area with open-structured mesquite, grasses-weeds, and junipers along an unpaved road on the upper bench near a precipice from which individuals of Aspidoscelis neomexicana, A. tesselata C, and A. exsanguis, but not A. sexlineata viridis or A. tesselata D, have been collected; lower V shows bench near the river with dense mesquite, grasses, and weeds in which only individuals of A. neomexicana have been observed. The presence of Aspidoscelis neomexicana along the rocky precipice at CL-4, from which it flees into the boulders below when threatened, makes this site the most unusual known to us for the species throughout its range
Fig. 4.
Habitats found south of the Canadian River at East of Conchas Lake Levee (CL-5*), San Miguel County, New Mexico. Top. Looking north–northwest at relatively stable mesquite-grassland at the Valley Component (CL-5V) from which individuals of Aspidoscelis neomexicana, A. tesselata C and D, and A. sexlineata viridis have been collected (A. exsanguis was not observed at either component at this site from 1988 to 2002). Bottom. Looking south–southwest at the topographically and ecologically complex (foreground to background) Valley-plateau-hill Component (CL-5VPH*) from which individuals of Aspidoscelis neomexicana, A. tesselata C and D, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis have been collected
Fig. 5.
Habitats modified by the activities of man south of Conchas Lake in South Recreation Area (CL-2*), San Miguel County, New Mexico. Top. Looking east at fragmented grass-weed associations along and among boulders and trees at the South Campground Component (CL-2C*) from which individuals of Aspidoscelis neomexicana, A. tesselata C and D, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis have been collected. Bottom. A south–southeast view of the mesquite-grass-weed association at the Hill Component (CL2H*) from which individuals of Aspidoscelis neomexicana, A. tesselata D, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis have been collected
Fig. 6.
An example of extreme habitat degradation resulting from the activities of man south of Conchas Lake in South Recreation Area (CL-2*), San Miguel County, New Mexico. Looking northeast across the Juniper Campground Component (CL-2J*) from which individuals of Aspidoscelis neomexicana, A. tesselata C and D, A. exsanguis, A. sexlineata viridis, and A. neomexicana × A. sexlineata viridis (including AMNH R-151739 used in karyotypic and electrophoretic analyses in this study) have been collected
Fig. 7.
Habitats at Fort Sumner, De Baca County, New Mexico, inhabited by Aspidoscelis lizards. Top. Looking north along a roadside (cedar trees on the left form the border of a cemetery) with a grass-weed association (left of fence row) near the Fort Sumner–De Baca County Landfill (FS-1) from which individuals of Aspidoscelis neomexicana, A. tesselata E, and A. sexlineata viridis have been collected. Bottom. Looking south, near view of a patch of mesquite-grassland habitat at Fort Sumner– Railroad Depot (FS-2) from which individuals of Aspidoscelis neomexicana (including AMNH R-151741 used in karyotypic and electrophoretic analyses in this study), A. tesselata E, and A. sexlineata viridis have been collected
Fig. 8.
Four or five generations represented by specimens of Aspidoscelis neomexicana × A. sexlineata viridis from South Recreation Area (CL-2*), Conchas Lake, San Miguel County, New Mexico, inferred from date of collection and snout–vent length (mm). Some lizards are active at the site from May to October (MJJASO) each year; horizontal line representing each lizard extends from the inferred year and month of hatching to the actual year and month of collection (> = younger or older age uncertain)
Fig. 9.
Life colors in three lizards used in genetic studies. A. Diploid Aspidoscelis neomexicana adult female, AMNH R-151740, SVL 72 mm, Cove Campground (CL-13), Conchas Lake, San Miguel County, New Mexico. B. Triploid Aspidoscelis neomexicana × A. sexlineata viridis hybrid male, AMNH R-151739, SVL 74 mm, from South Recreation Area (CL-2*), Conchas Lake, San Miguel County, New Mexico. C. Diploid A. sexlineata viridis adult male, AMNH R-108142, SVL 69 mm, from Kiowa County, Colorado
Fig. 10.
Unusual dorsal pattern in OMNH 35109, a putative hybrid female, SVL 69 mm, of Aspidoscelis neomexicana × A. sexlineata viridis from South of Clabberhill Ranch (CL-1*), Conchas Lake, San Miguel County, New Mexico
Fig. 11.
Adult specimens of Aspidoscelis neomexicana of special significance. A. AMNH R-151740 ♀, SVL 73 mm, from Cove Campground (CL-13), Conchas Lake, San Miguel County, New Mexico, used in karyotypic and electrophoretic analyses in this study. B. MSB 65617 ♀, SVL 79 mm, from Fort Sumner–De Baca County Landfill (FS-1), Fort Sumner, De Baca County, New Mexico; first reported specimen of the species from the county (Taylor, 2002). C. AMNH R-151741 ♀, SVL 73 mm, from Fort Sumner–Railroad Depot (FS-2), Fort Sumner, De Baca County, New Mexico, used in karyotypic and electrophoretic analyses in this study
Fig. 12.
Adult Aspidoscelis neomexicana × A. sexlineata viridis hybrids from components of the South Recreation Area (CL-2*), Conchas Lake, San Miguel County, New Mexico. A. AMNH R-151739 ♂, CL-2J*, SVL 74 mm. B. UADZ 7445 ♀, CL-2L*, SVL 69 mm. C. UADZ 7553 ♂, CL-2H*, SVL 72 mm. D. UADZ 7554 ♀, CL-2H*, SVL 79 mm. E. UADZ 7344 ♂, CL-2H*, SVL 61 mm. F. UADZ 7349 ♀, CL-2C*, SVL 64 mm
Fig. 13.
Subadult Aspidoscelis neomexicana × A. sexlineata viridis hybrids from components of the South Recreation Area (CL-2*), Conchas Lake, San Miguel County, New Mexico. A. UADZ 7561 ♂, CL-2J*, SVL 49 mm. B. UADZ 7556 ♀, CL-2H*, SVL 49 mm. C. UADZ 7555 ♀, CL-2H*, SVL 47 mm. D. UADZ 7452 ♂, CL-2H*, SVL 37 mm. E. UADZ 7448 ♂, CL-2H*, SVL 45 mm. F. UADZ 7455 ♀, CL-2C*, SVL 48 mm
Fig. 14.
Comparison of mesoptychial scale size in parental forms and their hybrids. A. UADZ 7318 ♀, SVL 80 mm, small scales in Aspidoscelis neomexicana. B. UADZ 7464 ♀, SVL 68 mm, small scales in A. neomexicana. C. UADZ 7396 ♀, SVL 63 mm, greatly enlarged scales in A. sexlineata viridis. D. UADZ 7553 ♂, SVL 72 mm, enlarged scales in A. neomexicana × A. sexlineata viridis. E. UADZ 7554 ♀, SVL 79 mm, enlarged scales in A. neomexicana × A. sexlineata viridis
Fig. 15.
Pattern of morphological variation expressed by the distribution of scores on the first two principal components extracted from a correlation matrix of eight meristic characters for 49 A. neomexicana (⋄), 26 A. sexlineata viridis (▪ = ♂ and □ = ♀), 13 A. neomexicana × A. sexlineata viridis (• = ♂ and ○ = ♀), AMNH 144085 = UADZ 3272 (×, assigned to the hybrid group as indicated by Walker et al., 1990), OMNH 35109 (+, assigned to the hybrid group as suspected by B.E. Leuck), and 26 A. tesselata C (▵) from Conchas Lake, San Miguel County, New Mexico. Ellipses represent the 95% confidence limits of each group
Fig. 16.
Pattern of morphological distinctiveness expressed by the distribution of canonical variate scores derived from a linear canonical variate analysis of eight meristic characters in 49 A. neomexicana (⋄), 26 A. sexlineata viridis (▪ = ♂ and □ = ♀), 13 A. neomexicana × A. sexlineata viridis (• = ♂ and ○ = ♀), AMNH 144085 = UADZ 3272 (×, assigned to the hybrid group as indicated by Walker et al., 1990), OMNH 35109 (+, assigned to the hybrid group as suspected by B.E. Leuck), and 26 A. tesselata C (▵) from Conchas Lake, San Miguel County, New Mexico. Ellipses represent the 95% confidence limits of each group
Fig. 17.
Karyotype of a triploid whiptail lizard (AMNH R-151739; 3n = 69) from Conchas Lake, San Miguel County, New Mexico. This is a hybrid between A. neomexicana × A. sexlineata viridis. The three haploid genomes (two rows of chromosomes each) are arranged to illustrate ancestry of the hybrid, as follows: A. tigris marmorata (top) × A. inornata (middle), which were inherited from the diploid maternal parent of the hybrid (A. neomexicana), and A. sexlineata viridis (bottom), from the paternal parent. Bar = 10 μm
Fig. 18.
Electrophoretic phenotypes of five proteins as expressed on separate gels. PEPA, a dimeric enzyme, for three lizards. LDH1, a tetrameric enzyme, for three lizards. ESTD, a dimeric enzyme, for three lizards. sMDH, a dimeric enzyme, for four lizards. TF, a monomeric enzyme, for six lizards; white dots mark the three isozymes from the hybrid. Letters below gel identify allozymes based on alleles present (table 13). Lanes for individual lizards are labeled beside the gel (with genotype) as follows: I, A. inornata; M, A. tigris marmorata; N, A. neomexicana; NC, A. neomexicana from Conchas Lake; NF, A. neomexicana from Fort Sumner; N × S, the hybrid; S, A. sexlineata viridis. Anode is to the right, ˆ indicates relative position of sample applications
TABLE 1
Study Sites and Their Components, Date of Discovery and Discoverers of Aspidoscelis neomexicana, and Species of Aspidoscelis Known to Occur at Each Site Listed in Order of Their Inferred Abundance Based on Collecting Records
TABLE 2
Computer-Generated Straight-Line Distances in Kilometers Between Aspidoscelis Study Sites and Their Ecological Components at Conchas Lake, San Miguel County, New Mexico
TABLE 3
Aspidoscelis Lizards Observed and Collected at Conchas Lake in an Area of No Contact Between Parthenogens and A. sexlineata viridis, CL-4 (North of Canadian River), North Side of Conchas Dam Below Picnic Area Overlooking Canadian River, 1220–1243 m, San Miguel County, New Mexico, by JMW and Associates (1988–1990, 1997) and GJM, JMW, and J.T. Briggler (2000–2001)
TABLE 4
Aspidoscelis Lizards Observed and Collected at Conchas Lake, CL-5* (East of Conchas Lake Levee), at Both Ecological Components in the Vicinity of 2–3 km South of Conchas Dam, or East of the South End of the Levee, Along New Mexico Highway 129, 1258–1274 m, San Miguel County, New Mexico, by JMW and J.E. Cordes (1988) and GJM and J.T. Briggler (2000–2002)
TABLE 5
Aspidoscelis Lizards Observed and Collected at Conchas Lake, CL-2* (South Recreation Area), at All Ecological Components in and Near the South Recreation Area, 1279–1310 m, San Miguel County, New Mexico, by CJC and C.R. Townsend (1976, 1978, 1981, 1990) and GJM and J.T. Briggler (2000–2003)
TABLE 6
Comparison of Five Aspects of Natural History Pertaining to Four Examples of Hybridization Between Parthenogenetic and Gonochoristic Species of Aspidoscelis in New Mexico
TABLE 7
Variation in Three Characters of Scutellation in Aspidoscelis neomexicana from sites CL-1*, CL-13, CL-4, CL-5*, and CL-2*, A. neomexicana × A. sexlineata viridis (= hybrids) from CL-5* and CL-2*, and A. sexlineata viridis from CL-5* and CL-2* at Conchas Lake, San Miguel County, New Mexico
TABLE 8
Comparisons of Coefficients of Variation in Three Sets of Parental Species and their Hybrids (genus Aspidoscelis) from Sites in New Mexico (Data for set 1 from this Study, each SD and COV for set 2 calculated from Taylor and Walker [1996], COV for set 3 calculated from Taylor et al. [2001])
TABLE 9
Comparisons of Pooled Samples of Aspidoscelis neomexicana (A.n., sites CL-1*, CL-13, CL-4, CL-5*, CL-2*), A. neomexicana × A. sexlineata viridis (A.h., sites CL-5*, CL-2*), and A. sexlineata viridis (A.s., sites CL-5*, CL-2*) from Conchas Lake, San Miguel County, New Mexico
TABLE 9
(Continued)
TABLE 10
Data (mean ± SE, Range) for Eight Characters of Scutellation and a Ratio in Samples of Aspidoscelis neomexicana, A. sexlineata viridis, and A. tesselata C Compared to Data for Hydrids of A. neomexicana × A. sexlineata viridis from Sites at Conchas Lake, San Miguel County, New Mexico
TABLE 10
(Continued)
TABLE 11
Factor Loadings for Two Principal Components and Two Canonical Variates Derived from Meristic Variation Among Individuals of Aspidoscelis neomexicana, A. sexlineata viridis, A. tesselata C, and A. neomexicana × A. sexlineata viridis from Conchas Lake, San Miguel County, New Mexico
TABLE 12
Mean Mahalanobis Distances (D2) Among Centroids of Four a priori Groups Compared with the Number of Haploid Genomes Shared Between Pairs of a priori Groups Used in a CV Analysis
TABLE 13
Genotypes or Allelesa at 23 Gene Locib in Samples of Aspidoscelis neomexicana, A. neomexicana × A. sexlineata viridis, and A. sexlineata viridis
TABLE 14
Evaluation of the Hypothesis of a Human Introduction for Aspidoscelis neomexicana at Conchas Lake, San Miguel County, New Mexico
