Literature Review

Kirsch (1870: 369) established the genus Aphelocerus on the basis of A. sturnus (Kirsch, 1870: 370) which he placed in subfamily Tillinae, a practice followed by Lodhe (1900: 23), Schenkling (1903: 24, 1910: 26), Blackwelder (1945: 382), Corporaal (1950: 56), and Winkler (1961: 39). Before Kirsch, Chevrolat (1843: 25) described nitidus under the clerine genus Clerus and in 1874 he described leucomelas, to which he assigned the tilline genus Tillus. Additional species of Aphelocerus were described under Clerus by Chevrolat (1874: 296), Spinola (1844: 238), and Gorham (1882: 162).

After examining the type specimen of A. sturnus Kirsch, Barr (1976: 18) correctly reassigned Aphelocerus to the subfamily Clerinae, where it became a senior synonym (Barr, 1976: 18) of Wolcott's Adelphoclerus (Wolcott, 1910: 356; 1927: 73; Ekis, 1975: 27). Rifkind (1995: 19) briefly discussed two members of this genus in his faunal work of Belize Cleridae.

MATERIALS AND METHODS

This study is based on more than 1000 adult specimens borrowed from museum and private collections, or collected by me during fieldwork. I observed living aphelocerans in Mexico, Guatemala, Nicaragua, Costa Rica, and Panama. Live specimens of these checkered beetles were placed in killing jars with cyanide or ethyl acetate, then immersed in Pampel's to facilitate investigations of internal anatomy. Investigations of the digestive system organs and those of the internal reproductive system continue to produce variations useful particularly for studies of supraspecific systematics.

During the initial stages of the classificatory process, I first sorted specimens according to geographic origin, and then severed the abdomen from all male specimens to determine the extent of structural variation of the pygidium and aedeagus. Abdomens were easily separated from pinned beetles, but point-mounted specimens had to be relaxed in a warm soapy water solution, and then dissected under water. In time, I devised a more efficient method of gaining access to the genitalia of dry, point-mounted specimens as follows: Abdomens were severed from dry specimens by first removing the pin from the paper point, then the beetles, while still attached to the paper point, were placed upside down onto an inverted pinning tray matted with very soft tissue paper. Next, a number three pin was used to dislodge the abdomen from the thorax by piercing the abdomen behind/beneath each metacoxa. Some specimens were soaked and cleaned with a sonic cleaner, then dried and repinned. Severed abdomens were then subjected to a solution of warm KOH that facilitated the extraction of the aedeagus, ovipositor, and pygidium. The best results were obtained when the dry abdomens were immersed overnight in a 25% cold solution of KOH. Female abdomens were similarly treated when the pygidium and/or sixth visible abdominal sternum showed noteworthy variations.

Techniques of illustration and measurements were similar to those I described in my works of Perilypus (Ekis, 1977: 6) and Plocamocera (Opitz, 2004: 7). Within descriptions there are numbers in parentheses separated by a colon. These numbers represent measurements intended to provide dimensional ratios between structures that are being compared. Standard anatomical terminology used in this work originates from Nichols (1989). I recognize that the plate that constitutes the visible venter of each abdominal segment in beetles represents a portion of the “real” segmental sternum. As Snodgrass (1935: 78) indicates, “… in the abdomen the sternal plates appear to contain, in most cases the entire basal parts of the otherwise suppressed limbs.” However, I prefer to follow convention by using the term “sternum” to indicate that portion of sclerotization one sees in the checkered beetle adult abdominal segment. The figures of the reproductive organs show one of two ovaries, one of two testes, and one of two pairs of male accessory glands. The short transverse lines in the Character-Matrix Table (table 1) denote that a particular character state was not observed in a species group.

The excellent work of Rolland W. Brown (1966) was very helpful in the selection of specific epithets. The locality label information associated with each holotype specimen is presented in the species descriptions sequentially and precisely in the form that such information is written on the pinned specimen labels that are attached on the holotype specimen. In the “Paratypes” section of each new species description I have followed a sequence of recording locality information as follows: Country: State, Province, or Department: Specific locality. When more than one field collection was made from the same local locality, and the collections differ only in date, I separated the collection dates by a semicolon. Different localities within the same state, province, or departments were also separated by a semicolon. Different states, provinces, or departments, within the same country were separated by a colon. I examined the primary type of all nominal species included in this study.

The members of Aphelocerus and all New World genera with a well-developed basal denticle on the tarsal claws, such as Caestron, Placopterus, and Enoclerus, have a particularly long seta near the apex of the elytra. I have ascertained that this is a synapomorphic characteristic that links the aforementioned genera evolutionarily. I have named this extraordinarily long seta a “trich”. As no bothrium was noted at the base of this seta, it cannot be termed a trichobothrium.

Assessment of Species-Level Discontinuities

The species concept applied in this contribution is based on fundamentals established by Ernst Mayr (1969). As behavioral or other biologic evidence of reproductive isolation was unavailable, I relied on anatomical differences and geographic parameters to infer species status. In the absence of evidence to the contrary, specimens from allopatric populations with similar genitalic characteristics were considered conspecific. Conversely, beetles from sympatric populations with varying genitalic characteristics were considered separate species. I found the presence or absence and distribution of secondary degree (2°) elytral setae valuable for predicting conspecificity or nonconspecificity in conjunction with variations of genitalia characteristics. Secondary degree setae are shorter and more decumbent than primary setae (see fig. 260). The secondary setae are organized into a midelytral tuft in most of the species. The shape of the tuft, whether it is comprised of one or two variously developed setal patches, and orientation of the setae in each patch are also useful for discriminating species. The setal tuft must be viewed at different angles (by tilting the specimen) to allow light reflections to bring out the true shape of the setal patches and the orientation of the setae in each patch. In some species the two, or three, setal patches are contiguous and as such may be interpreted as forming a single patch. However, in these cases, the direction of the setae in each patch will differ to establish whether a tuft is comprised of one, two, or three patches. Many species of the yungas species group are superficially similar such that preparation of the diagnostic key was very difficult. Interspecific differences of phylogenetic use were particularly scarce. Inconvenient characteristics, such as body size, had to be used on occasion to complete a diagnostic couplet. To facilitate the process of identifying species more, I provide illustrations of the elytral discal setal tuft of several species (for example, see figs. 165–183). The 66 nominal species presented in this work represent my assessment of the magnitude of anatomic and geographic divergence that represents reproductive isolation in the genus Aphelocerus.

In my systematic projects with checkered beetles, I have found it necessary to examine type specimens that date to the 1800s. At times, there was doubt as to the authenticity of a specimen being the primary type, mainly due to discrepancies between pinned label information and information in published descriptions. Therefore, at the beginning of each species description I document the exact sequence of labels on the holotype or lectotype.

Phylogenetic Methods

The phylogenetic hypotheses presented herein are based on principles advocated by Willi Hennig (1966). Elsewhere, I have discussed these principles in detail (Ekis, 1977: 116; Opitz, 2004: 9). Character states were assessed as apomorphic or plesiomorphic on the basis of out-group comparisons, and the data matrix was analyzed with Hennig 86 version 1.5 (Farris, 1988).

Repositories of Specimens

The following abbreviations indicate collections from which specimens were borrowed, and were taken from Arnett, et al. (1993). My sincere thanks to the curators of these collections acknowledged in parentheses.

Mimetic Associations

Any naturalist who has collected beetles extensively in the Neotropics will attest to the abundance of resemblances of color patterns and/or body shapes across familial lines. Such similarities among phylogenetically “unrelated” species are difficult to interpret as chance occurrences. They are often very fine tuned phenotypic similarities and invite the speculation that they represent some kind of adaptive convergence. The concept of mimicry, although not easily proven, is often a logical explanation for such convergences among distantly related species. However, as acknowledged by Hespenheide (1995: 146), “most cases of mimicry cannot be subjected to experimental verification because of the rarity of the putative mimics and the difficulty in designing an experimental protocol that would realistically test a given case”… of mimicry.

Integumental color, patterns of white setae on various parts of the integument, and body facies strongly suggest that species of Aphelocerus are involved in a mimetic complex. I do not believe that the basis of this mimicry is distastefulness, but rather that it is based on such factors as escape behavior or morphological resemblance to aggressive models such as ants. It is my contention that Aphelocerus species are involved in a mimetic complex, probably Mullerian, that includes species of Buprestidae, Cerambycidae, Chrysomelidae, Curculionidae, Formicidae, and spiders.

I observed live A. myrmecoides, n.sp., among Myrmex weevils moving on broadleaf herbaceous hedge growth. The similarity between these particular clerids and the weevils is very profound in general form (compare figs. 163, 164) and in such anatomical details as the presence of white setal tufts on the sides of the body. Their locomotory differences, however, betray their identity with the clerid having a rapid scurrying movement and the weevil a slow, more deliberate gait. At present, one can only speculate about the functional basis of this suspected Mullerian complex. However, the extraordinary development of the antenna and legs among some of these beetles suggests a Batesian mimicry involving ants or perhaps spiders.

Members of the myrmecoides species group have an oval, short hind body and highly convex elytra that could reflect an adaptation towards the cephalothorax and abdomen body plan of a spider. The locomotory behavior of jumping spiders (Salticidae), which often share a leafy habitat with these clerids, could serve as the selection factor towards an antipredatory mechanism evolved by a variety of photophilic beetles. I (Opitz, 2004: 13) observed “jumping” behavior among plocamoceran clerids and suggested that such behavior was associated with fly-escape behavior as described by Hespenheide (1973: 52) for species of Epiphloeus Spinola.

One may also speculate that this mimetic complex, which includes Aphelocerus, involves a mimetic relationship in which the similar color, smooth body, and very similar habitus of various species of beetles and spiders may possibly be intertwined in a Mullerian association. Hespenheide (1973: 52) describes a similar mimetic complex in which beetles imitate the reddish forebody coloration and quick flight escape behavior of tachinid fly models. Moreover, Poinar (1999: 10) suggests that beetles with smooth bodies, characteristic of some of the above mentioned aphelocerans, are often characteristic of leaf beetles that escape predation by ants in that the beetles are difficult to grasp because of the smooth contour of their bodies. Lastly, Hespenheide (1987: 53) commented on the color and habitus similarity between the zygopine weevil genus Lissoderes and the otidocephaline weevil genera Myrmex and Ooterinus, and he noted that species of Aphelocerus belong to this black, strongly shining assemblage of beetles.

Floral Associations

Although checkered beetles are thought to be predominantly predaceous on lignicolous insects, they frequently occur within flowers. Checkered beetle anthophily has been reported by Foster (1976: 64), Mayer (1976: 2), Crowson (1964: 303), Hawkeswood (1981: 125, 1982: 31), and Opitz (2002: 241). To my knowledge there are no published reports of anthophily among the species of Aphelocerus. However, information from specimen labels suggests that the members of several Aphelocerus species do frequent blossoms, although their role in such a niche is unknown. According to information from specimen labels, anthophily among apheloceran species has been reported by James E. Wappes (A. leucomelas [Chevrolat] specimens feeding on blossoms of a woody plant), Jose A. Clavijo (A. sturnus Kirsch beetles within blossoms of Inga marginata), Frank T. Hovore (A. cohibilis, n.sp., individuals from a flowering tree species of Croton), and Frode Ødegaard (A. catie, n.sp., beetles on Guatteria dumetorum, Jacaranda copala, Nectandra purpurascens, and Inga cocleensis, and A. myrmecoides, n. sp., in flowers of Forsteronia myriantha).

Because apheloceran specimens have been captured on a variety of flower blossoms, one might presume that they feed on pollen. However, the construction of their mouthparts and development of the digestive system suggest that the flower visiting aphelocerans are predators of flower-visiting insects or soft-bodied arthropods. However, Frode Ødegaard reports (personal commun.) that specimens of A. catie, n.sp., did not feed on small anthophilic arthropods when the clerids and other small arthropods were placed together in small vials. Therefore, the possibility that these clerids feed on pollen and nectar cannot be discounted as both of these flower products serve to nourish other checkered beetles of the subfamily Clerinae (Opitz, 2002). Moreover, Ødegaard observed abundant specimens of A. catie, n.sp., scurying among inflorecenses of Inga cocleensis, which is very reminiscent of the flower foraging behavior of Eleale aspera Newman (Opitz, 2002: 243).

Indeed, within the Cleridae there seems to be a positive correlation between an abundance of integumental pubescence and an anthophilic life style. For example, members of the Holarctic genus Trichodes (Foster, 1976: 65), Chilean Calendyma (Crowson, 1964: 303), and Australian Eleale and allies (Hawkeswood, 1982: 31; Opitz, 2002: 241) are among the outstanding examples of the degree of pubescence-anthophilic life style correlation. The functionality of the correlation, of course, is that a densely setose integument, particularly on the insects' dorsum, would facilitate a pollen harvest, much like the densely setose pollen baskets facilitate pollen collection of the honeybee.

Further, in Aphelocerus there exists an interesting transformation of elytral pubescence in the development of the elytral middiscal setal tuft. Also, there seems to be a gradual reduction of the dense elytral pubescence from members of the more primitive leucomelas species group towards the less and less pubescent condition in the more advanced scutellaris–myrmecoides–formicoides line of species groups. Members of the batesi species group (for example, A. catie, n.sp.) and ciliaris species group (for example, A. ciliaris, n.sp.), which have highly setose elytra, have been reported on blossoms (Rifkind, personal commun.). Conversely, members of the more derived scutellaris–myrmecoides–formicoides line have an increasingly glabrous elytral disc (fig. 164). The latter species groups are clearly involved in mimetic life styles. In some of these mimetic species, such as A. formicoides, n.sp., where the body dorsum is relatively glabrous, elytral pubescence would detract from the deception to look like a more glabrous cuticular body model such as found in an ant. Conversely, members of A. eriodes, n.sp., with their clearly arachnoid body form, are densely setose on the dorsum, suggesting the trichose dorsum of a spider model. I have often wondered whether an investigation into the relationship between the intricacies of integumental pubescence and form of life style might not lead to significant evolutionary hypotheses within Cleridae.

Field Observations

During an expedition to Los Altos de Panama, January 2, 2002, the last day of fieldwork, Lee Herman and I decided to make one more attempt to obtain specimens of apheloceran species known to occur on Cerro Campana (fig. 1d), and possibly obtain biological information about them. This was my third attempt to learn something about the biology of the apheloceran species known to occur in the Cerro Campana highlands (fig. 1d). I had worked the mountain several times before but was unsuccessful at observing apheloceran life habits, or determining the whereabouts of their immature stages. About one hour before the fieldwork was to end, I found what had eluded me for quite some time, checkered beetles flying into a recently felled tree trunk with a particularly strong fragrance emitted from exposed cuttings of wood and leaves.

According to Orlando Nuñes, an indigenous Panamanian living in the area, this particular tree had been down for seven days. Among the checkered beetles that this tree attracted were 12 specimens of Enoclerus insidiosus (Gorham), eight of another Enoclerus sp., two specimens of Ichnea, one of Madoniella erythrocephalus (Gorham), and most relevant to this study, two specimens of A. myrmecoides, n.sp., scurrying among some 11 specimens of Myrmex weevils. The tree in question did not show any evidence of flowers. In addition to these beetles, I observed and then collected two specimens of bostrichids that were in the process of boring into a debarked portion of the aforementioned tree trunk. It was an exciting moment to finally observe some evidence suggesting that aphelocerans are attracted, as are many other checkered beetles, to tree volatiles and at least potentially seem involved in predatory activity associated with lignicolous insects. As A. myrmecoides, n.sp., has also been observed to frequent blossoms of Forsteronia myriantha (loc. cit.) it seems likely that at least some members of Aphelocerus are omnivorous since they may consume nectar and pollen from blossoms and prey on lignicolous insects when blossoms are not available; perhaps their diet comprises both plant and animal matter.

An interesting sidebar to the most recent field experience on Cerro Campana, Panama, was a legendary story by Orlando Nuñes about the felled tree on which I found many clerids. It seems that the indigenous peoples of Panama, possibly members of the tribe Gnobe Bugle or “ Guaymies”, made use of this species of tall tree as observation towers, and when a Spaniard asked a native about the name of this tree, the native replied in broken Spanish “espaber”, literally meaning “I climb to see”. Thus evolved the legendary vernacular name of this tree which ended a last hour of fieldwork on a culturally rich and scientifically rewarding note.

During three excursions to the charming village of Volcan, nested in a volcanic crater (1344 m) and surrounded by the highlands of Chiriqui, in Panama, I encountered many specimens of Aphelocerus chiriqui, n.sp., in two particular habitats. The first involved a natural reserve known as Hacienda Las Lagunas del Volcan, whose primary lakeside forests have trailside vegetation laden with woody shrubs densely intermixed with herbaceous vines (fig. 1c). Numerous A. chiriqui adults were taken at this site during May and August by beating. It was puzzling at first to realize that very few of these clerids could be seen scurrying on the surface of the broad vine leaves. Yet, beating this assemblage of vegetation consistently yielded specimens. Eventually, I realized that these clerids, along with a variety of other beetle predators, were foraging primarily on the underside of the leaves (as seen in fig. 1a) and along the stems of the herbaceous vines, possibly consuming immature/adult homopterans such as membracids, or feeding on the eggs of the multitude of chrysomelids ovipositing on the underside of leaves.

The second, “hot spot” for aphelocerans and other clerids (in the aforementioned highlands) was located on the northeastern slopes of a Chiriqui mountain (about 6 km north of Volcan, at about 1500 m) within an escarpment through which daily gusts of wind sweep towards and up the mountain slopes. Specimens were collected along a narrow, roughly paved winding road with overhanging herbaceous plant assemblages. Beneath the overhanging verdure one would, almost invariably, find patches of flowering Impatiens, whose presence served as indicator plant species for the potential collecting of checkered beetles. Apheloceran checkered beetles, like impatience plants, are found most often on sun-intensive moist slopes. After several days of fieldwork it became obvious that this particular portion of the mountain escarpment, with its wind thrusts, swept a variety of insects, including taxonomically diverse species of clerids, onto the slopes of the mountain, especially during midmorning periods of intensive sunlight (usually about 10:00 a.m.). Collecting efforts were poor along the same mountain road (leading to Rio Sereno from Volcan) on slopes that were shaded and where wind gusts were minimal or absent.

Most recently, during May 2002, Lee Herman and I spent a week collecting in Selva Negra, a private preserve of virgin cloud forest in the western highlands of Nicaragua. The Kühl family, a gracious people of German ancestry, is profoundly dedicated to the preservation of the Nicaraguan jungle habitats. Selva Negra (“Schwarzwald”), essentially a community of Nicaraguan citizens, maintain the mountain resort with a management style that emphasizes organically grown products within an uncompromising conservation framework.

Along the “Cody” trail, which is proximal to a large pond and adjacent to a narrow extension of a coffee grove that eventually coalesces with a dense virgin cloud forest known as “Monkey Territory”, I experienced outstanding results in the collection of generically diverse checkered beetles. Among the catch, there were two new species of Aphelocerus (A. cirritus, n.sp., and A. capillus, n.sp.) that were collected by beating overhanging tree branches, along the trail, intertwined with wild grape and other vines. Some of the nonliving vegetation, such as hardwood branches, was particularly rich in Cerambycidae.

Natural History InformationFrom Specimen Lables

Many of the specimens on which this treatise is based were collected by beating tree foliage, particularly oak trees in tropical forests. Label data suggest that aphelocerans may be collected on foliage or woody branches of the following plants: Nectandra purpurascens, Calophyllum longifolium, Inga cocleensis, Maranthes panamense, Lysiloma divaricata, Spondias mombin, Brosimum alicastrum, B. utile, Inga marginata, Forsteronia myriantha, Coumarouna oleifera, and species of Piper, Acasia, Quercus, Croton, and Arum (an epiphytic vine).

Although specimens were collected throughout the year, most were captured from May through July, at elevations ranging from 97 m to 3000 m, most collected between 1500 and 2000 m. The “beating-sheet” method of collecting seems to be the most productive manner of obtaining these insects, although some specimens were also collected with sweep nets, light traps, and Malaise traps.

COALITUS GROUP Aphelocerus leucomelas (Chevrolat) Figures 29, 30, 54, 126, 127, 190, 255, 257, 259; map 3

Aphelocerus coalitus, new species Figures 9, 27, 31, 55, 97–101, 128, 129, 155; map 4

ECHINATUS GROUP Aphelocerus echinatus, new species Figures 51, 125, 144b; map 21

Aphelocerus affaniatis, new species Figures 85, 144a; map 4b

CILIARIS GROUP Aphelocerus ciliaris, new species Figures 25, 48, 91–94, 154, 207, 208, 255b, 260; map 1

Aphelocerus citimus, new species Figures 53, 123; map 21

BISPINEUS GROUP Aphelocerus delicatulus (Barr) Figures 193, 256; map 24

Aphelocerus aeneus, new species Figure 196; map 27

Aphelocerus bispineus, new species Figures 52, 194, 195, 255a; map 21

Aphelocerus acuticolis, new species Figures 197, 215, 235; map 27

ACANTHUS GROUP Aphelocerus primigenius, new species Figures 216, 243; map 27

Aphelocerus sturnus Kirsch Figures 82, 160, 183; map 16

Aphelocerus acanthus, new species Figures 81, 150, 181; map 14

Aphelocerus inconstans (Gorham) Figures 20, 26, 28, 49, 121, 122, 184–186, 244, 269; map 2

Aphelocerus cirritus, new species Figures 262, 263, 270, 274; map 4a

Aphelocerus patulus, new species Figures 38, 71, 141, 254; map 21

Aphelocerus chiriqui, new species Figures 75, 159, 175, 258; map 21

SCULPTILLUS GROUP Aphelocerus sculptillus, new species Figures 137, 198, 217, 240; map 27

Aphelocerus sabulosus, new species Figures 199, 239; map 27

Aphelocerus chondrus, new species Figures 73, 213, 249; map 27

Aphelocerus cohibilis, new species Figures 218, 239, 248; map 27

IRRORATUS GROUP Aphelocerus irroratus, new species Figures 34, 63, 132; map 9

IMMARGINATUS GROUP Aphelocerus immarginatus (Chevrolat) Figures 39, 40, 76, 139, 242; map 13

YUNGAS GROUP Aphelocerus acutus, new species Figures 61, 105, 106, 130, 133, 169, 268; map 7

Aphelocerus torosus, new species Figures 265, 267, 275; map 27

Aphelocerus olanchoensis, new species Figures 276, 277; map 27

Aphelocerus vietus, new species Figures: 140, 252, 253; map 27

Aphelocerus turnbowi, new species Figures 209, 220, 233; map 25

Aphelocerus cornuatus, new species Figures 60, 167; map 21

Aphelocerus humerus, new species Figures 67, 114, 115, 168; map 21

Aphelocerus domus, new species 50, 96, 223, 232; map 25

Aphelocerus capillus, new species Figures 153a, 266; map 10

Aphelocerus coactus, new species Fronticepiece, figs.1a, 10, 12–14, 16, 17– 19, 21, 57, 95, 102–104; 156, 241; map 5

Aphelocerus scalenus, new species Figures 204, 219, 221, 236; map 26

Aphelocerus yungas, new species Figures 78, 142, 176, 182, 222, 230; map 22

Aphelocerus extensivus, new species Figures 37, 66, 158; map 27

BATESI GROUP Aphelocerus lividus, new species Figures 59, 107–109, 131, 170; map 8

Aphelocerus nitidus (Chevrolat) Figures 2–8, 15, 33, 58, 157, 234, 237, 261, 271; map 6

Aphelocerus sagittarius, new species Figures 62, 110–113, 135, 136, 165; map 21

Aphelocerus triangulus, new species Figures 65, 118, 119, 166; map 21

Aphelocerus batesi, new species Figures 79, 152, 179, 272; map 15

Aphelocerus ebenus, new species Figure 205; map 25

Aphelocerus catie, new species Figures 74, 144, 174; map 12

Aphelocerus monteverde, new species Figures 72, 177, 214; map 21

Aphelocerus arenatus, new species Figures 70, 120, 134, 173; map 21

Aphelocerus bufustis, new species Figures 32, 80, 151, 180, 273; map 22

Aphelocerus anticus, new species Figures 77, 178, 211; map 22

Aphelocerus naevius, new species Figures 35, 36, 64, 116, 117, 143; map 21

Aphelocerus protenus, new species Figures 69, 138, 171, 251; map 21

Aphelocerus argus, new species Figures 68, 124, 172; map 25

PANUS GROUP Aphelocerus panus, new species Figures 43, 89, 148, 245; map 18

Aphelocerus hespenheidei, new species Figures 206, 247; map 25

Aphelocerus collaris, new species Figure 246; map 26

FORMICOIDES GROUP Aphelocerus dispilis, new species Figures 44, 46, 86, 162, 264; map 20

Aphelocerus formicoides, new species Figures 45, 47, 87, 149; map 23

CHELIFEROUS GROUP Aphelocerus akis, new species Figures 200, 201, 226; map 25

Aphelocerus chelonus, new species Figures 202, 203, 227; map 25

Aphelocerus cheliferous, new species Figures 88, 146, 147, 192, 228; map 19

SCUTELLARIS GROUP Aphelocerus scutellaris (Chevrolat) Figures 41, 42, 84, 145; map 21

Aphelocerus improcerus, new species Figures 210, 225, 231, 250; map 25

Aphelocerus propinquus, new species Figure 224; map 25

Aphelocerus calvus, new species Figures 90, 153; map 22

MYRMECOIDES GROUP Aphelocerus myrmecoides, new species Figures 11, 22–24, 83, 161, 164, 187–189; map 17

Aphelocerus inbatus, new species Figures 56, 212, 229, map 25

Aphelocerus eriodes, new species Map 26

Aphelocerus discapillus, new species Figures 191, 264; map 25

Characters Selected for Phylogenetic Analysis

Thirty-eight adult characters of Aphelocerus Kirsch and the outgroup genera Placopterus, Caestron, Perilypus, Colyphus, Sallea, Blaxima, Phonius, and Systenoderes were used in the species-group analysis. All of the outgroup genera involve New World clerine genera that I consider to be the most closely related taxa of Aphelocerus. Character states delsignated as “0” are considered plesiomorphic whereas those given a value from “1” to “6” (in the case of transformation series) are judged apomorphic.

Phylogenetic Analysis

A character matrix was coded for the 15 species-group taxa (the outgroup involves representative species of more than eight generic taxa) listed in table 1 and encoded into Hennig 86. The analysis yielded one phylogenetic tree (fig. 278) with a length index of 32, consistency index of 84, and retention index of 85.

Phylogenetic Scenario for the Evolution of Aphelocerus and Its Species Groups

It is hypothesized that ancestral Aphelocerus diverged on the land mass comprised of the ancient Mexican/Mayan blocks, that is, somewhere after the major Tertiary tectonic events. An earlier evolution of the genus is not supported by features of the external or internal morphology, or by any other line of evidence, in that an earlier Tertiary origin for Aphelocerus would likely have generated substantially more structural divergence than is presently known. Moreover, had aphelocerans been part of the great Tertiary tectonic events, the vicariant divisions and geographic shifts of the ancestral apheloceran populations would have provided tremendous evolutionary inertia, as has been demonstrated for other forms of life that “went along for the ride” during ancient Caribbean plate tectonics (Rosen, 1974, 1976; Pregill, 1981; Hallam, 1981).

The extent of generic memberships of the outgroup (fig. 278), based on the presence of the elytral trich, has not been fully established. However, it is clear that during the evolutionary ascension from ancestral species A towards ancestral Aphelocerus (ancestral species B), the elytral trich was retained. During this ascent, the ancestors of extant aphelocerans also evolved such novel characteristics as development of a clearly defined sutural tuft, and among most species, the consolidation of 2° setae into some sort of elytral tuft most prominently visible in the acanthus species group.

During the early evolution of apheloceran ancestor B, two major assemblages diverged. One of these ultimately evolved descendants characterized by aggregates of white 2° seta on the elytra. In the second lineage of this initial divergence of the apheloceran progenitor, and beginning with ancestor D, the elytra were transformed towards a more rotund configuration. It is suggested that this evolution, featured by a more compact, shorter, and more convex body form, represents a progression towards a mimetic life style involving spiders, ants, and Myrmex weevils. A gradual transition of convexity may be seen when one compares members of the panus species group with members of the scutellaris–myrmecoides lineages. Among these extant species groups one can clearly see the anatomical perfection towards ants as exibited by members of the formicoides species group that is hypothesized to be an offshoot of ancestral species L.

Ancestral species L also generated a line whose body morphology became more compact and whose general fascies proceded towards a resemblance to leaf-inhabiting jumping spiders and weevils. The sister group relationship between the scutellaris species group and the myrmecoides species group is strongly supported by such conspicuous synapomorphies as digitiform parameres, presence of frontal and pronotal setal tufts, and a very strong evolution towards mimicry. In time, ancestral species M diverged to produce the scutellaris–myrmecoides species groups, any member of which converged towards the body plan of jumping spiders and/ or Myrmex weevils (compare figs. 163 and 164).

From the progenitor of Aphelocerus (ancestral species B) there apparently evolved a stem species (ancestral species C) that retained the plesiomorphic, more flattened elytral structural plan characteristic of the majority of the species in the genus. The divergence of ancestral species C evolved into a line in which the elytral surface became scabrous. It is hypothesized that eventually this line evolved into ancestral species E that, in turn, diverged to produce ancestral species G and H.

Ancestral species G generated the sister species groups coalitus and echinatus, both characterized by their retention of asetiferous punctations. Ancestral species H produced the ciliaris–bispineus lineage in which the 2° elytral setae demonstrate a trend towards consolidation. White 2° setal aggregates towards development of an elytral patch becomes progressively more prominent as one proceeds towards the irroratus–yungas species-group members.

In summary, there are three major evolutionary trends among the extant species of Aphelocerus. The first, and most conspicuous, involves the progressive increase of elytral convexity as we proceed from the panus species group and end with the scutellaris species group. The second trend involves the development of 2° setae on the elytra as is seen from the coalitus species group to the bispineus species group. Lastly, there is a progressive consolidation of 2° setae into setal patches on the elytra, which reaches its most complex development among the acanthus species-group specimens. Then, there is a curious characteristic reversal; one hypothesizes a reduction of the posterior patch of the 2° elytral setal tuft. This reversal is most clearly evidenced in the batesi species group.

Zoogeographic Considerations

Many outstanding advances have been made in biogeography from the pioneering Darwinian concept of center of origin and dispersal. The panbiographer Croizat (1964) advanced the idea that contemporary macrobiotic distributions may be placed into historical context by the establishment of faunal tracks, tracks that faunistically unite intercontinentally and thus potentially foretell, or suggest, patterns of historical distributions of species ancestral to the extant species under study. Faunal tracks are established by plotting corroborative distributional linearities of distantly related faunas and floras.

Rosen (1978: 160) refined Croizat's concepts into a methodology called vicariance biogeography whereby tectonic events are acknowledged to fragment ancestral biotas into geographical separation. Subsequently, these now separated biotal fragments may or may not respond evolutionarily following the vicariant event. If evolutionary inertia does take place, that is, if through natural selection, or through any other process involved with speciation, the biota fragmentation evolves novelties, and possibly obscure ancient synapomorphies, then the kinship relationship may well be inferred with usage of the vicariance biogeographical model. In essence, the vicariance concept involves the fragmentation of ancestral faunas towards an insular existence of the resultant vicariants.

With a focus on Mexico and Central America, Halffter (1987) suggested that the extant insect distributions of the Mexo-America (as defined by fig. 282) and Nuclear Central American (as defined by fig. 284) faunas are explainable via transitional zoning. Halffter's biographic concept considers temperate and tropical montane habitats the primary basis for northern and southern encroachments of insect biotas into the aforementioned landmasses. More recently, Liebherr (1991a) applied cladistic biographical methods to derive general area cladograms for the montane areas of Mexico on the basis of cladistic analyses of the carabid genera Elliptoleus and Calathus.

Despite these important advances in biogeography, I am compelled to reiterate an earlier thought about the use of biogeographic methods: “Irrespective of biotic or taxonomic level, it is the nature of the available data that usually determines the approach to historical zoogeography” (Ekis, 1977: 126), particularly among systematic entomologists who often struggle with a paucity of distributional records.

Lastly, cladistic biogeography suggests that distributions of extant taxa reflect results of physiogeographically based historical vicariances. This concept of biogeography is more likely to be supported by ancestral or more primitive extant taxa simply because there has been more time to evolve phylogenetically useful characteristics that can support of refute biogeographical hypotheses. In many instances, however, the cladistic biogeographical model is difficult to apply when one deals with species-level faunas that have undergone, or are undergoing, rapid evolution in relatively recent geologic history. In such cases, there has not been sufficient time for establishment of synapomorphic diversity upon which to base hypotheses of evolution or historical biogeography.

Geophysical Orismology

In biogeographical analyses it is important to define geophysical parameters. How one partitions the research terrain is often dependent on the vagility of the organism under consideration, the extent of ecological specialization of the species, the geographical extent to which the research animal has been collected, and the extent of the motivation of the investigator to provide extant/historical explanations of currrent distributional patterns. In the recent decades, there has been a flurry of important discussions relevant to the geophysical properties if Middle America (Malfait and Dinkman, 1972; Keigwin, 1982; Coney, 1982; Burke, et al., 1984; Weyl, 1966; and Donnelly, 1988). Moreover, in Systematic Entomology, the works of George Ball (e.g., 1978) and his students (Erwin, 1970; Whitehead, 1972; and Noonan, 1973), and Liebherr (1988, 1991, 1991a, 1992, and 1994) have greatly advanced our thinking about Middle American insect biogeography.

The above mentioned works, and others, have been important resources for my thoughts about Middle American checkered beetle biogeography. Checkered beetles are a particularly difficult group to analyse biogeographically because of the difficulties associated with their collection. They are rarely collected in great numbers, as a group are comprehensively involved in mimicry (Mawdsley, 1994), and are few in numbers per locality, and are sometimes associated with floral periodicity (Opitz, 2002: 241). However, I can state with confidence that most of the Middle American checkered beetle fauna is found most abundantly in midaltitude highlands, usually at about 1000 m. The prominent association of checkered beetles with temperate and tropical montane regions, in combination with some recent information about Middle American tectonics and historical orogeny, suggests, at least for checkered beetle biogeography, a subdivision of the New World into seven major divisions. These divisions although generally alligned with political boundaries are established to focus more on the major mountain ranges from which checkered beetles have been collected in abundance.

North America (fig. 279): The northern continental landmass south to the political boundary with Mexico and corresponding roughly with the diminution of the more southern ridges of the Rocky Mountains.

Middle America (fig. 280): The landmass extending southeast from the United States to the southeastern highlands of the Cordillera de San Blas of Panama.

South America (fig. 281): The southern continental landmass extending east and south from Panama and more or less in its westernmost region, corresponding to the distribution of the Colombian–Venezuelan Andes to the southern foothills of the Chilean Andes.

Mexo-America (fig. 282): The terrain south of the United States and approximately compatible with three great mountain chains, the Sierra Madre Occidental, the western component of the Transvolcanic Sierra, and to the southern foothills of the Sierra Madre del Sur. This subdivision ends at the southermost limit of the isthmus of Tehuentepec and geologically consists of the Mesozoic Mexican Block (Donnelly, 1988: 17).

Central America (fig. 283): The landmass east of the Isthmus of Tehuantepec, then extending eastward and southward to the border of Colombia. The terrain includes the Talamancan range of Costa Rica and Panama and the Cordillera of San Blas in eastern Panama. The northern half of this landmass remained above sea level thoughout the Cenezoic, whereas the southern half was submerged throught the majority of the Tertiary (Savage: 1982: 465).

Nuclear Central America (fig. 284): The portion of Central America extending from the Isthmus of Tehuentepec southeastward to the highlands of eastern Nicaragua. In essence, this terrain roughly corresponds to what has been called the Chiapas Complex (Ball and Shpeley, 2000), and involves the pre-Mezozoic Mayan and Choris Blocks. Although there was considerable tectonic rearrangement of these crustal areas during the development of the Caribbean portal, convention has it that they were connected to the Mexican Block and consistently above sea level during the Tertiary. It is believed that the Choris Block connected to the Mayan Block at the end of the Cretaceous and tectonocally acquired its present position at about 30 million years ago (Donnelly, 1988: 21).

Insular Central America (fig. 285): The southern portion of Central America located between southern Nicaragua and Colombia and involving the Costa Rican- Panamanian highlands of Sierra Talamanca and the Panamanian Cordillera San Blas. It is widely known that this terrain was submerged during the greater part of the Tertiary and formed the Pacific and Atlantic portal. The closure of this portal began some 25 million years ago (Keigwin, 1982; Donnelly, 1988), and allowed interchanges of flora and fauna between North America, Mexo-America, Nuclear Central America, and South America.

As a group, the aphelocerofauna is in a rapid state of evolution, as the general anatomical coherence within the group suggests. The species members of the batesi and yungas species groups are particularly similar in general anatomy. It is unlikely that their present distributions can be linked to Tertiary orogenic and/or tectonic events. In the genus, there are an outstanding number of cryptic species. In particular, there are a variety of cryptic species within the batesi species group whose members exhibit the most extensive geographic distribution within the genus. Cryptic species are common in other apheloceran species groups as well. Therefore, it is unlikely that the present distributions of the more recent apheloceran species groups can be linked to tertiary orogenic and/ or tectonic events. Moreover, of the 66 species presently recognized, fully 54 are confined to single mountain complexes (see figs. 286, 287). When one deals with such recent faunas, area cladograms based on historical geologic events must give way to models implementing biographical methods of dispersal and transitional zoning.

The limited range of many of the species suggests that Aphelocerus is undergoing rapid evolution, principally in isolation, in montane Middle American (fig. 286) and montane northern South America (fig. 287) highland complexes. In my view, this suggests that the ancestral apheloceran divergences occurred after the principal Tertiary tectonic events. Therefore, in an attempt to present some beginnings of a biogeographical analysis of this genus, I will implement the “transitional zone” method as defined by Marshall and Liebherr (2000) and proposed by Halffter (1987).

However, when dealing with the ancestors of Aphelocerus, in connection with the distribution of extant taxa closely related to that genus, some preliminary historical biogeographical comments might be worthy of discussion. Distributional evidence suggests that ancestral Aphelocerus evolved on an ancient Middle American terrain, probably on what is commonly referred to as the Mexican and Mayan Blocks. These were prehistoric crustal areas that fused tectonically to the northern continent as far back as Albanian time, some 100 million years ago (Donnelly, 1988: 19). These blocks must have been exceptionally fertile grounds for some clerine lineages as today regions that correspond to these ancient land masses harbor a variety of monotypic taxa that undoubtedly represent surviviors of a much more diverse Tertiary fauna.

Perhaps, many of these ancestral kindreds of Aphelocera, which led to such older groups as Blaxina and Sallea, succumbed to the Yucatanian Bolide impact thought to have occurred at the end of the Cretaceous (Alvarez and Asaro, 1990). Having survived the Bolide impact, ancestral aphelocerans, and those of the lesser speciose cousins, apparently proved more adaptable to the incipient habitats that persisted following the Bolide impact. Aphelocerans probably flourished during the post Bolide impact periods, as did such genera as Colyphus, Perilypus, and Placopterus. These genera, along with the very speciose Enoclerus, proceeded to proliferate into available niches on the more favorable southern habitats. Such habitats would have been provided by tectonic events such as the addition of the Chortin Block to the Mayan Block thereby increasing the area of more tropical environs and completing the development of what has come to be known as Nuclear Central America.

In time, there would have been the closing of the Panamanian portal, allowing a southern apheloceran dispersal that proliferated a number of species across species group lines, and generated such derived groups as the autochtonous sculptillus and myrmecoides species groups. It is difficult to add credible biographical comments about the South American aphelocerofauna. On the basis of what is known, it seems that this fauna stems from multiple southern extensions of Middle American elements. What can be stated with confidence, however, is that these tentative statements about Aphelocerus biogeography will have to be reevaluated when the South American aphelocerofauna is more thorougly known. I believe that there are vastly greater number of apheloceran species in South America than have heretofore been dicovered.