Checklist of the Pteridophytes of Aguascalientes , Mexico

Ferns and fern allies from Aguascalientes, Mexico were studied. Fifty-five localities distributed in all municipios of the state were surveyed. Seventy-seven taxa were found: seventy species of ferns, five species of Selaginella, one species of Equisetum, and one species of Isoetes. Forty taxa are new records for Aguascalientes. Among the ferns, Cheilanthes and Polypodium are the most diverse and abundant genera, usually occurring in xerophytic associations or dry forests. Selaginella is also common in Aguascalientes, and inhabits rocky cliffs in dry environments. Equisetum and Isoetes are restricted to marshy places.


INTRODUCTION
Aguascalientes is the third smallest state of Mexico at 5589 krn -.It is located between 21 °38'03"N and 22°07'06"W in the central part of Mexico.In the north.east and west, it is bordered by Zacatecas. and to the south by Jalisco.Aguascalientes is divided into II municipios (counties): Aguascalientes , Asientos, Calvillo, Cosfo , EI Llano, Jesus Marfa, Pabe1l6n de Arteaga , Rinc6n de Romos, San Franci sco de los Romo, San Jose de Gracia, and Tepezala (Fig .I).A great central plain with some low elevations is the predominant physiography of Aguascalientes.Xerophytic scrub w ith thorny elements (Acacia farn esiana (L.) Willd., Prosopis laevigata (Humb.& Bonpl.ex Willd .)M. C. Johnst., Mimosa biuncifera Benth ., Opuntia streptacantha Lem ., etc.) is the most common vegetation of the central plain.In the northwest, there is a mountainous region with an elevation that ranges from 1570 to 2900 m.It is dominated by Juniperus, Pinus, and Quercus forest associations.In the southwest, there is a small subtropical scrub area with Bursera fagaroides (Kunth) Engelm., Ficus petiolaris Kunth, Leucaena esculenta (DC.)Benth., Lysiloma microphyllum Benth., and Myrtillocactus g eom etri rans (Mart.)Console as dominant elements (De la Cerda and Siqueiros 1985).The climate of Aguascalientes is semi-dry with a n average temperature and precipita-tion of 17.4°C and 526 mm, respectively (Anonymous 1981 ).
Botanically, Aguascalientes was barely explored until 1980 , when the "Flora del Estado de Aguascalienres" project was initiated.Aquatic plants, cacti , grasses, medicinal plants, legumes, oaks, pines, and composites among others have been published (De la Cerda 1996, 1999a, b ;Garcia 1999a, b;Siqueiros 1996Siqueiros , 1999a, b), b).The pteridophytes of Aguascalientes have been little studied.Mickel (1992) and Rzedowski and McYaugh (1972) c ited 37 and seven species, respectively.This study thus expands our knowledge of the ferns and their allies, documenting 77 species of pteridophytes in Aguascalientes, following the class ification used by Mickel (1992) and Flora of North America (1993).We include in " pterido phytes " ferns and fern allies, as traditionally construed (Knobloch and Correll 1962;Smith 1981;Mickel and Beitel 1988;Lellinger 1989;Mickel 1992).Although, we know now that " pte ridophytes" are not a natural group (Duff and Nickrent 1999;Soltis et a1. 1999 ;Pryer et al. 2001), we still use this term since it includes plants with a similar life history and standing at a similar evolutionary level (Mickel 1992).
10. San lose de Gracia.I I. Tepezala , tes, their distribution, and habitat.The study included plants collected throughout the state over several years.Fifty-five localities distributed in all municipios were surveyed.We also included herbarium specimens from GUADA, HUAA, MEXU, RSA-POM, and US, as well as literature records (Rzedowski and McVaugh 1972;Mickel 1992).Pteridophytes were identified using various treatments (Tryon 1956(Tryon , 1957;;Knobloch and Correll 1962;Knobloch 1976;Gregory and Riba 1979;Mickel 1979Mickel , 1992;;Smith 1981Smith , 1993;;Aguirre 1983;Palacios-Rios and Riba 1983;Pacheco and Lorea-Hernandez 1985;Mickel and Beitel 1988;Palacios-Rios 1990;Tryon et al. 1990;Mickel and Valdespino 1992;Windham 1993;Moran and Riba 1995) .The pteridophytes checklist is organized alphabetically by genus and species, following the Mickel (1992) treatment.Family names follow Flora of North America (1993).The checklist includes locality, organized alphabetically by municipio, vegetation type, elevation (except for species cited in the literature), collector, and collection number.For collections lacking a collection number (s.n.) the herbarium accession number is provided.All specimens are from Aguascalientes and are deposited at HUAA, unless otherwise indicated.Several specimens obtained from literature citations (not seen) lack herbarium references.

RESULTS AND DISCUSSION
We found 77 species of pteridophytes in Aguascalientes.These included 70 species of ferns, five of spike mosses (Selaginella) , one of quillworts (lsoetes) , and one of horsetails (Equisetum).Forty (52%) were new records for Aguascalientes and are annotated on the checklist by an arrow.
In Aguascalientes, ferns are more widely distributed than their allies tEquisetum, Isoetes and Selaginella).

AC KNOWL EDGMENTS
Thi s study was funded by the Un iversidad Aut6nom a of Agu ascalientes.We thank our co lleagues from HUAA, M argarita de la Cerda, Carl os Da vila, Gerardo Garcfa , and Octavio Rosales, who supported the field wo rk, Steve Bo yd and Rosa Cerros w ho kindl y revie wed the first dra ft of thi s paper, Alan R. Smith for his co nstruc tive and pertinent suggestions, curators from various herbari a, and many other s who made this study pos sible.
Genera such asAstrolepis, Bommeria, Cheilanthes,  Elaphoglossum, Notholaena, Pellaea, Phlebodium,  Pleopeltis, andPolypodium are found growing in xerophytic scrub or dry forest habitats.Usually they are epipetric and, after a dry period, able to quickly rehydrate when water is again available.Anogramma, Asplenium, Botrychium, Cystopteris, Dryopteris, Mildella, Pteridium, and Woodsia require soil moisture and occur in shady places in a variety of habitats, such as open, high grasslands, humid oak forests, or subtropical areas.Adiantum, Osmunda, and Thelypteris are found in wet areas and stream banks in tropical conditions .Azolla and Marsilea are restricted to aquatic or subaquatic habitats.Cheilanthes is the most diverse and abundant genus in Aguascalientes with 14 taxa, followed by Polypodium with six species, and Pellaea and Asplenium with five .Pellaea is very abundant, present in nearly all plant associations.Anagram- ma leptophylla was found only at one locality in the state.Among the fern allies, Selaginella is the most abundant epipetric genus and is represented by five species.It is very common throughout the state, especially S. lepidophylla and S. rupincola.Isoetes and Equisetum are represented by only one species each, and are restricted to marshy places in Quercus-Pinus forest and subtropical scrub, respectively.Even after extensive searching, we were unable to locate populations of Argyrochosma formosa, Astrolepis beitelli, Cheilanthes eatonii, and Polypodium subpetiolatum, which were reported for Aguascalientes by Mickel (1992) .Da vila ] 0; JES US MARiA, 4 km N o f Tapi as Viej as, Siqueiro s 26 16 ; SA N JOS E DE GRAC IA, 3 km W of La Est ancia , di sturbed sub tropical sc ru b, 210 0 m, Gard a 191 9; RIN C ON DE ROMOS, 20 km E o f Ce rro S an Ju an .24 00 m, Mc v'augh 2]748 (Mic ke l 1992 ). SELAGINELLA UNDERWOODII Hieron., in Engle r & Prarul AS IE NTOS.W slo pe of Cer ro Palm ira, se mit ho rny sc ru b, 2250 rn, S iqueiros 4]54.Quercu s-Pinus-Juniperus for est, 2500 m, Siquei ros 4]44; canyo n W of L a C ie nega, Sie rra Frfa , Que rcus -Pinus fo rest, 26 19 rn, Gonzdtez-Adame 594.WOODStA MOLLIS (Kaulf.)J. Sm.CALVILLO, Barranc a EI P ilar, Siqueiros and Davila 41 98 ; RIN CON D E ROMOS , Barranca S ierpe ns , su btro pical sc ru b with Que rcus. 2 120 m, Siq ueiros 4266; SAN JOS E D E G R AC IA , Ej ido EI Baj fo , Sie rra de San Bias de Pab ellon, Jun iperus-Quercus fore st , 255 0 m, Garda 194] ; Km 5 3, roa d to Cienegu illa fo res t sta tio n, Quercus fores t, 27 12 m, Gon ralez-Ada me 600.