The freshwater snails (Mollusca: Gastropoda) of Mexico: updated checklist, endemicity hotspots, threats and conservation status

Abstract

We present an updated checklist of native Mexican freshwater gastropods with data on their general distribution, hotspots of endemicity, threats, and for the first time, their estimated conservation status. The list contains 193 species, representing 13 families and 61 genera. Of these, 103 species (53.4%) and 12 genera are endemic to Mexico, and 75 species are considered local endemics because of their restricted distribution to very small areas. Using NatureServe Ranking, 9 species (4.7%) are considered possibly or presumably extinct, 40 (20.7%) are critically imperiled, 30 (15.5%) are imperiled, 15 (7.8%) are vulnerable and only 64 (33.2%) are currently stable. With 61 species in 21 genera, the Cochliopidae are the most diverse family, followed by the Planorbidae (37 species) and Pachychilidae (31). Pachychilus is the most species-rich genus with 30 species. Despite the high number of imperiled species (84), only 7 species (3.6%) are currently listed as endangered by the Mexican Secretariat of Environment and Natural Resources. We identified 3 hotspots and 2 potential centers of gastropod endemicity. Our research serves as a first step for determining priority areas for conservation of imperiled Mexican freshwater gastropods. A. Czaja et al. / Revista Mexicana de Biodiversidad 91 (2020): e912909 2 https://doi.org/10. 22201/ib.20078706e.2020.91.2909 ResumenSe presenta un listado actualizado de gasterópodos dulceacuícolas nativos de México con datos de su distribución general, hotspots de endemicidad, amenazas y, por primera vez, su estado de conservación estimado. La lista contiene 193 especies, 13 familias y 61 géneros. De éstas, 103 especies (53.4%) y 12 géneros son endémicos de México y 75 de estas especies se consideraron endémicas locales debido a su distribución restringida a áreas muy pequeñas. Usando NatureServe Ranking, consideramos 9 especies (4.7%) posiblemente o probablemente extintas, 40 (20.7%) en peligro crítico, 30 (15.5%) en peligro, 15 (7.8%) son vulnerables y solo 64 (33.2%) están estables actualmente. Con 61 especies en 21 géneros, Cochliopidae es la familia más diversa, seguida de Planorbidae (37 especies) y Pachychilidae (31). Pachychilus (Pachychilidae) con 30 especies, es el género más rico en especies de los gasterópodos dulceacuícolas mexicanos. A pesar del alto número de caracoles en peligro (84), solo 7 (3.6%) están actualmente catalogados en peligro por la Secretaría de Medio Ambiente y Recursos Naturales de México. Identificamos 3 hotspots y 2 centros potenciales de endemicidad. Los resultados servirán como un primer paso para determinar las áreas prioritarias para la conservación de los gasterópodos mexicanos amenazados.

Subterranean freshwater gastropod biodiversity and conservation in the United States and Mexico

“…The family Cochliopidae contains the most stygosnail diversity in North America; species occur in the Appalachians, Edwards Aquifer, and Ozarks karst regions in the United States (Gladstone et al, 2019;Hershler & Figure 2. (a) Snorkel surveys for aquatic life, including stygosnails, in an Interior Plateau cave stream in Alabama, USA (photo by Amata Hinkle), (b) Bou-Rouch pump sampling in the Edwards Aquifer, USA, (c) cenote Xoch, Yucatán Cenote Aquifer, Mexico (habitat of Mexicenotica xochii) (from Grego et al, 2019), and (d) entrance of cave, Appalachians, USA (paratype locality of Antrorbis tennesseensis) Holsinger, 1990) and the Cuatro Ciénegas-Río Sabinas System, Río Verde Basin, and Yucatán Platform in Mexico (Figure 3) (Czaja et al, 2020;Grego et al, 2019;Hershler, 1985). Several other families (Amnicolidae, Emerciidae, Lithoglyphidae, and Physidae) have also colonized U.S. and Mexican subterranean waters.…”

“…Czaja et al. (2020) assessed the conservation status of freshwater gastropods of Mexico and found that 84.6% of Mexican stygosnails are threatened. Stygosnails from other regions require updated status assessments (Appendix S1).…”

“…The two largest threats facing Edwards Aquifer stygosnails were groundwater extraction and groundwater contamination (Hutchins, 2018); threats likely to be present for stygosnails in other parts of the United States and Mexico. Czaja et al (2020) assessed the conservation status of freshwater gastropods of Mexico and found that 84.6% of Mexican stygosnails are threatened. Stygosnails from other regions require updated status assessments (Appendix S1).…”

“…Coahuilix hubbsi and Paludiscala caramba are the only stygosnails on the list, called the NOM059 (SEMARNAT, 2010). However, the NOM059 has not been updated since 2010, precluding recently described, imperiled species such as Mexicenotica xochii , Pyrgophorus cenoticus , Phreatomascogos gregoi , and Balconorbis sabinasensis from protection (Czaja et al., 2020).…”

“…In Canada, Mexico, and the United States, nearly 70 freshwater gastropod extinctions have been recorded (Czaja, Covich, et al., 2019; Johnson et al., 2013). Over 75% of all extant freshwater gastropod species in Mexico and the United States are considered threatened under NatureServe criteria (Czaja et al., 2020; Johnson et al., 2013; NatureServe, 2020) (Appendix S1). On the International Union for Conservation of Nature (IUCN) Red List, 10 stygosnails species are listed as threatened (IUCN, 2020).…”