Mammals of the Jesús María River Basin, Western Mexico: Alpha and Beta Diversity in an Area of High Environmental Heterogeneity

The Jesús María River basin in the state of Nayarit, Mexico, is located at the intersection of Nearctic and Neotropical regions in the Sierra Madre Occidental (SMO) in western Mexico. Because of its biological importance, the basin is considered a terrestrial priority region (RTP-059) by CONABIO, the institution responsible for inventorying Mexican biodiversity. Several vegetation types occur in this relatively small area (cloud and tropical forests, conifer forests, subtropical scrub). However, the area has been undersampled because of its difficult access and topographic complexity. Based on our own collections, review of museum specimens, and literature records, we recorded 92 species at 10 major sites throughout the basin. Twenty-three species are endemic to Mexico, 9 of which are endemic to the SMO. Six species were recorded for the first time in the state of Nayarit, and 2 in the state of Jalisco. These findings increased the species count for the SMO of Nayarit by 17 species. Turnover rate was high throughout the region. The number of endemisms of RTP-059 equals or surpasses that of most megadiverse protected areas in Mexico, and this area is likely to be a center of origin for several taxa. No protected areas exist within RTP-059 because its social and natural complexity makes it difficult to establish effective conservation strategies. La cuenca del Río Jesús María, en el estado de Nayarit, México, se localiza en la intersección entre las regiones biogeográficas Neártica y Neotropical en la Sierra Madre Occidental (SMO), en el oeste de México. Debido a su importancia biológica, es considerada como región terrestre prioritaria (RTP-059) por CONABIO, la institución encargada del inventario de la biodiversidad en México. Varios tipos de vegetación ocurren en esta área relativamente pequeña (bosques de niebla, bosques tropicales y de coníferas, y matorral subtropical). Sin embargo, el área ha sido poco muestreada debido a su difícil acceso y complejidad topográfica. Con base en nuestras colectas, revisión de ejemplares de museo, y registros bibliográficos, documentamos 92 especies en 10 sitios distribuidos en la cuenca. Veintitrés especies son endémicas de México, de las cuales 9 lo son de la SMO. Se registraron por primera vez para Nayarit 6 especies, así como 2 para el estado de Jalisco. Se incrementó el inventario de mamíferos para la SMO de Nayarit en 17 especies. La tasa de recambio fue alta en toda la cuenca. El número de endemismos para esta re