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.