Elevation gradients of diversity for rodents and bats in Oaxaca, Mexico

1 This study documents patterns of rodent and bat diversity related to abiotic and biotic factors along elevational gradients in the Sierra Mazateca (640-2600 m a.s.l.) and Sierra Mixteca (700-3000 m a.s.l.) in Oaxaca, Mexico. 2 The two transects share similar faunas: 17 and 23 rodent species were captured in the sierras Mazateca and Mixteca, respectively, 14 of which occurred on both transects. Rodent species richness was similar in the wet season and the dry season along both transects. Rodent species richness peaked at 1025-1050 m in tropical semi-deciduous forest on both transects. Endemic species were restricted to high-elevation habitats. 3 Sixteen and 17 bat species were captured in the sierras Mazateca and Mixteca, respectively; 11 occurred on both transects. Bat species richness was higher in the wet season than in the dry season in the Sierra Mazateca. Bat species richness peaked at 1850 m in pine-oak forest in the Sierra Mazateca, and at 750 m and 1050 m in tropical semi-deciduous forest in the Sierra Mixteca, decreasing abruptly at higher elevations on both transects. 4 Patterns of trophic diversity of rodents and bats coincided with those of species richness on each transect. Species richness increased with increasing habitat diversity; increased with increasing rainfall and productivity; increased with increasing resource diversity; and increased in areas with high rates of speciation (rodents only). 5 The need for conservation action in Oaxaca is urgent and proponents should promote establishment of protected areas linking lowland habitats with high species richness to high-elevation habitats harbouring large numbers of endemic forms.