Effect of an urban area in the distribution pattern and diversity of Neotropical rodents

Urbanization implies the loss of biodiversity and promotes the extirpation of local flora and fauna.  It favors habitat fragmentation and the establishment and increase of non-native species and, eventually, the homogenization of the landscape.  This study aims to evaluate the urbanization process in a medium-sized city in the Mexican southeast, San Cristóbal de Las Casas (SCLC) in the Neotropics, and the response of the rodent community to such process.  The study area was categorized according to its structural characteristics into four coverage classes: urban, forest, agricultural and mountain wetlands.  Rodents were sampled over urbanization gradients.  In each gradient, nine sampling sites were established.  The responses of rodent alpha and beta diversities to landscape structure (landscape metrics) were evaluated.  The larger diversity of rodents was found in the mosaic and transition landscape categories and the least diverse were the conserved and urban ones.  In SCLC, rodent richness responds to the number of fragments and the diversity of the landscape.  Mus musculus and Rattus rattus were more abundant in landscapes with a high percentage of urban cover, while Peromycus mexicanus and P. beatae, in landscapes with higher forest cover.  San Cristóbal de Las Casas is a city that grows over areas with native vegetation, forests and mountain wetlands; of which fragments remain embedded in the urban matrix.  Mosaic and transition landscapes favor areas with high diversity and richness of rodent species (intermediate disturbance hypothesis).  This study suggests that both native and non-native rodent species are abundant in areas with natural vegetation and also in urban sites.  Sanitary measures are granted, since reservoir species of pathogens with zoonotic potential can be found in the area.