Abstract

The Perote ground squirrel (Xerospermophilus perotensis) is endemic to Mexico and is currently at risk of extinction. Its original range comprised 5,250 km(2) in an area known as the Oriental Basin, between the states of Puebla and Veracruz. By the end of the 20th century, however, extensive agricultural practices, overgrazing, and urbanization had already restricted suitable habitat for this species to only 16 localities. Temporal changes in genetic diversity and structure in this species were assessed from 34 museum specimens from 5 historical populations (1990-1992) and 44 individuals from 3 current populations (2007) using the mitochondrial (mtDNA) control region and 5 nuclear microsatellites. We observed a general trend (significant in some cases and nonsignificant in others) suggesting a decrease in genetic diversity within populations and an increase in genetic structure between them in recent years for both sets of markers. A Bayesian skyline reconstruction for the mtDNA sequences was congruent with a recent demographic decline scenario. If genetic drift is the predominant evolutionary force in Perote ground squirrels, then the loss of genetic diversity could intensify in a few generations even if the effective population sizes remain constant. Urgent measures to increase the effective population sizes and maintain the genetic cohesion among populations are critical to the conservation of this species. Because no protected areas are planned in the Oriental Basin, we suggest translocating individuals between populations to avoid further loss of genetic diversity in the short run. In the long run, however, it will be necessary to devise a strategy to introduce individuals into suitable patches of habitat and to spatially link these populations so that genetic exchange can take place without the need for management assistance.