Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

Determine patterns of genetic variation at nuclear microsatellite loci among fragmented vertebrate populations that occur in patches of natural vegetation in the area of study. Comparisons between variation at different patches and non-fragmented surrounding areas will be used to estimate the effect of fragmentation relative to the species basal levels of variation. Because the Baja California Peninsula and its surroundings harbor extraordinary levels of endemism, particularly in reptiles (more than 50% of over 130 species), and mammal species (some 20 endemic rodent species), we will include several species in our comparisons. Many of the endemic forms share some common characteristics derived of their moderate or extreme degree of isolation, such as having evolved in-situ, usually through founder effects, and present restricted distributions and dispersion, and, sometimes, low local abundances. All these events together can contribute to an overall depletion of genetic variation on endemic species, which in turn could make them more vulnerable to a further loss of variation due to habitat fragmentation mediated by human activities. Also, because some of these endemic species evolved relatively recently, few mutations may have accumulated between lineages. To test the hypothesis that fragmentation effects are stronger on endemic vs. non endemic species, and on low dispersal vs. highly mobile species, we have contrasted pairs of species from two different vertebrate groups (reptiles and mammals). We include an endemic species of low mobility, besides a high dispersal, widely distributed and closely related species, which will serve as within group controls.