Genetic structure of endangered Stephens' kangaroo rat populations in southern California

摘要

Stephens' kangaroo rat (Dipodomys stephensi) was listed as an endangered species in 1988 due to significant loss of its habitat through agricultural and urban development. We examined allozyme variation in 245 individuals from 10 locations in Riverside and San Diego counties, California, to assess the genetic consequences of habitat fragmentation. Populations were polymorphic at 0.050 to 0.175 of the loci surveyed (mean P = 0.125), and mean heterozygosities varied from 0.005 to 0.032 (mean H = 0.019). Despite low levels of genetic diversity within populations, significant F-ST values were observed at 5 of 10 polymorphic loci (mean F-ST = 0.266), indicating population differentiation. Genetic distances for individual loci and across all loci were not significantly correlated with geographic distances. The patterns of genetic diversity observed suggest that habitat fragmentation has influenced population genetic structure in this species. Genetic drift and restricted gene flow stemming from the fragmentation of once contiguous populations into isolated populations are suggested as contributing factors. Demographic data suggest that periodic bottlenecks in population size may also contribute to these patterns.