Print PagePerennial streams in desert environments occur as highly fragmented habitats. The evolution of freshwater animals restricted to these habitats should be strongly influenced by genetic connectivity— a function of dispersal and the spatial structure of the habitat. In this study, we investigated genetic connectivity among populations of the giant water bug Abedus herberti, a flightless hemipteran. We used molecular genetic data from 10 microsatellite loci to describe spatial patterns in genetic diversity for 10 populations (249 individuals) across the Huachuca and Santa Rita mountain ranges in southeastern Arizona.
Results/Conclusions
Genetic diversity within populations (as measured by expected heterozygosity) was moderately high, ranging from 0.56 to 0.68. Estimates of effective population size ranged from 8 to 70. Genetic diversity and effective population size were not correlated with stream order, suggesting that location within the stream network is not an important population genetic factor in this species. Tests of genetic differentiation between pairs of populations were all significant, which suggests that gene flow among populations is restricted. There was no significant pattern of isolation by distance, indicating that genetic drift due to small population size and habitat fragmentation, rather than gene flow, may be the dominant force contributing to population structure in A. herberti. We found that the 10 populations were partitioned into 3 genetic clusters that largely correspond with the geographic arrangement of the populations in the two mountain ranges. Thus, while phylogeographic affinities are apparent at broad geographic scales, habitat fragmentation maintains strong among-population genetic differentiation at local scales.
