Widely separated populations of Culex erythrothorax (Culicidae) are not genetically differentiated

Many mosquitoes that are prominent disease vectors and human pests disperse widely and show genetic similarities over hundreds or thousands of kilometers. The importance of local geographic features (e.g., mountains, large bodies of water, elevation) vary widely among species that have been studied to date. The tule mosquito Culex erythrothorax, a common pest in San Diego County, is thought to have low dispersal abilities relative to other mosquito species. The presence of larvae only in specific types of emergent vegetation results in discontinuous population distributions. Thus, one would expect this species to be subdivided into gene pools at the level of the watershed or lower. We collected C.erythrothorax from 25 sampling sites across San Diego County, California, spanning six watersheds and 70km. Using mitochondrial DNA sequence data and ten novel microsatellite markers, we found little to no population structure across the study area. We consider the relative importance of high gene flow and population history in shaping these current patterns of genetic differentiation.