Differential dispersal shapes population structure and patterns of genetic differentiation in two sympatric pond breeding salamanders

Understanding patterns of dispersal, gene flow, and population differentiation are critical to making informed management and conservation decisions. By assessing these processes in multiple sympatric species, we can increase the generality and applicability of management plans. In this study, we assess patterns of genetic differentiation and population structure in two ecologically similar ambystomatid salamanders in Missouri, USA. Ambystoma annulatum (ringed salamander) and A. maculatum (spotted salamander) are both dependent upon forested habitats and fishless ponds for reproduction, but differ in their breeding phenology. In comparing these species, we assessed the support for five different processes that we hypothesized to affect genetic differentiation: (1) resistance of landscape features to movement, (2) distribution of breeding habitat, (3) dispersal propensity, (4) dispersal ability, and (5) breeding habitat quality. Of these hypotheses, we found support for differences in dispersal ability and propensity. In both species, there was a strong pattern of isolation-by-distance. However, A. annulatum exhibited greater overall differentiation ( ), had a greater rate of differentiation increase with distance, and were grouped into three spatially congruent genetic clusters. In contrast, A. maculatum consisted of a single population cluster and overall was 0.047. We estimated the mean genetic dispersal distance of A. annulatum and A. maculatum to be 1,693 m and 2,050 m, respectively. Our results underscore the importance of considering multiple species when developing management criteria to better account for differences in dispersal ability.