Understanding the demographic response of species to environmental change is critical in ecology, evolution, and conservation biology, but historical records of population history are rarely available. Surveying genetic variation can potentially provide an effective alternative to census-based estimates of population size, yielding insight into the demographic history of a population, including migration events, population structure, expansions, and bottlenecks. However, to assess performance of these methods it is important to compare these genetic estimates of population history to known demography. Here, we leveraged temporal genomic data from a well-studied natural wetland community with 37 years of mark-recapture data to perform demographic inference on species with documented population declines (A. talpoideum) and expansions (A. opacum) in response to climate driven change in wetland hydroperiod. We used double-digest restriction-site associated DNA (ddRAD) sequencing to generate SNP data sets from temporally sampled populations of A. opacum and A. talpoideum and used coalescent-based demographic inference to compare alternate evolutionary models that account for population growth or decline.
Results/Conclusions
For both species, coalescent-based demographic model inference supported population size changes that conformed to mark-recapture field data. Parameter estimation in A. talpoideum resulted in tight confidence intervals, and was robust to our variations in analytical approach. However, parameter estimation for A. opacum resulted in highly inconsistent values, tempering our confidence in detecting a demographic trend in this species. Overall, our results demonstrate the potential utility of demographic inference on an ecological scale, but indicate that the method may work for some systems and evolutionary scenarios, but not others. Our study complements a larger body of work at this long-term study site, Rainbow Bay, which has provided unprecedented insight into amphibian population dynamics.