Continental-Scale Variability in Climate History Since the Last Glacial Maximum Provides A Natural Experiment for the Influence of Climate On Duck Distributions (Genus Anas)

Climate change can alter the availability of suitable habitat and, thus, the fate and evolution of species. Climate does not lend itself to experimental manipulation over continental scales but natural variability in climate histories among continents provide the opportunity for comparative studies of responses of globally distributed taxonomic groups to climate change. Here we provide a test of the continental-scale variability in the response to climate change of ducks from the genus Anas over the last 21,000 years. We developed distribution models of the breeding ranges of 33 Anas species (including representatives from all inhabited continents) and used them to hindcast duck distributions to the Last Glacial Maximum (LGM ~21k years BP). We used the software MAXENT and presence-only data from multiple public and private sources (including GBIF and ORNIS) paired with temperature and precipitation data (WorldClim and PMIP2). In an effort to correct for a strong North American bias in the available data on duck breeding localities, we (1) geographically sub-sampled the presence data, and (2) adjusted the concentration of pseudo-absences (environmental background data) to sampling effort. We validated our models through (a) held-out data, and (b) comparisons to published ranges (NatureServe, GROMS). The models’ power to predict geographic ranges of sister species on different continents provided an additional indication of their biological validity.