DISTRIBUTION MODELING OF BEAVERS (RODENTIA: CASTORIDAE) IN NORTH AMERICA: PROJECTING SPECIES DISTRIBUTION FROM THE PLIOCENE M2 TO THE FUTURE

Beavers (genus Castor) have been present in North America since the late Miocene, around 7 million years ago. Little is known about the dispersal of Castor from Eurasia and its spread across North America. The purpose of this study is to use species occurrence data along with bioclimatic variables to create models projecting the past, present, and future potential distributions and habitat suitability of Castor across North America. Specimen occurrence data for Castor canadensis were downloaded from the Global Biodiversity Information Facility (GBIF), modern bioclimatic data (1970-2000 CE), and future bioclimatic variables (2081-2100 for shared socioeconomic pathway (SSP) 3-7.0) were downloaded from WorldClim. Past climatic variables for the Pliocene M2, Pleistocene Last Interglacial, and Pleistocene Last Glacial Maximum were downloaded from PaleoClim. Fossil locality data for Miocene-Pliocene C. californicus and Pleistocene C. canadensis occurrences were used as validation points for the projection models. Models were developed using Maximum Entropy (MaxEnt). The models showed distinct shifts in habitat suitability from the Pliocene to the present. Fossil occurrences of both C. californicus and C. canadensis fell within suitable habitat ranges predicted in the distribution models. This suggests that the environmental requirements and distributions of C. californicus were like those of C. canadensis, as would be expected given the strong morphological similarity between the two taxa.