A MULTILOCUS PHYLOGENY OF THE HOLARCTIC GROUND SQUIRREL, GENUS UROCITELLUS
Donavan Jackson Sr.1, Bryan McLean1, Joe Cook2.
1University of New Mexico, Albuquerque, NM, 2Museum of Southwestern Biology, University of New Mexico, Albuquerque, NM.
Squirrels (family Sciuridae) form a cosmopolitan group that colonized a range of habitats and environments. Within the Sciuridae, Holarctic ground squirrels (Urocitellus) comprise a genus found predominantly in higher latitudes and altitudes of North America and Asia, including Alaska, Canada, and Siberia. However, despite decades of research on both the biogeography and socioecology of the group, the evolutionary relationships of the 12 species within the genus are poorly defined. In addition, the timing of colonization of the high-Arctic by 2 species, U. undulatus and U. parryii, remains unresolved. To better understand the phylogeny of Urocitellus and the number of Arctic colonizations, we used multilocus DNA sequence data (1 mitochondrial and 4 nuclear genes) and Bayesian species tree reconstruction. Despite some gene tree discordance, preliminary results suggest the Arctic was colonized twice. These independent events reflect the high adaptability of squirrels. Future research directions include sequencing additional loci and performing ancestral range reconstruction to more fully understand the evolutionary and biogeographic history of Holarctic ground squirrels and provide a rigorous temporal and spatial framework for future studies of adaptation in this diverse group.