Meeting Abstract
Several North American mammals underwent allopatric speciation during the Wisconsin glaciation (11.7 kya). The retreat of these glaciers resulted in faster expansion of Eastern forests than Western, keeping many Western populations isolated and exposing dispersing Eastern populations to a wider range of biomes. Molecular data suggests pine martens were separated into two species, Martes americana and Martes caurina, during this period. Skeletal limb morphology supports this separation; however, limb morphology also correlates with biome. I tested for the evolutionary tempo and mode of skeletal limb morphology in M. americana and M. caurina using 3D geometric morphometric landmark data from limb bones and a Bayesian phylogeny created from the 12S, 16S, cytochrome b, and d-loop sequences. I found that a time dependent evolutionary model, Delta/Independent Evolution, best fits morphological evolution. The evolutionary rates differed, with M. americana from broadleaf forests in the eastern U.S. having the fastest rate and M. caurina having the slowest. Disparate skeletal limb morphology of the two species evolved early in their speciation as a result of glacial isolation during the Pleistocene. Researchers have hypothesized that after glacial retreat M. americana dispersed from a southeastern refugium to most of Canada and Alaska while M. caurina remained restricted to the western US. The faster rate of evolution in M. americana may correlate with its colonization of most of North America, which includes variable biomes. The slower evolutionary rate of M. caurina suggests its morphology represents the ancestral state, but comparison to the extinct noble marten indicates Pleistocene martens were more robust than living.
