Reconciling molecules and morphology in North American Martes

Molecular investigations recently resurrected the Pacific marten (Martes caurina) as a species distinct from the American pine marten (M. americana). Previously, 2 hybrid zones for these species were identified, 1 in the northern Rocky Mountains and another on Kuiu Island off the coast of Southeast Alaska. We test the molecular perspectives on species status and hybridization using geometric morphometrics to characterize Size and shape differences between North American marten species from 6 genetically defined populations: M. americana from interior Alaska, insular M. caurina from Admiralty Island in Southeast Alaska, M. caurina from Colorado, the 2 previously identified hybrid populations, and a third suspected hybrid population on neighboring Kupreanof Island. We found significant differences in shape supporting the designation of 2 morphological species, with M. caurina exhibiting a broader cranial shape and shorter rostrum. We also found significant size differences between species, and also between insular and mainland populations of M. caurina. Morphological intergradation of M. americana and M. caurina in both insular and mainland hybrid zones identified potentially admixed individuals in 2 of the 3 examined contact zones. Under the general lineage concept, our results support species-level classification of both M. americana and M. caurina and suggest that hybridization is geographically limited in scope or may not be effectively detected with morphometrics.