NORTH AMERICAN BLACK BEAR mtDNA PHYLOGEOGRAPHY: IMPLICATIONS FOR MORPHOLOGY AND THE HAIDA GWAII GLACIAL REFUGIUM CONTROVERSY.

Abstract

The controversial role of Haida Gwaii (Queen Charlotte Islands) as a biological refugium on the northwestern coast of North America has been widely discussed for more than fifty years. The presence of morphologically divergent subspecies on Haida Gwaii is one of the major lines of evidence suggesting this archipelago's role as a refugium during the Wisconsin. However, since morphological distinction can be derived postglacially as well as in extended isolation, such evidence is ambiguous. To examine this question, we did a phylogenetic analysis of cytochrome b sequences (719 bp) of black bear (Ursus americanus), one of the distinctive endemics of Haida Gwaii, and compared these with conspecifics from across North America, focusing primarily on the northwestern coast. We found that the Haida Gwaii bear are indistinguishable from coastal bear of British Columbia and Vancouver Island, but are highly distinct from continental bear. Coastal and continental bears differ by 24 synapomorphies and an average sequence divergence of 3.6%. The coastal mitochondrial lineage occurs in each of the three recognized coastal subspecies suggesting that the morphological characteristics differentiating these taxa may be postglacially derived. The data are consistent with recent suggestions that a glacial refugium existed on the now submerged continental shelf connecting Haida Gwaii, Vancouver Island, and the coastal fringe of mainland British Columbia. This refugium would have been an additional source for postglacial recolonization of northwestern North America.