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

Area of Science:

• Genetics
• Evolutionary Biology
• Quaternary Science

Background:

• The Haida Gwaii archipelago's role as a glacial refugium is debated.
• Morphological differences in endemic black bears suggest isolation, but this can occur postglacially.
• Previous studies have discussed the potential for a refugium on the northwestern coast of North America.

Purpose of the Study:

• To investigate the phylogenetic distinctiveness of Haida Gwaii black bears (Ursus americanus).
• To determine if observed morphological differences reflect ancient isolation or postglacial divergence.
• To assess the evidence for a glacial refugium on the continental shelf of British Columbia.

Main Methods:

• Phylogenetic analysis of cytochrome b gene sequences (719 bp) from Haida Gwaii black bears.
• Comparison of sequences with conspecific black bears from northwestern North America.
• Analysis of genetic divergence and synapomorphies between coastal and continental populations.

Main Results:

• Haida Gwaii black bears are genetically indistinguishable from coastal British Columbia and Vancouver Island bears.
• Coastal and continental bears exhibit significant genetic divergence (3.6% sequence divergence, 24 synapomorphies).
• A distinct coastal mitochondrial lineage is present across recognized coastal subspecies, suggesting postglacial differentiation.

Conclusions:

• Morphological differences in black bear subspecies are likely postglacially derived, not indicative of long-term isolation on Haida Gwaii.
• The findings support the hypothesis of a submerged glacial refugium connecting Haida Gwaii, Vancouver Island, and the mainland coast.
• This refugium likely served as a crucial source for postglacial recolonization of northwestern North America.