| Summary: | Pleistocene refugia likely contributed to the modern biodiversity of northern areas. Using the mitochondrial DNA cytochrome-b gene, we compared 11 forest-dwelling bird species from Haida Gwaii (formerly the Queen Charlotte Islands) with populations from Alaska, Washington, and other locations in the United States. If Haida Gwaii was an unglaciated refugium, its modern populations should feature a high number of endemic lineages and divergence times that predate the end of the last glacial maximum, ca. 13,000–19,000 years before present (ybp). Furthermore, the genetic diversity of these populations should be higher than that in areas colonized after the glacial retreat. Four of the species examined from Haida Gwaii showed old divergences and a high percentage of endemic lineages: the Northern Saw-whet Owl (Aegolius acadicus), Hairy Woodpecker (Picoides villosus), Steller's Jay (Cyanocitta stelleri), and Pine Grosbeak (Pinícola enucleator); all four have endemic subspecies on these islands. The Pacific Wren (Troglodytes pacificus) and Song Sparrow (Melospiza melodia) showed genetic trends associated with populations in refugia, including high genetic diversity on Haida Gwaii. Estimated divergence dates of these six species were fairly uniform (∼20,000–30,000 ybp), being greatest for the Hairy Woodpecker (>70,000 ybp) and Pine Grosbeak (>120,000 ybp). There was an association between apparent occurrence in a refugium and a sedentary lifehistory strategy and a trend for endemic subspecies (4 of 6) also to show this association. Our findings suggest that the Haida Gwaii area hosted a forested refugium during the cycles of climatic change in the late Pleistocene.
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