Byun S A, Koop B F, Reimchen T E
Department of Biology, P.O. Box 3020, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada.
Center for Environmental Health, P.O. Box 3020, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada.
Evolution. 1997 Oct;51(5):1647-1653. doi: 10.1111/j.1558-5646.1997.tb01487.x.
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.
海达瓜依（夏洛特皇后群岛）作为北美西北海岸生物避难所这一颇具争议的角色，在五十多年里一直被广泛讨论。海达瓜依存在形态上有差异的亚种，这是表明该群岛在威斯康星期间作为避难所角色的主要证据之一。然而，由于形态差异既可能在冰期后产生，也可能在长期隔离中出现，所以这样的证据并不明确。为了研究这个问题，我们对海达瓜依特有的黑熊（美洲黑熊）细胞色素b序列（719碱基对）进行了系统发育分析，并将其与来自北美各地的同种个体进行比较，主要聚焦于西北海岸。我们发现，海达瓜依的熊与不列颠哥伦比亚和温哥华岛的沿海熊没有区别，但与大陆熊有很大不同。沿海熊和大陆熊有24个共同衍征，平均序列差异为3.6%。沿海线粒体谱系存在于三个公认的沿海亚种中，这表明区分这些分类群的形态特征可能是冰期后形成的。这些数据与最近的观点一致，即现在被淹没的大陆架上存在一个冰川避难所，它连接着海达瓜依、温哥华岛和不列颠哥伦比亚大陆的沿海边缘。这个避难所本可以成为北美西北部冰期后重新殖民的另一个来源。
