Wooding S, Ward R
Department of Biology, University of Utah, USA.
Mol Biol Evol. 1997 Nov;14(11):1096-105. doi: 10.1093/oxfordjournals.molbev.a025719.
To determine the extent of phylogeographic structuring in North American black bear (Ursus americanus) populations, we examined mitochondrial DNA sequences (n = 118) and restriction fragment length polymorphism profiles (n = 258) in individuals from 16 localities. Among the bears examined, 19 lineages falling into two highly divergent clades were identified. The clades differ at 5.0% of nucleotide positions, a distance consistent with an origin 1.8 MYA, and have different but overlapping geographical distributions. Areas of clade cooccurrence show that eastern and western populations are currently mixing, but regional differences in lineage distribution suggest that mixing has begun only recently. The long-term population history of black bears appears to be characterized predominantly by long-term regional isolation followed by recent contact and hybridization. Congruence between the pattern of diversity observed in black bears and patterns of forest refuge formation during the Pleistocene supports earlier speculation that Pleistocene forest fragmentations underlie a common pattern in the phylogeography of North American forest taxa.
为了确定北美黑熊（美洲黑熊）种群的系统地理学结构程度，我们检测了来自16个地点的个体的线粒体DNA序列（n = 118）和限制性片段长度多态性图谱（n = 258）。在所检测的熊中，鉴定出了19个谱系，它们分属于两个高度分化的进化枝。这两个进化枝在5.0%的核苷酸位置上存在差异，这种差异程度与180万年前的起源一致，并且它们具有不同但重叠的地理分布。进化枝共存的区域表明东部和西部种群目前正在混合，但谱系分布的区域差异表明混合只是最近才开始的。黑熊长期的种群历史似乎主要以长期的区域隔离为特征，随后是最近的接触和杂交。在黑熊中观察到的多样性模式与更新世期间森林避难所形成模式之间的一致性，支持了早期的推测，即更新世森林破碎化是北美森林类群系统地理学中一种常见模式的基础。
