Ancient hybridization and an Irish origin for the modern polar bear matriline.
Ancient hybridization and an Irish origin for the modern polar bear matriline.
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DOI：
10.1016/j.cub.2011.05.058
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发表时间：
2011-08-09
期刊：
影响因子：
--
通讯作者：
Shapiro B
中科院分区：
文献类型：
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作者：
Edwards CJ;Suchard MA;Lemey P;Welch JJ;Barnes I;Fulton TL;Barnett R;O'Connell TC;Coxon P;Monaghan N;Valdiosera CE;Lorenzen ED;Willerslev E;Baryshnikov GF;Rambaut A;Thomas MG;Bradley DG;Shapiro B
北极熊（Ursus maritimus）是最易受北极气候快速变化影响的物种之一，它们的生存受到全球关注。尽管如此，人们对北极熊的物种历史知之甚少。了解基本的进化信息，例如它们从棕熊（U. arctos）最初分化的时间和条件，或者它们对以往环境变化的反应，将对未来的保护策略大有裨益。
我们使用了一个空间明确的系统发生地理模型，对过去12万年中在其当前和过去地理范围内采集的242条棕熊和北极熊母系的动态进行了估计。我们的研究结果表明，这些母系的当前分布是由区域稳定性以及从冰河时代避难所快速、远距离扩散共同塑造的。此外，在更新世晚期，北极熊和棕熊之间可能发生了多次杂交。
棕熊和北极熊重建的母系历史有两个显著特征。首先，它被剧烈且离散的气候驱动的扩散事件所打断。其次，当这两个物种的分布范围重叠时，它们之间的机会性交配留下了强烈的基因印记。特别是，与已灭绝的爱尔兰棕熊可能发生的基因交流形成了现代北极熊母系的起源。这表明种间杂交可能不仅比以前认为的更为普遍，而且可能是物种在环境恶化时期应对边缘栖息地的一种机制。
Polar bears (Ursus maritimus) are among those species most susceptible to the rapidly changing arctic climate, and their survival is of global concern. Despite this, little is known about polar bear species history. Future conservation strategies would significantly benefit from an understanding of basic evolutionary information, such as the timing and conditions of their initial divergence from brown bears (U. arctos) or their response to previous environmental change. We used a spatially explicit phylogeographic model to estimate the dynamics of 242 brown bear and polar bear matrilines sampled throughout the last 120,000 years and across their present and past geographic ranges. Our results show that the present distribution of these matrilines was shaped by a combination of regional stability and rapid, long-distance dispersal from ice-age refugia. In addition, hybridization between polar bears and brown bears may have occurred multiple times throughout the Late Pleistocene. The reconstructed matrilineal history of brown and polar bears has two striking features. First, it is punctuated by dramatic and discrete climate-driven dispersal events. Second, opportunistic mating between these two species as their ranges overlapped has left a strong genetic imprint. In particular, a likely genetic exchange with extinct Irish brown bears forms the origin of the modern polar bear matriline. This suggests that interspecific hybridization not only may be more common than previously considered but may be a mechanism by which species deal with marginal habitats during periods of environmental deterioration.