Gould Matthew J, Cain James W, Atwood Todd C, Harding Larisa E, Johnson Heather E, Onorato Dave P, Winslow Frederic S, Roemer Gary W
Department of Fish, Wildlife and Conservation Ecology New Mexico State University Las Cruces New Mexico USA.
Department of Biology New Mexico State University Las Cruces New Mexico USA.
Ecol Evol. 2022 Oct 10;12(10):e9406. doi: 10.1002/ece3.9406. eCollection 2022 Oct.
The phylogeography of the American black bear () is characterized by isolation into glacial refugia, followed by population expansion and genetic admixture. Anthropogenic activities, including overharvest, habitat loss, and transportation infrastructure, have also influenced their landscape genetic structure. We describe the genetic structure of the American black bear in the American Southwest and northern Mexico and investigate how prehistoric and contemporary forces shaped genetic structure and influenced gene flow. Using a suite of microsatellites and a sample of 550 bears, we identified 14 subpopulations organized hierarchically following the distribution of ecoregions and mountain ranges containing black bear habitat. The pattern of subdivision we observed is more likely a product of postglacial habitat fragmentation during the Pleistocene and Holocene, rather than a consequence of contemporary anthropogenic barriers to movement during the Anthropocene. We used linear mixed-effects models to quantify the relationship between landscape resistance and genetic distance among individuals, which indicated that both isolation by resistance and geographic distance govern gene flow. Gene flow was highest among subpopulations occupying large tracts of contiguous habitat, was reduced among subpopulations in the Madrean Sky Island Archipelago, where montane habitat exists within a lowland matrix of arid lands, and was essentially nonexistent between two isolated subpopulations. We found significant asymmetric gene flow supporting the hypothesis that bears expanded northward from a Pleistocene refugium located in the American Southwest and northern Mexico and that major highways were not yet affecting gene flow. The potential vulnerability of the species to climate change, transportation infrastructure, and the US-Mexico border wall highlights conservation challenges and opportunities for binational collaboration.
美洲黑熊（）的系统地理学特征是隔离在冰川避难所，随后种群扩张和基因混合。包括过度捕猎、栖息地丧失和交通基础设施在内的人为活动也影响了它们的景观遗传结构。我们描述了美国西南部和墨西哥北部美洲黑熊的遗传结构，并研究了史前和当代力量如何塑造遗传结构并影响基因流动。使用一组微卫星和550只熊的样本，我们确定了14个亚种群，这些亚种群按照包含黑熊栖息地的生态区域和山脉分布进行分层组织。我们观察到的细分模式更可能是更新世和全新世期间冰后期栖息地破碎化的产物，而不是人类世期间当代人为移动障碍的结果。我们使用线性混合效应模型来量化个体间景观抗性与遗传距离之间的关系，这表明抗性隔离和地理距离都控制着基因流动。在占据大片连续栖息地的亚种群之间基因流动最高，在马德雷天空岛群岛的亚种群之间基因流动减少，那里山地栖息地存在于干旱土地的低地基质中，而在两个孤立的亚种群之间基本上不存在基因流动。我们发现了显著的不对称基因流动，支持了黑熊从位于美国西南部和墨西哥北部的更新世避难所向北扩张且主要高速公路尚未影响基因流动的假设。该物种对气候变化、交通基础设施和美墨边境墙的潜在脆弱性凸显了保护挑战以及双边合作的机遇。
