Data from: The eastern migratory caribou: the role of genetic introgression in ecotype evolution

Understanding the evolutionary history of contemporary animal groups is essential for conservation and management of endangered species like caribou (Rangifer tarandus). In central Canada, the ranges of two caribou subspecies (barren-ground/ woodland caribou) and two woodland caribou ecotypes (boreal/ eastern migratory) overlap. Our objectives were to reconstruct the evolutionary history of the eastern migratory ecotype and to assess the potential role of introgression in ecotype evolution. STRUCTURE analyses identified five higher-order groups (i. e. three boreal caribou populations, eastern migratory ecotype, and barren-ground). The evolutionary history of the eastern migratory ecotype was best explained by an early genetic introgression from barren-ground into a woodland caribou lineage during the late Pleistocene and subsequent divergence of the eastern migratory ecotype during the Holocene. These results are consistent with the retreat of the Laurentide ice sheet and the colonization of the Hudson Bay coastal areas subsequent to the establishment of forest tundra vegetation ~7,000 years ago. This historical reconstruction of the eastern migratory ecotype further supports its current classification as a conservation unit, specifically a Designatable Unit, under Canada’s Species at Risk Act. These findings have implications for other sub-specific contact zones for caribou and other North American species in conservation unit delineation.阐明现代动物类群的演化历史，对于驯鹿（Rangifer tarandus）等濒危物种的保护与管理至关重要。在加拿大中部区域，两种驯鹿亚种——苔原驯鹿（barren-ground caribou）与林地驯鹿（woodland caribou），以及两种林地驯鹿生态型——北方林型（boreal）与东部迁徙型（eastern migratory）的分布范围存在重叠。本研究旨在重建东部迁徙型生态型的演化历史，并评估基因渐渗（introgression）在该生态型演化进程中的潜在作用。STRUCTURE群体结构分析鉴定出5个高阶类群，即3个北方林型驯鹿种群、东部迁徙型生态型与苔原驯鹿。东部迁徙型生态型的演化历史可得到最合理解释：更新世晚期，苔原驯鹿向某一林地驯鹿支系发生早期基因渐渗，随后在全新世时期该支系分化形成东部迁徙型生态型。上述结果与劳伦泰德冰盖（Laurentide ice sheet）消退、约7000年前森林苔原植被建立后哈德逊湾沿海区域的物种定居过程相吻合。本次对东部迁徙型生态型的历史重建，进一步支持其在《加拿大濒危物种法》（Species at Risk Act）框架下被归类为保护单元——具体为可指定单元（Designatable Unit）的现行分类。该研究结果对于驯鹿其他亚种接触区以及北美其他物种的保护单元划定工作具有重要参考价值。