Cryptic population structure in sandhill cranes (Antigone canadensis) of the Pacific Flyway

Population segregation catalyzes genetic differentiation and can lead to speciation. Population genetic structure is also critically important for population management, especially in species characterized by small, isolated populations. Sandhill Crane (Antigone canadensis) populations of the Pacific Flyway are made up of breeding populations nesting west of the Rocky Mountains, and isolated by intermediate mountain ranges. Current management policy in British Columbia treats all Sandhill Cranes as a single population, whereas in the western United States subpopulations are subject to population specific management. Here, we analyze microsatellite markers, mitochondrial DNA sequences, and mitochondrial haplogroups, derived from 203 individual Sandhill Cranes to elucidate population genetic structure of cranes migrating along the Pacific Flyway to summer breeding habitat on the North and Central Coast of British Columbia and southeast Alaska. STRUCTURE, AMOVA, FST, DAPC, and phylogenetic analyses reveal that geographically separated crane populations along the west coast of North America show substantial genetic differentiation in the Pacific Flyway. These findings are consistent with behavioural and ecological evidence - divergent diets, flyways and breeding habitats. We conclude that the relatively small coastal Sandhill Crane populations deserve special management consideration to safeguard their genetic diversity and adaptations, and to mitigate deleterious impacts of current and future climate change scenarios.

种群隔离能够推动遗传分化，甚至可能引发物种形成。种群遗传结构对种群管理至关重要，对于种群规模偏小且呈隔离状态的物种尤为关键。太平洋迁飞区（Pacific Flyway）内的沙丘鹤（Sandhill Crane，Antigone canadensis）种群，由落基山脉以西的筑巢繁殖种群构成，且被中间山脉所隔离。不列颠哥伦比亚省（British Columbia）当前的管理政策将所有沙丘鹤视为单一种群，而美国西部的沙丘鹤亚种群则实施种群特异性管理。本研究对203只个体沙丘鹤的微卫星标记（microsatellite markers）、线粒体DNA序列（mitochondrial DNA sequences）以及线粒体单倍型类群（mitochondrial haplogroups）进行分析，旨在阐明沿太平洋迁飞区迁徙、前往不列颠哥伦比亚省北海岸、中海岸以及阿拉斯加东南部夏季繁殖栖息地的沙丘鹤种群遗传结构。STRUCTURE、AMOVA、FST、DAPC及系统发育分析结果显示，北美西海岸地理隔离的鹤类种群在太平洋迁飞区内存在显著的遗传分化。该研究结果与行为学及生态学证据相契合，即这些种群存在不同的食性、迁飞通道与繁殖栖息地。综上，本研究认为规模相对较小的沿海沙丘鹤种群应获得特殊的管理关注，以保护其遗传多样性与适应性，并缓解当前及未来气候变化情景所带来的不利影响。