McLaughlin Jessica F, Faircloth Brant C, Glenn Travis C, Winker Kevin
University of Alaska Museum, Fairbanks, AK, USA.
Sam Noble Oklahoma Museum of Natural History, Norman, OK, USA.
Mol Ecol. 2020 Sep;29(18):3526-3542. doi: 10.1111/mec.15574. Epub 2020 Sep 2.
Determining how genetic diversity is structured between populations that span the divergence continuum from populations to biological species is key to understanding the generation and maintenance of biodiversity. We investigated genetic divergence and gene flow in eight lineages of birds with a trans-Beringian distribution, where Asian and North American populations have likely been split and reunited through multiple Pleistocene glacial cycles. Our study transects the speciation process, including eight pairwise comparisons in three orders (ducks, shorebirds and passerines) at population, subspecies and species levels. Using ultraconserved elements (UCEs), we found that these lineages represent conditions from slightly differentiated populations to full biological species. Although allopatric speciation is considered the predominant mode of divergence in birds, all of our best divergence models included gene flow, supporting speciation with gene flow as the predominant mode in Beringia. In our eight lineages, three were best described by a split-migration model (divergence with gene flow), three best fit a secondary contact scenario (isolation followed by gene flow), and two showed support for both models. The lineages were not evenly distributed across a divergence space defined by gene flow (M) and differentiation (F ), instead forming two discontinuous groups: one with relatively shallow divergence, no fixed single nucleotide polymorphisms (SNPs), and high rates of gene flow between populations; and the second with relatively deeply divergent lineages, multiple fixed SNPs, and low gene flow. Our results highlight the important role that gene flow plays in avian divergence in Beringia.
确定跨越从种群到生物物种的分化连续体的种群之间的遗传多样性是如何构建的，是理解生物多样性的产生和维持的关键。我们研究了具有跨白令海分布的八个鸟类谱系中的遗传分化和基因流，在这种分布中，亚洲和北美种群可能在多个更新世冰川周期中被分裂并重新聚合。我们的研究贯穿了物种形成过程，包括在种群、亚种和物种水平上对三个目（鸭类、滨鸟和雀形目）进行的八对比较。使用超保守元件（UCEs），我们发现这些谱系代表了从略有分化的种群到完全生物物种的各种情况。尽管异域物种形成被认为是鸟类分化的主要模式，但我们所有最佳的分化模型都包括基因流，支持以基因流作为白令地区主要模式的物种形成。在我们的八个谱系中，三个谱系最适合用分裂迁移模型（伴随基因流的分化）来描述，三个谱系最符合二次接触情景（隔离后伴随基因流），还有两个谱系对这两种模型都有支持。这些谱系在由基因流（M）和分化（F）定义的分化空间中分布不均，而是形成了两个不连续的组：一组具有相对较浅的分化、没有固定的单核苷酸多态性（SNP），且种群间基因流率高；另一组具有分化程度相对较深的谱系、多个固定的SNP，且基因流低。我们的结果突出了基因流在白令地区鸟类分化中所起的重要作用。
