Chavarria-Pizarro Tania, Gomez Juan Pablo, Ungvari-Martin Judit, Bay Rachael, Miyamoto Michael M, Kimball Rebecca
Department of Biology University of Florida Gainesville FL USA.
Department of Biology Ludwig Maximilian University of Munich Munich Germany.
Ecol Evol. 2019 Nov 19;9(24):13902-13918. doi: 10.1002/ece3.5826. eCollection 2019 Dec.
Despite the enormous advances in genetics, links between phenotypes and genotypes have been made for only a few nonmodel organisms. However, such links can be essential to understand mechanisms of ecological speciation. The Costa Rican endemic Mangrove Warbler subspecies provides an excellent subject to study differentiation with gene flow, as it is distributed along a strong precipitation gradient on the Pacific coast with no strong geographic barriers to isolate populations. Mangrove Warbler populations could be subject to divergent selection driven by precipitation, which influences soil salinity levels, which in turn influences forest structure and food resources. We used single nucleotide polymorphisms (SNPs) and morphological traits to examine the balance between neutral genetic and phenotypic divergence to determine whether selection has acted on traits and genes with functions related to specific environmental variables. We present evidence showing: (a) associations between environmental variables and SNPs, identifying candidate genes related to bill morphology (BMP) and osmoregulation, (b) absence of population genetic structure in neutrally evolving markers, (c) divergence in bill size across the precipitation gradient, and (d) strong phenotypic differentiation ( ) which largely exceeds neutral genetic differentiation ( ) in bill size. Our results indicate an important role for salinity, forest structure, and resource availability in maintaining phenotypic divergence of Mangrove Warblers through natural selection. Our findings add to the growing body of literature identifying the processes involved in phenotypic differentiation along environmental gradients in the face of gene flow.
尽管遗传学取得了巨大进展，但仅在少数非模式生物中建立了表型与基因型之间的联系。然而，这种联系对于理解生态物种形成的机制可能至关重要。哥斯达黎加特有的红树林莺亚种是研究基因流导致分化的绝佳对象，因为它沿着太平洋海岸的强降水梯度分布，没有强大的地理屏障来隔离种群。红树林莺种群可能受到降水驱动的趋异选择，降水会影响土壤盐分水平，进而影响森林结构和食物资源。我们使用单核苷酸多态性（SNP）和形态特征来检验中性遗传分化与表型分化之间的平衡，以确定选择是否作用于与特定环境变量相关的性状和基因。我们提供的证据表明：（a）环境变量与SNP之间存在关联，并确定了与喙形态（骨形态发生蛋白，BMP）和渗透调节相关的候选基因；（b）在中性进化标记中不存在种群遗传结构；（c）喙大小在降水梯度上存在差异；（d）在喙大小方面，强烈的表型分化（ ）在很大程度上超过了中性遗传分化（ ）。我们的结果表明，盐度、森林结构和资源可用性在通过自然选择维持红树林莺的表型分化方面发挥着重要作用。我们的发现为越来越多的文献增添了内容，这些文献确定了在基因流存在的情况下，沿环境梯度进行表型分化所涉及的过程。
