Ferris Kathleen G, Barnett Laryssa L, Blackman Benjamin K, Willis John H
Department of Biology, Duke University, 125 Science Drive, Durham, NC, 27705, USA.
Department of Biology, University of Virginia, 485 McCormick Road, Charlottesville, VA, 22904, USA.
Mol Ecol. 2017 Jan;26(1):208-224. doi: 10.1111/mec.13763. Epub 2016 Aug 26.
The genetic architecture of local adaptation has been of central interest to evolutionary biologists since the modern synthesis. In addition to classic theory on the effect size of adaptive mutations by Fisher, Kimura and Orr, recent theory addresses the genetic architecture of local adaptation in the face of ongoing gene flow. This theory predicts that with substantial gene flow between populations local adaptation should proceed primarily through mutations of large effect or tightly linked clusters of smaller effect loci. In this study, we investigate the genetic architecture of divergence in flowering time, mating system-related traits, and leaf shape between Mimulus laciniatus and a sympatric population of its close relative M. guttatus. These three traits are probably involved in M. laciniatus' adaptation to a dry, exposed granite outcrop environment. Flowering time and mating system differences are also reproductive isolating barriers making them 'magic traits'. Phenotypic hybrids in this population provide evidence of recent gene flow. Using next-generation sequencing, we generate dense SNP markers across the genome and map quantitative trait loci (QTLs) involved in flowering time, flower size and leaf shape. We find that interspecific divergence in all three traits is due to few QTL of large effect including a highly pleiotropic QTL on chromosome 8. This QTL region contains the pleiotropic candidate gene TCP4 and is involved in ecologically important phenotypes in other Mimulus species. Our results are consistent with theory, indicating that local adaptation and reproductive isolation with gene flow should be due to few loci with large and pleiotropic effects.
自现代综合进化论以来，局部适应性的遗传结构一直是进化生物学家关注的核心问题。除了费希尔、木村和奥尔关于适应性突变效应大小的经典理论外，最近的理论还探讨了在持续基因流情况下局部适应性的遗传结构。该理论预测，在种群间存在大量基因流的情况下，局部适应性应主要通过大效应突变或紧密连锁的小效应基因座簇来实现。在本研究中，我们调查了裂叶沟酸浆与其近缘种斑点沟酸浆的一个同域种群在开花时间、交配系统相关性状和叶形方面的分化遗传结构。这三个性状可能参与了裂叶沟酸浆对干燥、暴露的花岗岩露头环境的适应。开花时间和交配系统的差异也是生殖隔离障碍，使其成为“神奇性状”。该种群中的表型杂种为近期基因流提供了证据。利用下一代测序技术，我们在全基因组中生成了密集的单核苷酸多态性（SNP）标记，并绘制了涉及开花时间、花大小和叶形的数量性状基因座（QTL）图谱。我们发现，所有这三个性状的种间分化都归因于少数几个大效应QTL，包括8号染色体上一个高度多效的QTL。这个QTL区域包含多效候选基因TCP4，并参与了其他沟酸浆属物种中具有重要生态意义的表型。我们的结果与理论一致，表明在有基因流的情况下，局部适应性和生殖隔离应归因于少数几个具有大效应和多效性的基因座。
