Department of Botany and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, Canada.
School of Environmental and Rural Science, University of New England, Armidale, NSW, Australia.
Mol Ecol. 2020 Jul;29(14):2535-2549. doi: 10.1111/mec.15428. Epub 2020 Apr 24.
Both models and case studies suggest that chromosomal inversions can facilitate adaptation and speciation in the presence of gene flow by suppressing recombination between locally adapted alleles. Until recently, however, it has been laborious and time-consuming to identify and genotype inversions in natural populations. Here we apply RAD sequencing data and newly developed population genomic approaches to identify putative inversions that differentiate a sand dune ecotype of the prairie sunflower (Helianthus petiolaris) from populations found on the adjacent sand sheet. We detected seven large genomic regions that exhibit a different population structure than the rest of the genome and that vary in frequency between dune and nondune populations. These regions also show high linkage disequilibrium and high heterozygosity between, but not within, arrangements, consistent with the behaviour of large inversions, an inference subsequently validated in part by comparative genetic mapping. Genome-environment association analyses show that key environmental variables, including vegetation cover and soil nitrogen, are significantly associated with inversions. The inversions colocate with previously described "islands of differentiation," and appear to play an important role in adaptive divergence and incipient speciation within H. petiolaris.
两种模式和案例研究表明，染色体倒位可以通过抑制局部适应等位基因之间的重组，促进有基因流动存在时的适应和物种形成。然而，直到最近，在自然种群中识别和分型倒位仍然是费力和耗时的。在这里，我们应用 RAD 测序数据和新开发的群体基因组学方法，鉴定出区分草原向日葵（Helianthus petiolaris）沙丘生态型和相邻沙片中发现的种群的可能倒位。我们检测到七个大的基因组区域，这些区域的群体结构与基因组的其余部分不同，并且在沙丘和非沙丘种群之间的频率不同。这些区域之间还表现出高连锁不平衡和高杂合性，但在排列内不存在，这与大倒位的行为一致，这一推断随后通过比较遗传作图得到了部分验证。全基因组环境关联分析表明，关键环境变量，包括植被覆盖和土壤氮，与倒位显著相关。这些倒位与之前描述的“分化岛”共定位，并且似乎在 H. petiolaris 内的适应性分歧和初始物种形成中发挥重要作用。
