Department of Evolution and Ecology, University of California, Davis, Davis, California.
Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada.
Mol Ecol. 2019 Jun;28(11):2802-2813. doi: 10.1111/mec.15097. Epub 2019 Jun 5.
As humans cause the redistribution of species ranges, hybridization between previously allopatric species is on the rise. Such hybridization can have complex effects on overall fitness of native species as new allelic combinations are tested. Widespread species introductions provide a unique opportunity to study selection on introgressed alleles in independent, replicated populations. We examined selection on alleles that repeatedly introgressed from introduced rainbow trout (Oncorhynchus mykiss) into native westslope cutthroat trout (Oncorhynchus clarkii lewisi) populations in western Canada. We found that the degree of introgression of individual single nucleotide polymorphisms from the invasive species into the native is correlated between independent watersheds. A number of rainbow trout alleles have repeatedly swept to high frequency in native populations, suggesting parallel adaptive advantages. Using simulations, we estimated large selection coefficients up to 0.05 favoring several rainbow trout alleles in the native background. Although previous studies have found reduced hybrid fitness and genome-wide resistance to introgression in westslope cutthroat trout, our results suggest that some introduced genomic regions are strongly favored by selection. Our study demonstrates the utility of replicated introductions as case studies for understanding parallel adaptation and the interactions between selection and introgression across the genome. We suggest that understanding this variation, including consideration of beneficial alleles, can inform management strategies for hybridizing species.
随着人类导致物种分布范围的重新分配，以前处于地理隔离状态的物种之间的杂交现象正在增加。这种杂交可能会对本地物种的整体适应性产生复杂的影响，因为新的等位基因组合正在被测试。广泛的物种引入为在独立的、重复的种群中研究渐渗等位基因的选择提供了一个独特的机会。我们研究了从引入的虹鳟鱼（Oncorhynchus mykiss）反复渐渗到加拿大西部本地西部山溪红点鲑（Oncorhynchus clarkii lewisi）种群的等位基因的选择。我们发现，从入侵物种到本地的单个核苷酸多态性的渐渗程度在独立的流域之间存在相关性。一些虹鳟鱼等位基因在本地种群中反复迅速达到高频，表明存在平行的适应性优势。通过模拟，我们估计了高达 0.05 的较大选择系数，有利于本地背景下的几个虹鳟鱼等位基因。尽管之前的研究发现，西部山溪红点鲑的杂种适应性降低，且对渐渗有全基因组的抗性，但我们的研究结果表明，一些引入的基因组区域受到选择的强烈青睐。我们的研究表明，重复引入可以作为案例研究，用于理解平行适应性以及基因组范围内选择和渐渗之间的相互作用。我们建议，了解这种变异，包括有益等位基因的考虑，可以为杂交物种的管理策略提供信息。
