Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland.
Divisions of Basic Sciences and Human Biology, Fred Hutchinson Cancer Research Center, Seattle, WA, United States.
Evolution. 2023 Jan 23;77(1):110-122. doi: 10.1093/evolut/qpac025.
Recent studies have shown that the repeated evolution of similar phenotypes in response to similar ecological conditions (here "parallel evolution") often occurs through mutations in the same genes. However, many previous studies have focused on known candidate genes in a limited number of systems. Thus, the question of how often parallel phenotypic evolution is due to parallel genetic changes remains open. Here, we used quantitative trait locus (QTL) mapping in F2 intercrosses between lake and stream threespine stickleback (Gasterosteus aculeatus) from four independent watersheds on Vancouver Island, Canada to determine whether the same QTL underlie divergence in the same phenotypes across, between, and within watersheds. We find few parallel QTL, even in independent crosses from the same watershed or for phenotypes that have diverged in parallel. These findings suggest that different mutations can lead to similar phenotypes. The low genetic repeatability observed in these lake-stream systems contrasts with the higher genetic repeatability observed in other stickleback systems. We speculate that differences in evolutionary history, gene flow, and/or the strength and direction of selection might explain these differences in genetic parallelism and emphasize that more work is needed to move beyond documenting genetic parallelism to identifying the underlying causes.
最近的研究表明，针对相似生态条件的相似表型的重复进化（这里称为“平行进化”）通常是通过相同基因中的突变发生的。然而，许多以前的研究都集中在有限数量的系统中的已知候选基因上。因此，平行表型进化是由于平行遗传变化引起的频率问题仍然存在。在这里，我们使用来自加拿大温哥华岛四个独立流域的湖泊和溪流之间的三倍棘鱼（Gasterosteus aculeatus）的 F2 杂交群体中的数量性状基因座（QTL）映射来确定相同 QTL 是否是跨流域、流域之间和流域内相同表型分歧的基础。我们发现很少有平行的 QTL，即使在来自同一流域的独立杂交中也是如此，或者对于已经平行分化的表型也是如此。这些发现表明，不同的突变可以导致相似的表型。在这些湖泊 - 溪流系统中观察到的遗传可重复性较低，与在其他棘鱼系统中观察到的较高遗传可重复性形成对比。我们推测，进化历史、基因流和/或选择的强度和方向的差异可能解释了这些遗传平行性的差异，并强调需要做更多的工作来超越记录遗传平行性，以确定潜在的原因。
