Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706, USA.
G3 (Bethesda). 2022 Mar 4;12(3). doi: 10.1093/g3journal/jkab454.
Important uncertainties persist regarding the genetic architecture of adaptive trait evolution in natural populations, including the number of genetic variants involved, whether they are drawn from standing genetic variation, and whether directional selection drives them to complete fixation. Here, we take advantage of a unique natural population of Drosophila melanogaster from the Ethiopian highlands, which has evolved larger body size than any other known population of this species. We apply a bulk segregant quantitative trait locus mapping approach to 4 unique crosses between highland Ethiopian and lowland Zambian populations for both thorax length and wing length. Results indicated a persistently variable genetic basis for these evolved traits (with largely distinct sets of quantitative trait loci for each cross), and at least a moderately polygenic architecture with relatively strong effects present. We complemented these mapping experiments with population genetic analyses of quantitative trait locus regions and gene ontology enrichment analysis, generating strong hypotheses for specific genes and functional processes that may have contributed to these adaptive trait changes. Finally, we find that the genetic architectures indicated by our quantitative trait locus mapping results for size traits mirror those from similar experiments on other recently evolved traits in this species. Collectively, these studies suggest a recurring pattern of polygenic adaptation in this species, in which causative variants do not approach fixation and moderately strong effect loci are present.
关于自然种群中适应性特征进化的遗传结构仍然存在重要的不确定性，包括涉及的遗传变异数量、它们是否来自现有遗传变异，以及是否定向选择使它们完全固定。在这里，我们利用了一个来自埃塞俄比亚高地的独特的黑腹果蝇自然种群，该种群的体型比该物种的任何其他已知种群都要大。我们应用了一种批量分离数量性状基因座作图方法，对来自埃塞俄比亚高地和赞比亚低地的 4 个独特种群进行了胸部长度和翅膀长度的杂交。结果表明，这些进化特征的遗传基础存在持续的可变性（每个杂交种都有很大不同的数量性状基因座），并且具有至少中度多基因遗传结构，存在相对较强的效应。我们通过对数量性状基因座区域的群体遗传分析和基因本体富集分析补充了这些作图实验，为可能促成这些适应性特征变化的特定基因和功能过程生成了强有力的假说。最后，我们发现，我们对大小特征的数量性状基因座作图结果所表明的遗传结构与该物种中其他最近进化特征的类似实验结果相吻合。总的来说，这些研究表明，该物种中存在一种反复出现的多基因适应模式，其中因果变异不会接近固定，并且存在适度强效应的基因座。
