Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
G3 (Bethesda). 2021 Aug 7;11(8). doi: 10.1093/g3journal/jkab168.
Life history traits underlie the fitness of organisms and are under strong natural selection. A new mutation that positively impacts a life history trait will likely increase in frequency and become fixed in a population (e.g., a selective sweep). The identification of the beneficial alleles that underlie selective sweeps provides insights into the mechanisms that occurred during the evolution of a species. In the global population of Caenorhabditis elegans, we previously identified selective sweeps that have drastically reduced chromosomal-scale genetic diversity in the species. Here, we measured the fecundity of 121 wild C. elegans strains, including many recently isolated divergent strains from the Hawaiian islands and found that strains with larger swept genomic regions have significantly higher fecundity than strains without evidence of the recent selective sweeps. We used genome-wide association (GWA) mapping to identify three quantitative trait loci (QTL) underlying the fecundity variation. In addition, we mapped previous fecundity data from wild C. elegans strains and C. elegans recombinant inbred advanced intercross lines that were grown in various conditions and detected eight QTL using GWA and linkage mappings. These QTL show the genetic complexity of fecundity across this species. Moreover, the haplotype structure in each GWA QTL region revealed correlations with recent selective sweeps in the C. elegans population. North American and European strains had significantly higher fecundity than most strains from Hawaii, a hypothesized origin of the C. elegans species, suggesting that beneficial alleles that caused increased fecundity could underlie the selective sweeps during the worldwide expansion of C. elegans.
生活史特征是生物体适应性的基础，受到强烈的自然选择的影响。一个对生活史特征有积极影响的新突变很可能会增加频率，并在种群中固定下来（例如，选择清除）。鉴定出构成选择清除的有益等位基因，可以深入了解物种进化过程中发生的机制。在全球的秀丽隐杆线虫种群中，我们之前已经鉴定出了选择清除，这些清除导致了该物种染色体规模遗传多样性的急剧减少。在这里，我们测量了 121 个野生秀丽隐杆线虫菌株的繁殖力，包括许多最近从夏威夷群岛分离出来的分化菌株，发现具有更大清除基因组区域的菌株的繁殖力明显高于没有最近选择清除证据的菌株。我们使用全基因组关联 (GWA) 图谱来鉴定三个与繁殖力变化相关的数量性状基因座 (QTL)。此外，我们还绘制了来自野生秀丽隐杆线虫菌株和在不同条件下生长的秀丽隐杆线虫重组近交系高级互交系的先前繁殖力数据，并使用 GWA 和连锁图谱检测到了八个 QTL。这些 QTL 显示了该物种繁殖力的遗传复杂性。此外，每个 GWA QTL 区域的单倍型结构与秀丽隐杆线虫种群中的近期选择清除存在相关性。北美和欧洲的菌株比来自夏威夷的大多数菌株的繁殖力都要高，夏威夷被认为是秀丽隐杆线虫物种的起源地，这表明导致繁殖力增加的有益等位基因可能是秀丽隐杆线虫在全球扩张过程中的选择清除的基础。
