Data from: The effects of competition on the strength and softness of selection

Deleterious alleles are constantly introduced into populations due to mutation. In subdivided populations, the impact of these mutations depends on the strength of selection as well as the softness of selection, i.e., the extent to which fitness is governed by local rather than global competition. It is widely appreciated that the intensity and type of competition will affect selection on deleterious mutations but most empirical work has focused solely on the effects of competition on selection strength. However, competition has rarely been studied in the context of selection ‘softness’ even though competition is at the conceptual root of soft selection. All other things being equal, theory predicts that inter- and intraspecific competition have opposing effects on the softness of selection. Using Drosophila melanogaster, we estimated the strength and softness of selection in a “baseline” competitive environment as well as two additional competitive environments characterized by either additional intra- or interspecific competitors. We found that competitive environment had little effect on the average strength of selection. While the softness of selection was affected by the type of competition, the direction of change varied across tests of different genes, contrary to expectation. Though the “hard/soft” selection paradigm implicitly assumes that all individuals are equally sensitive to the local competitive environment, we found this not to be the case. Wild-type individuals were more sensitive to changes in the genetic quality of their local competitors than mutant individuals.突变会持续向种群中引入有害等位基因（deleterious alleles）。在结构分化的种群中，这类突变的影响取决于选择强度以及选择柔度（softness of selection），即适合度由局部而非全局竞争决定的程度。学界普遍认为，竞争的强度与类型会作用于有害突变的选择，但多数实证研究仅关注了竞争对选择强度的影响。然而，尽管竞争是软选择（soft selection）概念的核心根源，却极少有研究在选择柔度的框架下探讨竞争的作用。在其他条件一致的情况下，理论预测种间竞争与种内竞争对选择柔度的影响方向相反。本研究以黑腹果蝇（Drosophila melanogaster）为实验材料，在“基准”竞争环境以及另外两种分别以额外种内竞争者或额外种间竞争者为特征的竞争环境中，评估了选择强度与选择柔度。研究结果显示，竞争环境对选择强度的平均水平几乎无影响。尽管选择柔度确实会受竞争类型的影响，但与理论预期相悖的是，其变化方向因不同基因的检测实验而异。尽管“硬/软选择”范式（hard/soft selection paradigm）默认所有个体对局部竞争环境的敏感程度均一，但本研究发现实际情况并非如此。野生型个体相较于突变型个体，对本地竞争者的遗传质量变化更为敏感。