Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.
J Evol Biol. 2012 Dec;25(12):2537-46. doi: 10.1111/j.1420-9101.2012.02618.x. Epub 2012 Oct 1.
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, that is, 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 competitions 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. Although 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.
由于突变，有害等位基因不断被引入到种群中。在分裂的种群中，这些突变的影响取决于选择的强度以及选择的柔软度，即适应度受局部而非全局竞争支配的程度。人们普遍认识到，竞争的强度和类型会影响对有害突变的选择，但大多数实证研究仅关注竞争对选择强度的影响。然而，尽管竞争是软选择的概念根源，但在选择柔软度的背景下，竞争很少被研究。在其他条件相同的情况下，理论预测种间和种内竞争对选择柔软度有相反的影响。我们使用黑腹果蝇估计了在“基线”竞争环境以及另外两个具有更多种内或种间竞争的竞争环境中选择的强度和柔软度。我们发现竞争环境对选择的平均强度几乎没有影响。虽然选择的柔软度受到竞争类型的影响，但不同基因的测试中变化的方向不同，这与预期相反。尽管“硬/软”选择范式隐含地假设所有个体对局部竞争环境都同样敏感，但我们发现事实并非如此。野生型个体比突变型个体对其本地竞争者遗传质量的变化更敏感。
