Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Sweden.
Department of Evolutionary Biology, Institute for Biological Research "Siniša Stanković, " University of Belgrade, Bulevar despota Stefana 142, Belgrade 11060, Serbia.
Evolution. 2018 Mar;72(3):518-530. doi: 10.1111/evo.13412. Epub 2018 Jan 29.
Whether sexual selection generally promotes or impedes population persistence remains an open question. Intralocus sexual conflict (IaSC) can render sexual selection in males detrimental to the population by increasing the frequency of alleles with positive effects on male reproductive success but negative effects on female fecundity. Recent modeling based on fitness landscape theory, however, indicates that the relative impact of IaSC may be reduced in maladapted populations and that sexual selection therefore might promote adaptation when it is most needed. Here, we test this prediction using bean beetles that had undergone 80 generations of experimental evolution on two alternative host plants. We isolated and assessed the effect of maladaptation on sex-specific strengths of selection and IaSC by cross-rearing the two experimental evolution regimes on the alternative hosts and estimating within-population genetic (co)variance for fitness in males and females. Two key predictions were upheld: males generally experienced stronger selection compared to females and maladaptation increased selection in females. However, maladaptation consistently decreased male-bias in the strength of selection and IaSC was not reduced in maladapted populations. These findings imply that sexual selection can be disrupted in stressful environmental conditions, thus reducing one of the potential benefits of sexual reproduction in maladapted populations.
性选择是否普遍促进或阻碍种群的持续存在仍然是一个悬而未决的问题。 基因内性冲突（IaSC）可以通过增加对雄性生殖成功有积极影响但对雌性生育力有负面影响的等位基因的频率，从而使雄性的性选择对种群产生不利影响。 然而，基于适应度景观理论的最近建模表明，IaSC 的相对影响在适应不良的种群中可能会降低，因此，当最需要时，性选择可能会促进适应。 在这里，我们使用在两种替代寄主植物上经历了 80 代实验进化的豆象甲虫来检验这一预测。 我们通过在替代寄主上交叉饲养两种实验进化种群并估计雄性和雌性适合度的种群内遗传（协）方差，来分离和评估适应不良对性别特异性选择强度和 IaSC 的影响。 两个关键预测得到了支持：与雌性相比，雄性通常经历更强的选择，而适应不良会增加雌性的选择。 然而，适应不良始终降低了选择中的雄性偏度，并且在适应不良的种群中没有降低 IaSC。 这些发现意味着在压力环境条件下，性选择可能会受到干扰，从而降低了适应不良种群中性繁殖的潜在益处之一。
