Fowler-Finn K D, Cruz D C, Rodríguez R L
Department of Biology, Saint Louis University, Saint Louis, MO, USA.
Behavioral and Molecular Ecology Group, Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI, USA.
J Evol Biol. 2017 Jan;30(1):13-25. doi: 10.1111/jeb.12994. Epub 2016 Nov 14.
Many animals exhibit social plasticity - changes in phenotype or behaviour in response to experience with conspecifics that change how evolutionary processes like sexual selection play out. Here, we asked whether social plasticity arising from variation in local population density in male advertisement signals and female mate preferences influences the form of sexual selection. We manipulated local density and determined whether this changed how the distribution of male signals overlapped with female preferences - the signal preference relationship. We specifically look at the shape of female mate preference functions, which, when compared to signal distributions, provide hypotheses about the form of sexual selection. We used Enchenopa binotata treehoppers, a group of plant-feeding insects that exhibit natural variation in local densities across individual host plants, populations, species and years. We measured male signal frequency and female preference functions across the density treatments. We found that male signals varied across local social groups, but not according to local density. By contrast, female preferences varied with local density - favouring higher signal frequencies in denser environments. Thus, local density changes the signal-preference relationship and, consequently, the expected form of sexual selection. We found no influence of sex ratio on the signal-preference relationship. Our findings suggest that plasticity arising from variation in local group density and composition can alter the form of sexual selection with potentially important consequences both for the maintenance of variation and for speciation.
许多动物表现出社会可塑性——即表型或行为会因与同种个体的经历而发生变化，这会改变诸如性选择等进化过程的展开方式。在此，我们探讨了因雄性求偶信号和雌性配偶偏好的局部种群密度变化而产生的社会可塑性是否会影响性选择的形式。我们操控了局部密度，并确定这是否改变了雄性信号分布与雌性偏好的重叠方式——即信号偏好关系。我们特别关注雌性配偶偏好函数的形状，将其与信号分布相比较时，能为性选择的形式提供假设。我们使用了双色恩氏角蝉，这是一类以植物为食的昆虫，它们在个体寄主植物、种群、物种以及年份间的局部密度存在自然变异。我们测量了密度处理条件下雄性信号频率和雌性偏好函数。我们发现，雄性信号在不同局部社会群体间存在差异，但并非取决于局部密度。相比之下，雌性偏好随局部密度而变化——在密度更高的环境中更偏好较高的信号频率。因此，局部密度改变了信号偏好关系，进而改变了性选择的预期形式。我们发现性别比例对信号偏好关系没有影响。我们的研究结果表明，局部群体密度和组成的变化所产生的可塑性能够改变性选择的形式，这对变异的维持和物种形成可能具有潜在的重要影响。
