The Evolutionary Genetics of Sexual Size Dimorphism in a Seed-Feeding Beetle

这项研究将测试关于性状之间的遗传关系如何随着自然选择的反应而变化的理论预测。更具体地说，它将研究在男性和女性中表达不同的特征之间的遗传关系如何随着对男性和女性的不同选择而改变。利用一种很少表现出性别二型性的昆虫物种，实验将一次对一种性别或同时对两种性别的体型进行人工选择(模拟自然界中经常观察到的自然选择模式)，并检查(A)交替(未选择的)性别中相关的进化反应，(B)其他未选择的特征(如生殖特征)的相关反应，以及(C)遗传方差和协方差的进化。这些实验还将对雌性生殖力以及雄性和雌性发育时间进行选择。这将检验这样的假设，即增加繁殖力的选择和短发育时间的选择以理论预测的方式影响性别大小二型性的进化。尽管许多研究研究了性状之间如何在遗传上相互关联，但以前的研究很少研究当性状受到自然选择的影响时，这些遗传关系是如何变化的。然而，自然选择在自然界中无处不在；在农业动植物育种项目中，在农业领域使用杀虫剂期间，在使用抗生素时，以及在自然生物事件被操纵时，人类对生物施加自然选择。当我们对这些性状实施自然选择时，了解这些性状之间的遗传关系是如何变化的，这对于理解种群对这种选择的长期进化反应至关重要。

This study will test theoretical predictions about how genetic relationships between traits change in response to natural selection. More specifically, it will examine how genetic relationships between traits expressed differently in males and females change in response to differing selection on males and females. Using an insect species that exhibits little sexual dimorphism, the experiments will impose artificial selection on the body size of either one sex at a time or both sexes at once (simulating patterns of natural selection often observed in nature) and examine (a) correlated evolutionary responses in the alternate (unselected) sex, (b) correlated responses of other non-selected traits (e.g., reproductive traits), and (c) the evolution of genetic variances and covariances. The experiments will also impose selection on female fecundity, and male and female development time. This will test the hypotheses that selection for increased fecundity and selection for short development time influence the evolution of sexual size dimorphism in a manner predicted by theory.Although many studies have examined how traits are genetically related to each other, few previous studies have examined how these genetic relationships change when traits are subject to natural selection. Yet natural selection is ubiquitous in nature; and human beings impose natural selection on organisms in agricultural animal and plant breeding programs, during application of pesticides to agricultural fields, in the use of antibiotics, and whenever natural biological events are manipulated. Understanding how genetic relationships among traits change as we impose natural selection on these traits is critical to understanding the long-term evolutionary responses of populations to this selection.