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

这项研究将检验关于性状之间的遗传关系如何随着自然选择而变化的理论预测。更具体地说，它将研究在男性和女性的不同选择下，男性和女性表达不同特征之间的遗传关系是如何变化的。实验将使用一种几乎没有两性二态性的昆虫物种，对一种性别的体型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)替代（未选择）性别的相关进化反应，(b)其他非选择特征（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的繁殖力以及雄性和雌性的发育时间施加选择。这将验证这样的假设，即选择增加繁殖力和选择较短的发育时间以理论预测的方式影响性别大小二态性的进化。尽管许多研究已经研究了性状之间的遗传关系，但很少有先前的研究考察了性状在自然选择下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；在农业动物和植物育种计划中，在农田使用杀虫剂时，在抗生素的使用中，以及在任何自然生物事件被操纵的时候，人类都将自然选择强加给生物体。理解性状之间的遗传关系是如何在我们对这些性状施加自然选择时发生变化的，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.