Sexual selection and the origin of species: experimental insight into adaptation, the purging of deleterious mutations, and the evolution of sexual isolation

点击翻译按钮获取中文摘要

Darwin had famously wide ranging research interests but preeminent among these were the two branches of my research program: selection in relation to sex and the origin of species. With respect to the former, sexual selection occurs when individuals differ in reproductive success and it can result in the evolution of striking differences between males and females in size, appearance, and behaviour. Indeed, Darwin originally proposed his theory of sexual selection to account for the evolution of such differences, most notably traits like the peacock's tail that are maladaptive in terms of survival. In the intervening years, we have come to understand well sexual selection's role in the evolution of costly sexual traits. However, questions concerning other fundamental aspects of sexual selection remain unanswered and the first branch of my research program addresses two of these. First, does sexual selection promote or hinder adaptation, and second, does it help in removing the harmful mutations that arise every generation in populations? Limited attention has been given to these consequences of sexual selection for nonsexual fitness and the work that has been done tends to involve highly simplified lab environments that may be providing biased insight. My proposal describes a series of experiments that test the various population genetic consequences of sexual selection and whether and how these depend on environmental complexity.***The second branch of my research concerns how new species arise and thus speaks to the origins of a major component of the world's biological diversity. Species are defined by the presence of reproductive barriers that restrict genetic exchange between them. The evolution of sexual isolation, whereby individuals from different populations are less attracted to one another as potential mates, has long been suggested to be a key reproductive barrier that is important in both initiating and completing the speciation process. Although the existence of sexual isolation is straightforward to demonstrate, understanding its evolution requires identifying the underlying traits responsible so that we can determine how they have diverged. Surprisingly, even in the best studied groups of organisms the traits causing sexual isolation are seldom known. My proposal outlines an additional series of experiments that build a comprehensive understanding of the causes of sexual isolation in a pair of N. America mushroom-feeding flies, and in doing so addresses several understudied topics in speciation research. Both branches on my research program rely heavily on a powerful technique called experimental evolution in which we compare how the evolutionary process unfolds in populations under different conditions. The results of this work will have broad implications for our basic understanding of evolution including how adaptation occurs and the diversity of life arises.**