The evolutionary causes and consequences of sex and sexual dimorphism

有性繁殖很普遍，在大多数动物和一些植物中，涉及两种性别。拟议研究计划的长期目标是了解有性繁殖的进化原因和后果，特别是在有两种性别的系统中。一个中心目标是对性别选择进行量化，并了解这种选择产生的各种机制。第二个目标是了解两种不同性别进化的后果。其中一组项目的重点是一种既能有性繁殖又能无性繁殖的植物--地钱草。我们将研究来自北美不同地区的这种物种的种群基因组学，以推断种群是否在有性繁殖频率上存在差异。如果是这样的话，我们就会像预测的那样，推断较高的性别率是否对选择的效果产生了积极影响。第二组项目旨在了解性别选择，这是进化生物学的一个重大未知数。公认的理论表明，性别选择应该通过性别如何影响适合度的平均值或方差来发挥作用，但在自然界中，几乎没有数据评估这些影响。在一项实地研究中，我们将测量实验中产生的有性和无性衍生后代的适合度分布。其他试验将集中在测试关键生态源的选择上。第二组项目关注的是男性和女性之间的差异。选择通常在两性中偏爱不同的表型，然而这些表型是由一组基本相同的基因构成的。近年来，对许多动物的研究表明，基因表达的性别二型性很常见，这增加了基因组中的许多基因在两性中被选择为不同表达模式的可能性。然而，导致性别偏见基因表达(SBGE)的选择却知之甚少。利用实验果蝇种群，我们将检查性别偏见基因表达(SBGE)在两个不同进化背景下的变化。首先，我们将研究SBGE是如何随着配偶竞争的变化而进化的，这被认为是有利于二型性的主要力量。在第二个实验中，我们研究了SBGE如何在保持很大一部分基因组主要在一种性别中进化的操作下进化，从而极大地减少了来自另一种性别的任何相互冲突的选择。这项工作的一个主要目标是更好地了解已经二态表达的基因是否正在进行更强的二态选择，以及是否有许多目前没有二态但正在选择成为二态的基因。总体而言，这些项目将提供关于SBGE进化的更清晰的图景，以及使用不同性别共享的基因组进化的后果。

Sexual reproduction is widespread and, in most animals and some plants, involves two sexes. The long-term objective of the proposed research program is to understand the evolutionary causes and consequences of sexual reproduction, especially in systems with two sexes. One central aim is to quantify selection on sex and understand the various mechanisms by which this selection arises. The second aim is to understand the consequences of evolving with two separate sexes. One set of projects focuses on a plant that reproduces both sexually and asexually, the liverwort Marchantia polymorpha. We will study the population genomics of this species from different regions of North America to infer if populations vary in how frequently they reproduce sexually. If so, we will then infer whether higher rates of sex have positively influenced the efficacy of selection, as predicted. A second set of projects aims to understand selection on sex, one of the great unknowns of evolutionary biology. Well-established theory shows that selection on sex should work through how sex affects either the mean or the variance in fitness, yet there is almost no data evaluating these effects in nature. In a field study, we will measure the distribution of fitness of experimentally generated sexually- and asexually-derived offspring. Additional experiments will focus on testing key ecological sources of selection. A second set of projects focuses on differences between males and females. Selection often favours different phenotypes in the two sexes, yet these phenotypes are constructed from a largely shared set of genes. In recent years, studies in many animals have shown sexual dimorphism in gene expression is common, raising the possibility that many genes in the genome are selected for different expression patterns in the two sexes. However, the selection responsible for creating sex-biased gene expression (SBGE) is poorly understood. Using experimental fruit fly populations, we will examine changes in sex-biased gene expression (SBGE) in two different evolutionary contexts. In the first, we will examine how SBGE evolves in response to changes in mate competition, which is thought to be a major force favouring dimorphism. In the second, we examine how SBGE evolves in response to a manipulation that keeps a large portion of the genome evolving mostly in one sex, thereby greatly diminishing any conflicting selection from the other sex. One major goal of this work is to better understand whether genes that are already dimorphically expressed are under on-going selection for even stronger dimorphism and whether there are many genes that are not currently dimorphic but are under selection to become so. Collectively, the projects will provide a clearer picture of the evolution of SBGE and the consequences of evolving with a genome shared by two different sexes.