Sex-specific selection and the evolution of sexual dimorphism

两性二态性可以说是动物王国中最普遍的种内多样性形式，影响许多表型，包括形态、生理、行为和生活史。我提出了六个不同的目标，围绕三个相关主题组织：1 .两性二态性和性别偏见基因表达。对于许多二态现象来说，存在于两性中的基因在两性之间的基因表达差异（性别偏倚表达）是关键。许多研究试图将性别偏向基因与性选择联系起来，但结果却极不一致。这可能是我们目前从许多细胞类型的复杂聚集中测量基因表达方式的产物，这种方式无法确定性别偏倚表达是相似细胞内调节差异（细胞类型内重新布线）的结果，还是由于性别特异性发育轨迹导致的细胞类型丰度差异。我们最近在实验室安装了最先进的单细胞RNA-Seq （ScRNA-Seq）系统，以区分由于细胞类型的调节性重编程引起的基因表达差异和由于细胞类型丰度的发育差异引起的基因表达差异。我们将利用这项研究来研究性别偏倚基因表达的原因和分子特征，并确定我们是否确实可以在性别偏倚基因的分子特征中研究性选择。2。性别特异性选择如何塑造基因组多样性？我们最近实施了生物信息学和群体基因组学方法，从几代人的全基因组DNA测序数据中检测性别特异性选择和性别冲突的微妙但清晰的信号。这是先前测量性别偏倚基因分子进化特性的一个重大进展，因为它允许我们在生态相关的时间尺度内工作，并比较不同生态的种群。此外，这种方法使确定性冲突的原因成为可能。我们将采用这种方法来研究性别冲突在生命周期和不同自然种群中的足迹。3。为什么性染色体分化的速度截然不同？性染色体是基因组中唯一一个不同性别的区域。性染色体研究的一个关键问题是为什么一些性染色体保持同态，而另一些性染色体在X和y之间表现出深刻的差异。我们最近对几个Poeciliid物种的性染色体进行了表征，揭示了单个性染色体系统的性染色体分化程度在物种内和物种间都是高度变化的。因此，这个分支是性染色体进化的一个强大的自然复制，可以用来理解Y染色体分化和退化的差异。我们将利用这种多样性来探究是什么阻止了一些Y染色体在其他Y染色体迅速分化的情况下衰变。

Sexual dimorphism is arguably the most pervasive form of intra-specific diversity in the animal kingdom, affecting many phenotypes, including morphology, physiology, behaviour and life history. I propose six different objectives, organized around three related themes: I. Sexual dimorphism and sex-biased gene expression. For many dimorphisms, gene expression differences between males and females (sex-biased expression) for genes present in both sexes are key. Many studies have tried to connect sex-biased genes to sexual selection, with profoundly discordant results. This is likely a product of the way we currently measure gene expression from complex aggregations of many cell types, which cannot determine whether sex-biased expression is the result of regulatory differences within similar cells (rewiring within cell types), or is due to differences in the abundance of cell types resulting from sex-specific developmental trajactories. We have recently installed a state-of-the-art single-cell RNA-Seq (ScRNA-Seq) system in the lab to differentiate gene expression differences due to regulatory reprogramming of cell types from those due to developmental differences in cell type abundance. We will use this study the cause and molecular signatures of sex-biased gene expression, and determine whether we can indeed study sexual selection in the molecular signature of sex-biased genes. II. How does sex-specific selection shape genomic diversity? We have recently implemented bioinformatic and population genomic approaches to detect the subtle but clear signal of sex-specific selection and sexual conflict from whole-genome DNA sequencing data within generations. This is a major advance on previous work measuring molecular evolutionary properties of sex-biased genes, as it allows us to work within ecologically relevant time scales and compare populations with different ecologies. Moreover, this approach makes it possible to determine the causes of sexual conflict. We will implement this approach to study the footprint of sexual conflict over the life cycle and across different natural populations. III. Why do sex chromosomes diverge at radically different rates? Sex chromosomes are the only region of the genome that differ between the sexes. A key question in sex chromosome research is why some sex chromosomes remain homomorphic, while others show profound differences between the X and Y. We recently characterized the sex chromosomes across several Poeciliid species, revealing that the degree of sex chromosomes differentiation is highly variable both within and across species for a single sex chromosome system. This clade therefore is a powerful natural replicate of sex chromosome evolution that can be used to understand differences in divergence and degradation of the Y chromosome. We will leverage this diversity to ask what prevents some Y chromosomes from decaying while others diverge so quickly.