Hybridization, sex determination, and evolutionary diversification in freshwater fishes

淡水鱼类的杂交、性别决定和进化多样化

• 批准号: RGPIN-2020-05021
• 负责人: Mandeville, Elizabeth
• 金额: $ 2.4万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=757634
• 关键词: Hybridization; sex; determination; evolutionary; diversification

Hybridization, when closely related species produce offspring, has been an integral part of evolutionary diversification, and is deeply entwined in the evolutionary history of many lineages of plants and animals. While hybridization can promote evolutionary diversification through providing raw material for the rapid formation of new species and promoting novel traits, hybridization can also inhibit diversification by homogenizing newly differentiated lineages. My research focuses on describing how evolutionary processes, specifically hybridization, influence the evolution and maintenance of biodiversity. One relatively unexplored area is describing exactly how major genomic rearrangements, including evolutionary turnover in sex determination mechanisms, influences hybridization outcomes. Sex determining regions of the genome are believed to have been crucially important in the evolution of new species and maintenance of reproductive isolation between nascent species, but our understanding of genetic mechanisms of sex determination is still incomplete in many taxa, including fish. Fish have extremely variable sex determination mechanisms that include genetic sex determination with differentiated sex chromosomes, genetic sex determination without differentiated sex chromosomes (including polygenic systems), individuals that are hermaphrodites, and environmental sex determination. Sex determination systems in fish are known to differ within closely related groups of fish, and even across populations within a species. I hypothesize that sex determination mechanisms have shaped outcomes of hybridization in two groups of freshwater fishes in North America, specifically Catostomus suckers and Chrosomus dace. Both of these evolutionary lineages have been influenced by hybridization, but in very different ways. Catostomus suckers are part of a species-rich, phenotypically diverse, and geographically widespread family (Catostomidae) that arose from an allotetraploid hybrid ancestor approximately 50 million years ago, and extant Catostomus species hybridize extensively. In contrast, Chrosomus dace present a much different outcome of a hybridization event believed to have occurred between C. eos and C. neogaeus approximately 50,000 years ago, namely the origin of gynogenesis, a rare phenomenon where unisexual, asexual hybrid lineages reproduce clonally. I will use genomic data to describe the genetic basis of sex determination for both Catostomus and Chrosomus species, and identify how genetic sex determination mechanisms have shaped outcomes of both historical and contemporary hybridization in these lineages. By explicitly linking sex determination with hybridization outcomes for these two lineages, I will advance our understanding of how sex-determining loci might be more broadly implicated in evolutionary diversification and the maintenance of biodiversity.

当亲缘关系密切的物种产生后代时，杂交一直是进化多样化的一个组成部分，并且在许多植物和动物的进化历史中深深纠缠在一起。杂交可以通过为新物种的快速形成提供原料和促进新性状来促进进化多样化，但杂交也可以通过使新分化的谱系同质化来抑制进化多样化。我的研究重点是描述进化过程，特别是杂交，如何影响生物多样性的进化和维持。一个相对未开发的领域是准确描述主要的基因组重排，包括性别决定机制的进化转换，是如何影响杂交结果的。基因组的性别决定区域被认为对新物种的进化和维持新生物种之间的生殖隔离至关重要，但我们对许多分类群（包括鱼类）性别决定的遗传机制的理解仍然不完整。鱼类的性别决定机制千差万别，包括有分化性染色体的遗传性别决定、没有分化性染色体的遗传性别决定（包括多基因系统）、雌雄同体个体和环境性别决定。已知鱼类的性别决定系统在密切相关的鱼类群体中是不同的，甚至在同一物种的不同种群中也是不同的。我假设性别决定机制影响了北美两类淡水鱼的杂交结果，特别是吸嘴鱼（Catostomus suckers）和鲤鱼（Chrosomus dace）。这两种进化谱系都受到杂交的影响，但方式非常不同。Catostomus吸盘是一个物种丰富，表型多样，地理分布广泛的家族（Catostomidae）的一部分，该家族起源于大约5000万年前的异源四倍体杂交祖先，现存的Catostomus物种广泛杂交。相比之下，在大约5万年前发生在C. eos和C. neogaeus之间的杂交事件中，染色体呈现出截然不同的结果，即雌性生殖的起源，这是一种罕见的现象，即单性、无性杂交谱系无性繁殖。我将使用基因组数据来描述Catostomus和Chrosomus物种性别决定的遗传基础，并确定遗传性别决定机制如何影响这些谱系中历史和当代杂交的结果。通过明确地将性别决定与这两个谱系的杂交结果联系起来，我将推进我们对性别决定位点如何更广泛地参与进化多样化和生物多样性维持的理解。