DISSERTATION RESEARCH: Mechanisms of reproductive isolation along the speciation continuum: from micro- to macro-evolutionary scales

这个项目将研究维持种群、物种和更遥远的血统的多样性的力量，以建立一个更全面的加州珠光花物种形成过程的图景。了解新物种是如何从现有物种起源的是生物学的一个主要目标。在新物种形成后，生态和遗传力量都可能起到保护物种边界、防止杂交和维持生物多样性的作用。目前还不清楚这些力量是否在种群、物种和更高的分类水平上起到了类似的作用。全面了解生物多样性是如何在一组植物中产生和维持的，将为维持地球生物多样性的基本模型提供信息。它还将指导针对较小、孤立或分散的种群的重要保护和管理决策。这项研究将提供一名研究生和几名本科生研究助理的培训。它还将通过对加州植物生物多样性的公共宣传努力，为公民提供更丰富的背景，了解植物生物多样性。以前对链霉菌属植物物种形成中后期的研究表明，遗传不亲和性和不同的生态都有助于维持物种水平的多样性。实验杂交表明，遗传不亲和性随着物种分化次数的增加而增加。然而，一些最近出现分歧的物种对仍然可以在温室里产生可行的杂交后代。野外研究表明，这些物种之间的生态差异，包括小生境亲和力、传粉者的喜好和稳定性以及物候学，可能在保持潜在的杂交物种在自然界中的独特地位方面发挥作用。目前尚不清楚是否相同的生态和进化力量在物种形成连续体的不同阶段发挥作用，或者不同的遗传和生态力量是否具有物种形成的每个阶段的特征。这项研究通过在种群水平上关注种群分化和早期生殖隔离，更深入地探讨了链霉菌物种形成的早期阶段。实验杂交和限制性内切酶位点相关DNA测序将用于检测多个地理和环境差异的布氏葡萄球菌种群之间的遗传关联模式。同样的技术也将被用于在种群水平上分析遗传、地理和环境距离对生殖隔离的影响。这项研究补充了链霉菌以前的工作，提供了关于种群水平过程的新数据，这些数据将阐明在物种水平上观察到的生殖隔离模式，并提供一个单一研究系统内物种形成过程的综合视图。

This project will examine the forces maintaining diversity in populations, species, and more distantly related lineages to build a more comprehensive picture of the speciation process in California Jewelflowers. Understanding how new species originate from existing ones is a major goal in biology. After new species are formed, both ecological and genetic forces may act to preserve species boundaries, prevent hybridization, and maintain biodiversity. It is unclear if these forces act similarly at population, species, and higher taxonomic levels. A comprehensive understanding of how biodiversity is generated and maintained in a single group of plants will inform basic models of the maintenance of Earth's biodiversity. It will also guide important conservation and management decisions for small, isolated, or fragmented populations. This research will provide training of a graduate student and several undergraduate research assistants. It will also provide citizens with a richer context for understanding plant biodiversity through public outreach efforts on California's plant biodiversity. Previous research at the middle and late stages of speciation in the plant clade Streptanthus suggests that both genetic incompatibilities and divergent ecology contribute to the maintenance of species-level diversity. Experimental hybridizations show that genetic incompatibility increases with species divergence times. Some recently diverged species pairs can, however, still produce viable hybrid offspring in the greenhouse. Field research shows that ecological differences in such species, including microhabitat affinity, pollinator preferences and constancy, and phenology may play a role in maintaining potential interbreeders as distinct species in nature. It is unclear whether the same ecological and evolutionary forces act at different stages of the speciation continuum, or if distinct genetic and ecological forces are characteristic of each stage of speciation. This research delves deeper into the early stages of speciation in Streptanthus, by focusing on population divergence and early reproductive isolation at the population level. Experimental hybridizations and Restriction site Associated DNA sequencing will be used to examine patterns of genetic relatedness among multiple geographically and environmentally divergent populations of S. breweri. The same techniques will also be used to analyze the influence of genetic, geographic, and environmental distance, on reproductive isolation at the population level. This research complements previous work in Streptanthus, providing new data on population-level processes, which will illuminate patterns of reproductive isolation observed at the species level, and provide a comprehensive view of the speciation process within a single study system.