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

该项目将研究维持种群、物种和更远的亲缘谱系多样性的力量，以建立一个更全面的加州珠宝花物种形成过程的图景。了解新物种如何从现有物种起源是生物学的一个主要目标。在新物种形成后，生态和遗传的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。目前尚不清楚这些力量是否在种群、物种和更高的分类水平上起着相似的作用。全面了解生物多样性是如何在单一植物群中产生和维持的，将为维持地球生物多样性的基本模型提供信息。它还将指导小型、孤立或分散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。它还将通过加州植物生物多样性的公共宣传工作，为公民提供了解植物生物多样性的更丰富的背景。此前对链蕨属植物进化枝物种形成中后期的研究表明，遗传不相容和生态分化都有助于维持物种水平的多样性。实验杂交表明，遗传不亲和性随物种分化次数的增加而增加。然而，一些最近分化的物种对仍然可以在温室中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，包括微生境亲和性、传粉者偏好和稳定性以及物候学，可能在维持潜在的杂交育种者作为自然中独特的物种方面发挥作用。同样的生态和进化力量是否在物种形成连续体的不同阶段起作用，或者是否不同的遗传和生态力量是物种形成的每个阶段的特征，目前还不清楚。本研究通过关注种群水平上的种群分化和早期生殖隔离，深入探讨了链蕨属物种形成的早期阶段。实验杂交和限制性内切位点相关DNA测序将用于研究啤酒酵母多个地理和环境差异种群之间的遗传相关性模式。同样的技术也将用于分析遗传、地理和环境距离对种群一级生殖隔离的影响。本研究补充了前人在链甲上的工作，提供了种群水平过程的新数据，阐明了在物种水平上观察到的生殖隔离模式，并提供了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.