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

点击翻译按钮获取中文摘要

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.