DISSERTATION RESEARCH: Effects of environmental stress on multiple generations of interpopulation hybridization.

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It is well established that interpopulation hybrids can experience enhanced fitness in the first generation, followed by depressed fitness in the second generation. Some evidence suggests hybrid fitness problems can be repaired in later generations, and that hybrids may be favored under environmental stress. This study uses the intertidal copepod Tigriopus californicus to assess hybridization over multiple generations in both benign and stressful conditions (high salinity). Experimental hybrid populations will be maintained for up to 17 months and assayed for genetic, morphometric and fitness components every two generations. Tigriopus' short generation time, ease of husbandry and abundance of population-specific molecular markers make it a particularly tractable system for this type of experiment.Results will test the specific hypothesis that hybridization can create genetic variants that are favored under environmental stress, and will help to elucidate the role of hybridization in the formation of new species. This work is also directly relevant to current concerns about the impacts of invasive species mixing with native populations, or farmed organisms mixing with wild populations. Using the Tigriopus model system allows the effects of benign vs. stressful conditions to be assessed in a rigorous fashion that would be difficult to achieve for most species of concern. Additionally, this project supports opportunities for undergraduate research and training at a university that serves a broad and diverse urban area.