Temporal Changes in Fitness, Morphology and Genetic Composition of Experimental Hybrid Swarms

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Recent work has used the marine copepod Tigriopus californicus as a model for understanding the cause of genetic incompatibilities in the early generations of hybridization between divergent populations. This proposal seeks to extend this work to patterns of fitness, morphology and genetic composition in freely mating hybrid swarms over tens of generations. Replicate hybrid swarms will be established for two different pairs of populations, with different starting frequencies for the two parental types. Over a period of 2 1/2 years, subsamples will be removed from each swarm at regular intervals and assayed for fitness, morphology and a series of molecular markers.Such work is relevant to agricultural issues involving introgression between wild and crop plants and the probability of genetic assimilation. Results may also have applications to fisheries and wildlife management due to concern over the duration of outbreeding depression and the potential for purging deleterious combinations. Lastly, the work will contribute to fundamental evolutionary questions involving the nature of species boundaries and the role of hybridization in creating new species.