Evolution of Mating Systems in the Limnadiid Clam Shrimp

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Among the diversity of reproductive types in plants and animals, one permutation - androdioecy (mixtures of males and hermaphrodites) - is distinguished by its rarity, being found in only 18 cases. Two of these 18 species are found in the primitive crustacean class Branchiopoda, but another 20 branchiopod species (in the genus Eulimnadia) have sex ratios suggestive of androdioecy. If these 20+ closely-related species are truly androdioecious, then this rare mating system would likely have been present in the ancestor to this lineage, placing the origin of androdioecy at ~280 million years ago. This inferred age is orders of magnitude older than expected by theory. We propose to combine three parallel projects (laboratory rearing experiments, morphological comparisons, and DNA sequencing) to assess whether androdioecy is an ancestral or derived trait in these crustaceans. The rearing experiments will be used to determine the extent of androdioecy in these species. The morphological and DNA projects will produce data used to estimate the relationships among species within these crustaceans. We will measure 30 morphological characters per species as well as sequence four DNA regions, which should enable a robust estimate of evolutionary relationships among these animals. We will then use these estimates to determine whether androdioecy is an ancestral condition for these crustaceans, which if true, suggests that this reproductive mode may have persisted for hundreds of millions of years, casting doubt on the notion that androdioecy is a transitory reproductive system. This research project will accomplish two scientific and three educational goals. First, these data will allow us to better understand the factors that maintain males with hermaphrodites in androdioecious species, which can shed light on the importance of mating between individuals relative to self-fertilization. Such an understanding can help us to formulate better management practices for both domesticated plants and animals as well better preservation plans for endangered species. Second, delineating the true relationship among the species within this crustacean group will be helpful for determining the true number of species in North America, which can be used to shed light on which of these species may be threatened or endangered in the United States. For the educational components of this research, this project will integrate teaching and primary research on three levels. First, funding will directly support two graduate students and one undergraduate student for three years. Second, all three PI's will encourage undergraduate students to participate in research via independent research projects and honors thesis research. Third, part of this research program will be incorporated into two on-going educational programs at The University of Akron: (a) an NSF-funded program that brings basic research into the laboratories of the Introductory Biology course at U of A, and (b) a 5-year, privately funded program that involves minority high school students in basic research at U of A via a mentoring program, involving both undergraduate and graduate students in a "research team." In all research mentoring programs, priority will be given to qualified minority and women candidates at all levels of participation.