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Associate Professor of Zoology Phone: (405)325-0785 RM/Lab:SH105 |
I study evolutionary and community ecology of freshwater fishes. My current research program has three major foci: 1) evolution of maternal investment tactics, 2) factors affecting structure and dynamics of stream fish communities, and 3) interactions between life-history of constituent species and dynamics of fish assemblages.
Evolution of maternal investment tactics: Ongoing studies in my laboratory (currently funded by the National Science Foundation) address the role of mother-to-embryo transfer of nutrients in maternal provisioning tactics of livebearing fishes of the genus Gambusia. Among poeciliids, this group was long considered to provision offspring only by production of large, yolky eggs (lecithotrophy), but, using injections of radiolabeled nutrients, we have demonstrated that females transfer nutrients to developing embryos (matrotrophy). This finding has important implications for maternal investment strategies in largespring gambusia, and for the evolution of maternal-embryo transfer of nutrients as a reproductive strategy in fishes of the Family Poeciliidae as a whole. Specific studies in my laboratory address variation in matrotrophic provisioning among and within species of Gambusia, patterns of within-brood provisioning in species from different environments, and effects of resource availability and parasitism on matrotrophy. These studies are conducted in my greenhouse laboratory at the University of Oklahoma Aquatic Research Facility.
Factors affecting assemblage structure and dynamics of freshwater fish communities: Another focus of my research program is spatial and temporal variation in structure of fish assemblages and factors that influence assemblage structure. Using data from long-term collections (made by me and William Matthews) in streams of the lower Great Plains, we have addressed a number of questions in community ecology of fishes including: 1) long-term change versus background variation in fish community structure, 2) effects of factors acting at different spatial scales on assemblage structure 3) effects of relative abundance of a common species on structure of the residual assemblage, 4) temporal variation in species associations at different spatial scales, 5) long-term effects of drought on fish assemblage structure, and 6) persistence of species associations and implications for local co-evolution. These analyses of assemblage variation and long-term change typically use multivariate techniques.
In addition to analyses based on field collections, we have taken an experimental approach to examine temporal variation in fish assemblages. Using mesocosm tanks at the University of Oklahoma Biological Station, we have asked if replicate assemblages of fishes change in parallel over time under conditions that exclude major environmental impacts (e.g.,flood, drought) and preclude immigration and emigration.
Interactions between life-history of constituent species and dynamics of fish assemblages: Assemblage variation results from changes in relative abundance of the species composing the assemblage, and those changes, in turn, may be driven by the composition of the assemblage at a given time. There is, therefore, a dynamic and reciprocal interface between life history of species in an assemblage and the structure of the assemblage itself. Experimental manipulations of life history imposed by environmental variation or density manipulations can provide insight into mechanisms acting at this interface. Using mesocosm units at the University of Oklahoma Biological Station, I have conducted studies to address these mechanisms including effects of drought on life history and assemblage structure of a stream fish community (with William Matthews) and effects of density on growth in red shiner (with Keith Gido, Kansas State University and William Matthews).
Kerri E. Pratt M.S. 2000. Life history traits of the rocky shiner, Notropis suttkusi
Paula Raelynn Deaton. Mating behavior, parasites, and life history of Gambusia
Melody Brooks. Effects of resource availability and parasitic infection on host reproductive effort
Ayesha Shakir, B. S. with Honors, 2000. Comparison of sizes of feeding structures of Etheostoma spectabile and Etheostoma lepidum
Cynthia Cheung, B.S. with Honors, 2001. Mother-to-embyro transfer of nutrients in the least killifish and largespring gambusia.
Courtney Wallace. B. S. with Honors. 2003. Effects of size at birth on size at maturity in the western mosquitofish
