REU: Genetic Structure within Oak Populations

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The genetic structure of populations can range from one large interbreeding population with genetic variation distributed throughout to a series of small interbreeding subpopulations which are genetically differentiated from each other. The genetic structure of populations results from the interactions of gene flow, natural selection, and genetic drift and also influences how these evolutionary forces will affect that population. The proposed research will determine whether natural selection can cause genetic differentiation within forest tree populations by measuring mating system (i.e. the degree of outcrossing), local selection due to microhabitat, and population genetic structure of two oak species, white oak (Quercus alba) and red oak (Q. rubra). This study will be conducted over a three year period in an oak-hickory forest in central eastern Missouri. Most of the research will be conducted within a 4 ha study plot which contains four types of microhabitat: north- facing slope, southwest-facing slope, west-facing slope, and bottom land. Genetic structure will be described with F- statistics and other appropriate measures using enzyme genetic markers identified through starch gel electrophoresis. The mating system for each species will be measured each year also using enzyme genetic markers. Local selection due to microhabitat will be studied using a reciprocal transplant experiment. The project addresses significant questions for evolutionary biologists about the potential of local selection to influence population structure in angiosperm tree species which may have high outcrossing rates. This study will also provide useful genetic information on an ecologically and economically significant genus in North American forests. Oaks are a valuable commodity for lumber and they provide crucial resources for wildlife. Understanding the distribution of genetic variation within a forest species will help in determining sampling schemes for forest management. In addition, such information will help us understand the ability of increasingly fragmented forest tree populations to respond to natural and human-induced stress.