Dissertation Research: Local Genetic Differentiation and Adaptation of Quantitative Traits

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The research outlined in this proposal will examine the genetic and evolutionary consequences of inbreeding in a population of the self-fertilizing annual plant, Polygonum douglasii. Inbreeding occurs frequently in natural populations of animals and plants, and has several important genetic consequences which tend to reduce the overall genetic variation in a population via random genetic drift. One extreme form of inbreeding is exhibited by plants which habitually self-fertilize their seeds and do not rely on pollen from other plants. Self- fertilizing plant populations are quite common in both wild and crop species. These populations are thought to contain no genetic variability for ecologically important traits and therefore can not respond to natural selection in different environments. In this sense they are thought to be "evolutionary dead-ends." This belief has not yet been thoroughly tested, but some recent theoretical and experimental results suggest that substantial genetic variation may be present within even highly selfing populations. This study will test hypotheses regarding genetic variability and adaptation to specific environments by relating the pattern of genetic differentiation in ecologically important traits to (1) the level of inbreeding, (2) the local environments, and (3) the spatial scale of local adaptation in a single large population of P. douglasii. Breeding experiments in the greenhouse and transplantations in the field will evaluate the extent to which this population contains sufficient genetic variation to adapt to different environments. The experiments will also address whether the population is in fact adapted to a natural range of environments in the field. This study will help to clarify many controversies regarding the evolutionary potential of inbreeding species, issues which are important in designing strategies for improving the ability of the many selfing crop species to thrive in a wide range of environments.