9532071 CHARLESWORTH This research will test recent theories that highly selfing species should be depauperate in neutral variation. Theoretically, the pattern and amount of genetic variation in plant populations are greatly influenced by the mating system which, in turn, is strongly influenced by the self-fertilization rate. Nucleotide sequence variation will be quantified in a group of plants with known differences in self-fertilization rates (Leavenworthia ; Brassicaceae). The resulting data will allow the comparison of levels of neutral and fitness-related variation at the nucleotide level among taxa with diverse breeding systems. Understanding the influence of inbreeding on genetic variability at neutral and fitness related loci, and the causes of differences in each kind of genetic diversity among populations, is important in relation to all aspects of plant genetics. Findings on genetic variation from natural populations will also be of value for plant genetic conservation. Conservation biologists assume that inbreeding taxa are highly susceptible to environmental degradation, because of their low reservoir of genetic variability in traits affecting fitness. The funded research addresses the validity of this assumption by quantifying fitness-related genetic variation for such highly inbred populations. The nucleotide sequence data can be further utilized for inferring the phylogeny of the group studied. This will, in turn, ppovide a valuable framework for understanding the evolutionary history of breeding system traits and life history characters in the genus.
