This project explores evolutionary mechanisms for the origin, refinement, and maintenance of integrated genetic systems. Genetic systems of this kind include systems of reproduction, comprising interacting components that regulate the various aspects of reproduction from mate choice to selection among offspring. Two major objectives are addressed. First, inbreeding depression due to deleterious mutations at arbitrary numbers of loci and its implications for the evolutionary modification of the reproductive system will be explored. Previous work has shown that because shifts in any component of the genetic system induce correlated changes and genetic associations throughout the system, the process of the evolution of reproduction cannot be determined without reference to the genetic basis of in g depression. The nature and magnitude of associations that arise in partially inbred populations among loci subject to deleterious mutation will be explored. Once this genetic structure is determined, the evolutionary modification of self-fertilization, self-incompatibility, and linkage will be studied. The second major component concerns the origin and maintenance of incompatibility in flowering plants. Studies to be conducted will address whether recombination suppression and enforced heterozygosity in regions showing absolute linkage to the S-locus results in sheltering of deleterious recessive mutations. The effect of sheltering on the prospects for the origin of new Salleles or the breakdown of self-incompatibility will be studied. The evolutionary process by which new S-alleles become integrated into the system will be addressed. An experiment designed to detect associations between the S-locus and elements influencing viability in natural populations of the horse nettle, Solanum carolinense, will be conducted. This analysis will test whether the associations among components of the self-incompatibility system predicted by theoretical work exist in natural populations.
