Dissertation Research: Comparing Prezygotic Isolating Mechanisms in Unimodal and Bimodal Plant Hybrid Zones.

University Of California-Irvine, Irvine CA

Investigators

Abstract

This study assesses the relative importance of ecological and genetic mechanisms that restrict natural hybridization in plants. Two closely related species of Ipomopsis plants grow in close proximity in several sites in the mountains of the western U.S. By comparing contact sites where hybrids are common with a contact site where the same two species do not hybridize successfully and instead form a bimodal distribution of morphologies, it is possible to investigate the importance of different isolating mechanisms to the rate of hybridization. Sites with low versus high frequencies of hybrids will be compared with respect to the degree of introgression of genes using molecular methods. Behavior of bird and insect pollinators will be examined at each site to test for differences in gene flow induced by behavioral choices or ability of pollinators to transfer pollen. Experimental pollinations will test for differences in the competitive ability of pollen from another species. Hybridization rates vary tremendously across different taxonomic groups. Understanding the reasons why will contribute to an understanding of the fundamental problem of how species differences and biological diversity are maintained. It could also help in predicting impacts of hybridization with genetically engineered crops or with invasive plant species.