The role of hybridization and polyploidy in plant evolution

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Hybridization (interbreeding of species) and polyploidy (chromosome doubling) are widespread phenomena in the flowering plants. Together they lead to new combinations of traits that can become stabilized as new allopolyploid species, with fundamental consequences for plant evolution. This is often of practical importance, for example when assessing the taxonomic status of rare species or the consequences of interbreeding between crop plants and related weeds. It is therefore important to understand how polyploid hybrids arise and evolve. This work focuses on the importance of hybridization in two distinct plant groups, fawn-lilies (Erythronium) and North American asters (Symphyotrichum). Evolutionary relationships are well understood in these groups, allowing hybrids to be readily detected using molecular tools. This project makes use of DNA sequence data from specific chloroplast and nuclear gene regions that give fine-scale resolution of relationships. It has several components: (1) phylogenetic analyses and detection of hybridization (especially leading to polyploid hybrids) in these groups; (2) determination of hybrid frequency and parentage; and (3) investigation of the genetic characteristics of allopolyploids, including changes in duplicated genes, by comparison of natural allopolyploid species with their parent species and by synthesis of artificial hybrids from the same parents. This work will enhance understanding of the ways in which new genetic forms are created and maintained in plants.