Molecular Evolution of Anthocyanin Pathway Genes in Morning Glories (Ipomoea)

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Most investigations of molecular evolution examine single genes, without respect to their interactions with other genes. However, most genes do not act in isolation, but interact with many other genes, which are likely to influence each other's evolution. One goal of this project is to determine whether and how such interactions actually cause predictable variation among genes in their rates of evolution. Specifically, genes of the anthocyanin pigment pathway in morning glories (genus Ipomoea) will be examined to determine whether observed evolutionary rate variation is due to differences in selective constraint (i.e. whether genes downstream in the pathway are less subject to purifying natural selection because they influence fewer characters). A second goal of this project is to begin examining the relative importance of regulatory and structural genes in adaptive divergence between species by determining the molecular basis of phenotypic divergence. The long-term goal of this project is to examine a large number of species whose color pattern has diverged from the presumed ancestral type of cyanidin-based blue/purple pigmentation throughout the corolla limb and throat. For each species the relative contribution of structural and regulatory genes to divergence will be determined. However, the current objective is more limited: to characterize the genetic changes that have resulted in the production of white flowers by two species, I. alba and I. igualensis. Initially, investigation will concentrate on these two species to demonstrate the feasibility of the proposed approach.