Following upon his productive research under a NSF Postdoctoral Fellowship in the Environmental Sciences, Dr. Paul Kores at the University of Oklahoma and the Oklahoma Biological Survey is studying the evolution of nuclear and chloroplast genes in orchids of the tribe Vanilloideae. DNA sequencing of a number of chloroplast genes has revealed apparently elevated rates of mutation (or nucleotide substitution) in orchids that grow by attaching themselves to underground root-fungus structures, known as mycorrhizae. The orchids are thought to be hemiparasites, deriving nutrition from the mycorrhizal association and conducting reduced photosynthesis. A recently proposed phylogeny or family tree for the vanilloid orchids, based on data generated by Dr. Kores and colleagues, provides a framework for estimating the number of times and the patterns or trends in which plant genes have lost function, as photosynthetic activity becomes less important in the nutritional life of the plant. Molecular evolutionary research on plants has been greatly facilitated by advances in phylogenetic research over the last several years. Detailed phylogenetic trees provide step by step insight into likely pathways of evolutionary change in both form and function. Under assumptions about relaxed functional constraints on photosynthesis, this research on plant gene evolution will explore rates and patterns of mutation in so-called parasitic and saprophytic orchids.
