A Systematic Investigation of the South African Holoparasitic Genus Hyobanche L. (Orobanchaceae)

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0089640Wolfe Parasitic plants, ones which have lost all photosynthetic ability and exist by absorbing nutrients through haustorial (usually root) connections from other nearby plants, are known in several lineages of angiosperms. Hyobanche (in the family Orobanchaceae) is one such group, a small genus of eight or so species native to southern Africa, and thought to be related to the photosynthetic genus Harveya. There is considerable confusion regarding species delimitation, abundance, host associations, and pollination for Hyobanche, which has not been studied in the field in any detail. Dr. Andrea Wolfe of Ohio State University is studying the systematics, evolution, and biology of this group of plants, by combining field collecting and observation with laboratory work on morphology and DNA sequencing to acquire new characters for phylogenetic and population-genetic analyses. Because the genus is small and is restricted in distribution to a narrow geographic region, a thorough sampling of many individuals from populations of all the species is planned. Nuclear and chloroplast gene markers are expected to provide sufficient characters for robust phylogenetic resolution of the species, in combination with morphological features. A taxonomic monograph of the genus is projected as one product of the investigation, which will include detailed geographical distributions to aid in conservation efforts. A valuable component of the project is a detailed molecular investigation of the DNA sequences and flanking regions for the chloroplast photosynthetic gene rbcL, which preliminary data suggest to be mutated into a nonfunctional "pseudogene" in these plants. Hyobanche offers an excellent system for examining in a phylogenetic context the pattern and rate of pseudogene formation following the loss of photosynthesis.