Molecular Systematics of the Zygnematales

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Zygnematales is the most diverse member of the green algae with about 7,000 species in 55 genera. Current hypotheses of phylogenetic relationships among the green plants places this order as the sister taxon of the higher plants. However, phylogenetic relationships among the members of Zygnematales are problematic. This results in part because the individuals are subject to considerable morphological modification contingent upon the environment in which they occur and upon the chromosome number which is highly plastic. The PIs propose to examine genes that are not subject to such fluctuations in order to develop a phylogenetic model for this order of algae. The derived model should have implications for the origin and radiation of the land plants and the factors that may have played a role in the occupation of terrestrial habitats. The genes to be considered are all located in the chloroplast. This suite of genes has proven useful in elucidating the phylogenies of a variety of land plant groups. Therefore, the data set produced by the PIs can be directly applied to comparisons of all other green plants.