9726588 Buchheim The unicellular green alga Chlamydomonas and its flagellate allies are traditionally regarded as representing the simplest of freshwater organisms. However, when one takes a closer look, these green algae are far from simple. They are diverse in morphology (for example, some species are unicellular while others form colonies), habitats (different species occur in ponds, seashores, soils, even snow), and modes of reproduction. Comparisons of DNA sequences from these algae have revealed unrecognized additional diversity, and this molecular diversity is not always consistent with perceptions of species diversity that are based on morphology. For example, in some cases, species from comparable habitats (especially those from snow) are close relatives, according to molecular sequence information; the relationship is not necessarily obvious from the appearance of the species under the microscope. In this study, Mark Buchheim will obtain new DNA sequence data from the nuclear and chloroplast genomes of green algae related to Chlamydomonas, and use these data to produce new, more informative reconstructions of the phylogenetic relationships among these algae. Dr. Buchheim will explore the taxonomic boundaries among these algae, determine to what degree habitat preferences of species are correlated with their phylogeny, and explore the relationship between history of descent and mode of reproduction. In this way, an ecological dimension will be added to studies of the taxonomy and phylogeny of these "simple" green algae.
