ibclogo XVI International Botanical Congess


Abstract Number: 3910
Session = 4.15.1


PHYLOGENETIC ANALYSIS OF VOLVOCALES, USEFUL FOR COMPARATIVE GENETIC STUDIES


Annette W. Coleman. Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912, USA


The family Volvocaceae, colonial green flagellates, has long piqued the curiosity of evolutionists. In part, this is because members of the family share in common a unique developmental alteration in cell arrangement akin to gastrulation, and an alternative evolutionary path toward the multicellular state. Prior comparisons of ribosomal RNA gene sequences, and those of RUBisCO large subunit have seriously questioned whether accepted genera and species, as well as the family itself, are monophyletic. Sequences of the internal transcribed repeats of the nuclear rDNA repeat regions from >300 different isolates of the family Volvocaceae now suggest that the family Volvocaceae is divided into three parts. The first consists of Astrephoneme and two clades of Gonium species. The second contains all the syngens of Pandorina morum, with the species of Volvulina interspersed. The final grouping includes all the oogamous organisms plus one clade of anisogamous forms, Yamagisiella. In this grouping, some Volvox species plus Platydorina branch basally while the remaining Volvox species fall among the various Eudorina and Pleodorina species. No evidence for close relationship with any green flagellate species other than Chlamydomonas reinhardtii was found.


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