PHYLOGENY OF THE BATRACHOSPERMALES (RHODOPHYTA) INFERRED FROM RBCL AND 18S-RIBOSOMAL DNA GENE-SEQUENCES

The sequence data from the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene and 18S ribosomal DNA (small subunit ) of taxa in the freshwater rhodophyte order Batrachospermales were us ed to construct phylogenetic hypotheses. Taxa examined in this study r epresent four families, eight genera, and six sections of the genus Ba trachospermum. In addition, Rhododraparnaldia oregonica Sheath, Whitti ck et Cole, was included in the analysis because it shares particular ultrastructural, reproductive, and morphological characteristics with members of the Batrachospermales and Acrochaetiales. The trees generat ed from each gene, as well as a combined data set, were largely congru ent. Rhododraparnaldia consistently occurs on an early branch within t he Acrochaetiales-Palmariales clade and does not appear to be a member of the Batrachospermales. In addition, Thorea violacea Bory de St. Vi ncent was not closely related to the other taxa of the Batrachospermal es in all trees and hence the family Thoreaceae does not appear to be a natural grouping within this order. All other taxa analyzed, which a re presently classified within this order, formed a monophyletic clade in most analyses. Psilosiphon scoparium Entwisle was not closely alli ed with the taxa of the Lemaneaceae, lending support to the newly prop osed family Psilosiphonaceae. Sequence data from the remaining taxa of the Lemaneaceae support the concept of a derived monophyletic clade. The genus Batrachospermum appears to comprise many morphologically sim ilar but distantly related taxa, which will need further investigation to resolve their taxonomic status. Tuomeya, Sirodotia and Nothocladus are retained at the generic level until further data are obtained.