XVI International Botanical Congess

Sequences of the ribosomal cistron have been useful as molecular tools for inferring organismal phylogenies. Within the Rhodophyta, sequences of the small-subunit have had the greatest impact at the ordinal level. However, now that virtually all known lineages of red algae have been explored, a number of relationships remain unresolved. Our focus is now on the potential of sequences from the large-subunit (LSU) for addressing the phylogenetics of the Rhodophyta. The LSU is quite large and possesses a number of regions of varying divergence. These features should provide the resolution not obtained from more conservative molecular data sets. At present we have generated sequence data for ca. 80% of the LSU for over 35 members of the Rhodophyta, spanning virtually all the recognized florideophyte orders. Comparative SSU and LSU phylogenies will be presented, a critical evaluation of the LSU as an informative molecular tool will be given, and future directions for LSU research will be discussed.