MOLECULAR SYSTEMATICS OF THE FLORIDEOPHYCEAE (RHODOPHYTA) USING NUCLEAR LARGE AND SMALL SUBUNIT rDNA SEQUENCE DATA

Abstract

Sequence data are presented for approximately 85% of the nuclear large subunit (LSU) rDNA gene for one member of the Bangiophyceae and 47 members of the Florideophyceae, the latter representing all but one of the currently recognized florideophyte orders. Distance, parsimony, and maximum likelihood analyses of these data were used to generate phylogenetic trees, and bootstrap resampling was implemented to infer robustness for distance and parsimony results. LSU phylogenies were congruent with published nuclear small subunit (SSU) rDNA results in that four higher level florideophyte lineages were resolved: lineage 1, containing the order Hildenbrandiales; lineage 2, recovered only under distance analysis, composed of the orders Acrochaetiales, Balliales, Batrachospermales, Corallinales, Nemaliales, Palmariales, and Rhodogorgonales; lineage 3, containing the Ahnfeltiales; and lineage 4, composed of the orders Bonnemaisoniales, Ceramiales, Gelidiales, Gigartinales, Gracilariales, Halymeniales, Plocamiales, and Rhodymeniales. Analyses were also performed on a combined LSU–SSU data set and an SSU‐only data set to account for differences in taxon sampling relative to published studies using this latter gene. Combined LSU–SSU analyses resulted in phylogenetic trees of similar topology and support to those obtained from LSU‐only analyses. Phylogenetic trees produced from SSU‐only analyses differed somewhat in particulars of branching within lineages 2 and 4 but overall were congruent with the LSU‐only and combined LSU–SSU results. We close with a discussion of the phylogenetic potential that the LSU has displayed thus far for resolving relationships within the Florideophyceae.

Combining small and large subunit ribosomal DNA genes to resolve relationships among orders of the Rhodymeniophycidae (Rhodophyta): recognition of the Acrosymphytales ord. nov. and Sebdeniales ord. nov.

“…Molecular investigations have consistently resolved most orders of the Rhodymeniophycidae as monophyletic, with the Gigartinales being a notable exception in both SSU-only and LSU-only (Harper & Saunders, 2001b) analyses. However, phylogenies based on these genes have largely failed to resolve relationships among the included orders.…”

“…These were imported into SeqPup, a multiple alignment software program (Gilbert, 1995), and aligned to existing red algal SSU and LSU (Harper & Saunders, 2001b) alignments as appropriate. Three initial alignments were constructed: (1) SSU only, (2) LSU only and (3) SSU þ LSU combined.…”

“…The lack of resolution in the initial combined SSU þ LSU phylogenies of Harper & Saunders (2001b), in addition to the conflicting ordinal relationships relative to extensive SSU-only studies, may have been the result of low taxon sampling and/or attraction artefacts. To test this hypothesis, and in an effort better to resolve relationships among orders of the Rhodymeniophycidae, we have developed a more extensive combined SSU þ LSU alignment to assess phylogeny in this subclass.…”

“…Harper & Saunders (2001b) speculated that the LSU might provide resolution among orders of the Rhodymeniophycidae where the SSU had failed because of its greater length and proportion of variable sites. As with SSU alone, however, combined SSU þ LSU analyses recovered the Rhodymeniophycidae as monophyletic, but failed to resolve relationships among its orders.…”

Ultrastructure of auxiliary and gonimoblast cells during carposporophyte development in the red alga Cryptopleura ruprechtiana (Delesseriaceae, Ceramiales, Rhodophyta)

“…Pit-plug ultrastructure in combination with molecular data have led to a considerable restructuring of red algal classification at the ordinal level (Pueschel and Cole, 1982;Pueschel, 1989;Harper and Saunders, 2001). However, recent molecular systematic studies have not dealt with the taxonomic levels of families or genera and taxa within the families.…”