Saunders, Gary W.

This review discusses the impact that molecular studies of the genic and spacer regions of the ribosomal cistron have had on the systematics and classification of the florideophyte red algae. Each ribosomal cistron consists of a non- transcribed spacer region (NTS), an external transcribed spacer region (ETS), the small-subunit (SSU) rRNA gene, internal transcribed spacer (ITS 1) region 1, the 5.8S rRNA gene, internal transcribed spacer (ITS 2) region 2, and the large-subunit (LSU) rRNA gene. To date, molecular investigations on the Rhodophyta that utilize the ribosomal cistron have been based largely on the SSU and, to a lesser extent, the ITS regions. We then outline the methods and procedures we use to obtain sequence data from the various regions of the ribosomal cistron. A discussion of recent advances in florideophyte systematics within the four florideophyte lineages outlined by Saunders & Kraft (1997) is presented. We then close the review with an introduction to, and discussion of the potential utility of sequences of the LSU for resolving relationships within the Rhodophyta.

Callophyllis is the largest genus in the red algal family Kallymeniaceae and includes over 50 described species. Since its description, there has been considerable debate over the circumscription of this genus relative to related genera. Specifically, the genus Euthora has sometimes been placed in synonymy with Callophyllis , and a number of species of Pugetia have been transferred to Callophyllis. Phylogenetic analyses based on sequences of nuclear large-subunit ribosomal DNA for representatives of the Kallymeniaceae were completed to assess the various taxonomic proposals surrounding Callophyllis , Euthora and Pugetia . Results indicate that the genus Callophyllis (as generally recognized) is polyphyletic. Callophyllis cristata occupies a position in the trees separate from the remainder of Callophyllis species (including the type Callophyllis variegata ), supporting recognition of Euthora as a distinct genus. Callophyllis chilensis and Callophyllis firma group with the type species of Pugetia , Pugetia fragilissima , thus confirming an earlier taxonomic decision to include these species in the latter genus. A discussion of the relative merits of various reproductive versus vegetative features for assigning species among these three genera is provided. Though outside the scope of the current study, relationships among species of Callophyllis sensu stricto must be visited in light of the results. Although the remaining six species of Callophyllis included in the present trees unequivocally form a monophyletic group, two isolates identified as Callophyllis pinnata (from California and Chile) do not group together, illustrating the confusion generated from the morphological variation within this genus. [ABSTRACT FROM AUTHOR]

Gene sequence data have been newly obtained for 18 species in 13 genera of the order Nemaliales (Rhodophyta), allowing for the first time a relatively comprehensive molecular phylogenetic appraisal of the order. The phylogenetic trees generated from these data support the recognition of three families: (i) the Liagoraceae as presently constituted; (ii) a reduced Galaxauraceae includingActinotrichia,Galaxaura (sensu lato), andTricleocarpa; and (iii) a new family, Scinaiaceae, segregated from the Galaxauraceae and including the generaScinaia,Gloiophloea,Nothogenia, and probablyWhidbeyella. The four genera of the Scinaiaceae differ from the newly circumscribed Galaxauraceae in being uncalcified, and having heteromorphic life histories in which the tetrasporophyte is much reduced and filamentous or crustose. This type of life history is found in onlyTricleocarpaof the Galaxauraceae. The results also showGalaxaurato be para/polyphyletic ifActinotrichiaandTricleocarpaare recognized. To remedy this, theGalaxaura marginataspecies complex,Galaxaura diesingiana, andGalaxaura obtusataare removed from the genus and placed in the resurrectedDichotomariaLamarck.Galaxaura marginata, presently thought to be wide-ranging and morphologically variable, is shown to comprise several species. As a consequence,Galaxaura teneraKjellman andBrachycladia australisSonder are removed from the synonymy ofG. marginataand restored as independent species inDichotomariafor South African and Australian isolates, respectively. The Liagoraceae is shown to encompass genera previously placed in the segregate families Nemaliaceae and Dermonemataceae, and the value of the reproductive characters used to define those taxa is discussed. [ABSTRACT FROM AUTHOR]

The phylogenetic relationship among 12 previously described batrachospermalean taxa and a novel member of the order were investigated using the LSU and rbcL genes separately and in combination. The primary goal of this research was to establish the phylogenetic placement of a previously undescribed freshwater red alga from Chile. The results showed that the new entity with pseudoparenchymatous tube morphology is a member of the Batrachospermales and Petrohua bernabei gen. et sp. nov. is described herein. This is the first record to our knowledge of a Lemanea-like alga from Chile. It would appear that this thallus construction has evolved at least three times in the Batrachospermales and that the switch from a Batrachospermum-like construction to a pseudoparenchymatous construction may be a repeated adaptive response to turbulent waterfall habitats. In addition to providing information about a new freshwater red alga, this study sought to determine whether combining the data from two genes would produce a more robust phylogeny, particularly for intermediate nodes, to resolve familial relationships within the order. As with previous analyses, the Batrachospermales was resolved as a clade and support was high for relationships resolved among relatively recent nodes. Unfortunately, combining the LSU and rbcL data did not have the desired effect of more fully resolving intermediate nodes among the Batrachospermales. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]