SYSTEMATICS OF THE CALCIFIED GENERA OF THE GALAXAURACEAE (NEMALIALES,RHODOPHYTA) WITH AN EMPHASIS ON TAIWAN SPECIES1

The current separation of the calcified genera Actinotrichia Decaisne, Galaxaura Lamouroux, and Tricleocarpa Huisman et Borowitzka in the Galaxauraceae is largely based on type of life history (whether the gametophytes and tetrasporophytes are isomorphic or heteromorphic with respect to gross morphology or cortical‐cell features) and on features of postfertilization development (such as the composition of the pericarp). We reexamined the phylogenetic relationships of these genera based on comparative rbcL sequence analysis, types of life cycle, and cystocarp development. Four distinct assemblages have been identified: an Actinotrichia clade, a Tricleocarpa clade, a Galaxaura clade (containing the type species), and a Dichotomaria clade made of a number of formerly Galaxaura species (D. obtusata [Ellis et Solander] Lamarck, D. marginata [Ellis et Solander] Lamarck, and D. diesingiana [Zanardini] Huisman, Harper and Saunders). Key differences between Dichotomaria and Galaxaura include the habit of the gametophytic and tetrasporophytic generations (isomorphic in Dichotomaria and dimorphic in Galaxaura) as well as the presence or absence of a persistent pericarp in the cystocarp (present in Dichotomaria and absent in Galaxaura). Molecular data do not support monophyly for the putatively pantropical species Galaxaura rugosa, Dichotomaria obtusata, and D. marginata, all of which we conclude are in need of taxonomic revision.     

Phylogenetic study of the Nemaliales (Rhodophyta) based on large-subunit ribosomal DNA sequences supports segregation of the Scinaiaceae fam. nov. and resurrection of Dichotomaria Lamarck

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 including Actinotrichia, Galaxaura (sensu lato), and Tricleocarpa; and (iii) a new family, Scinaiaceae, segregated from the Galaxauraceae and including the genera Scinaia, Gloiophloea, Nothogenia, and probably Whidbeyella. 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 only Tricleocarpa of the Galaxauraceae. The results also show Galaxaura to be para/polyphyletic if Actinotrichia and Tricleocarpa are recognized. To remedy this, the Galaxaura marginata species complex, Galaxaura diesingiana, and Galaxaura obtusata are removed from the genus and placed in the resurrected Dichotomaria Lamarck. Galaxaura marginata, presently thought to be wide‐ranging and morphologically variable, is shown to comprise several species. As a consequence, Galaxaura tenera Kjellman and Brachycladia australis Sonder are removed from the synonymy of G. marginata and restored as independent species in Dichotomaria for 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.