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 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]