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

Abstract

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.

Estimates of nuclear DNA content in red algal lineages

“…Molecular systematic investigations have resolved a close relationship among members of the Acrochaetiales, Palmariales, Colaconematales and Nemaliales (Saunders et al 1995; Harper and Saunders 2002; Huisman et al 2004), which are considered to represent early lineages of florideophytes. The transfer of Rhodothamniella floridula (Dillwyn) Feldmann from the Acrochaetiales (Saunders et al 1995) and segregation of the Colaconematales (Harper and Saunders 2002) has resulted in a monophyletic Acrochaetiales that is sister to the Palmariales (e.g.…”

Phylogenetic relationships of Dichotomaria (Nemaliales, Rhodophyta) with the proposal of Dichotomaria intermedia (R.C.Y. Chou) comb. nov.

“…Our analysis of rbcL and cox1 sequences from numerous specimens of Dichotomaria from the Indo-Pacific, Reference Taylor 1945 This study Huisman andBorowitzka (1990), Huisman (2006) This study Huisman and Womersley (1994), Wang et al (2005) This study Taylor (1960) This study Huisman et al (2004) This study…”

“…Ellis et Solander (Ellis and Solander 1786). Dichotomaria is currently characterized by its life history with alternating isomorphic gametophytic and tetrasporophytic phases, the presence of a pericarp enclosing the cystocarp, a multinucleate fusion cell formed by incorporation of gonimoblast initials and inner gonimoblast cells, and cruciate tetrasporangia produced on stalk cells (Huisman et al 2004, Wang et al 2005, Huisman 2006, Kurihara and Huisman 2006). Subsequent analyses of plastid rbcL sequences strongly supported Dichotomaria as a distinct genus (Wang et al 2005, Liu et al 2013.…”

“…The majority of species were transferred from Galaxaura (Huisman et al 2004, Kurihara et al 2005, Wynne 2005, 2011, Kurihara and Huisman 2006, while Dichotomaria hommersandii S.L. Liu et S.M.…”

“…Dichotomaria Lamarck (1816), one of four calcified genera in the family Galaxauraceae, was resurrected by Huisman et al (2004) on the basis of molecular and morphological evidence. The generitype is Dichotomaria marginata (J. Ellis et Solander) Lamarck from the Bahamas, with the basionym Corallina marginata J.…”