Phylogeny,species diversity and biogeographic patterns of the genus Tricleocarpa (Galaxauraceae,Rhodophyta) from the Indo-Pacific region,including T. confertus sp. nov. from Taiwan

Among four different genera in Galaxauraceae, species diversity of the genus Tricleocarpa Huisman & Borowitzka is underestimated and requires further examination. In this study, we explored a molecular phylogeny of Tricleocarpa with an emphasis on Taiwan species and reassessed species diversity of the genus from the Indo-Pacific region based on analyses of rbcL and COI-5P sequences and morphological observations. The molecular analyses showed that species of Tricleocarpa examined are grouped into seven clades: six clades in the T. cylindrica group (the T. cylindrica complex, T. confertus, T. jejuensis, T. natalensis and two uncharacterized T. ‘cylindrica’ clades) and one clade as the T. fragilis group. Overall, at least 12 species in Tricleocarpa were detected from the Indo-Pacific region, including a new species, T. confertus S.-L. Liu & S.-M. Lin, from Taiwan. Among them, T. confertus can be separated from other species of Tricleocarpa by a thallus consisting of dichotomous or trichotomous, articulated and moniliform branches with smooth surfaces, constrictions at nodes and slightly anti-triangular in shape. The cystocarp morphology of T. confertus is similar to the T. cylindrica group by having paraphyses intermixing with gonimoblast filaments. Recognition of this new species from other species is also supported by the DNA-based, algorithmic species delimitation approaches. With the combination of molecular phylogeny and species diversity reassessment, our phylogeographic analysis supported a trend that species in the T. fragilis group are restricted in their distribution to subtropical and tropical areas whereas species in the T. cylindrica group have a wide distribution, ranging from temperate through to tropical areas.     

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.     

Further observations on the genus Pappomonas Manton et Oates with special reference to P. virgulosa sp. nov. from West Greenland

Electron microscopy of dried preparations of Arctic nanoplankton has permitted a second species of the recently erected genus Pappomonas Manton et Oates to be described and named. P. virgulosa sp. nov. is characterised by coccolith appendages composed of a central shaft ending in a cluster of four finger-like rods. There are also calcified plates of characteristic construction, without appendages. Detailed observations on the coccoliths, especially on the shapes and arrangement of component calcite crystallites and the presence of unmineralised components, have permitted further comparisons to be made with equivalent structures in Papposphaera lepida Tangen, recently investigated in the southern hemisphere, as well as with Pappomonas flabellifera Manton et Oates. As a working hypothesis, an interpretation of coccolith morphology in all three taxa has been formulated in terms of known structural components of uncalcified scales in Chrysochromulina spp. The need for fuller information on certain details, notably the coccolith bases in Pappomonas spp. is stressed.