TAXONOMY AND PHYLOGENY OF OSMUNDEA (RHODOMELACEAE, RHODOPHYTA) IN ATLANTIC EUROPE

Abstract

Two species of Osmundea Stackhouse (Rhodomelaceae, Rhodophyta) that occur in Atlantic Europe have been confused under the names Osmundea ramosissima (Oeder) Athanasiadis and Osmundea truncata (Kützing) Nam et Maggs, regarded until now as a synonym of O. ramosissima. An epitype from its type locality (Stavanger, Norway) is selected for Osmundea ramosissima Athanasiadis, recognized here as a valid name for Fucus ramosissimus Oeder, nom. illeg. Details of vegetative and reproductive morphology of O. ramosissima are reported, based on material from France, the British Isles, and Helgoland. Osmundea ramosissima resembles other species of Osmundea in its vegetative axial segments with two pericentral cells and one trichoblast, spermatangial development from apical and epidermal cells (filament type), the formation of five pericentral cells in the procarp-bearing segment of the female trichoblast, and tetrasporangial production from random epidermal cells. Among the species of Osmundea, O. ramosissima is most similar to O. truncata. Both species have discoid holdfasts, secondary pit connections between epidermal cells, and cup-shaped spermatangial pits. They differ in that: (a) O. ramosissima lacks lenticular wall thickenings and refractive needle-like inclusions in medullary cells, both of which are present in O. truncata; (b) O. ramosissima has branched spermatangial filaments that terminate in a cluster of several cells, whereas in O. truncata the unbranched spermatangial filaments have a single large terminal sterile cell; and (c) cystocarps of O. ramosissima lack protuberant ostioles but ostioles are remarkably protuberant in O. truncata. Phylogenetic analyses of rbcL sequences of Laurencia obtusa (Hudson) Lamouroux and all five Atlantic European species of Osmundea, including the type species, strongly support the generic status of Osmundea. Osmundea ramosissima and O. truncata are closely related (5.2% sequence divergence) and form a well-supported clade sister to a clade consisting of O. pinnatifida (Hudson) Stackhouse, O. osmunda Stackhouse and O. hybrida (A. P. de Candolle) Nam. The formation of secondary pit connections between epidermal cells is a synapomorphy for the O. ramosissima+O. truncata clade. The close relationship between species with cup-shaped spermatangial pits (Osmundea hybrida) and urn-shaped pits (Osmundea pinnatifida and Osmundea osmunda) shows that spermatangial pit shape is not an important phylogenetic character. Parsimony analysis of a morphological data set also supports the genus Osmundea but conflicts with the molecular trees in infrageneric relationships, placing O. hybrida basal within the Osmundea clade and grouping O. osmunda and O. pinnatifida but not O. truncata and O. ramosissima. A key to Osmundea species is presented.

Redefining the taxonomic status ofLaurencia dendroidea(Ceramiales, Rhodophyta) from Brazil and the Canary Islands

“…This complication is reflected by the large number of species and infraspecific taxa that have been assigned to the complex: Guiry & Guiry (2011) list 430 taxa but consider only 134 to be currently accepted taxonomically. The use of molecular markers has proved to be useful in delimiting taxa and inferring their phylogenetic relationships, and has corroborated the current generic classification (Nam et al, 2000;McIvor et al, 2002;Abe et al, 2006;Fujii et al, 2006;Dı´az-Larrea et al, 2007;Gil-Rodrı´guez et al, 2009;Martin-Lescanne et al, 2010;Rocha-Jorge et al, 2010;Sentı´es et al, 2011).…”

Overview of the taxonomy and of the major secondary metabolites and their biological activities related to human health of the Laurencia complex (Ceramiales, Rhodophyta) from Brazil

“…Many species have no defined taxonomic boundaries and present extensive morphological plasticity, making their taxonomic delimitation difficult. In this context, the use of molecular markers has proven to be useful for delimiting the taxa and inferring their phylogenetic relationships and has corroborated the current classification system (Nam et al, 2000;McIvor et al, 2002;Abe et al, 2006;Fujii et al, 2006;Díaz-Larrea et al, 2007;Cassano et al, 2009;Gil-Rodríguez et al, 2009;Martin-Lescanne et al, 2010;Rocha-Jorge et al, 2010).…”

The marine macroalgae of Helgoland (North Sea): an annotated list of records between 1845 and 1999

“…Osmundea ramosissima Maggs and Hommersand (1993) reported Laurencia truncata Kützing from Helgoland, which was recently transferred to O. ramosissima (Nam et al 2000). Their decision was based on two specimens in the herbarium at Lund, one undated and probably collected by Binder, the other by David Hylmö in July 1922, both with a discoid base and secondary pit connections.…”