Brigitte Gavio

SYSTEMATICS OF GRATELOUPIA FILICINA (HALYMENIACEAE, RHODOPHYTA), BASED ON rbcL SEQUENCE ANALYSES AND MORPHOLOGICAL EVIDENCE, INCLUDING THE REINSTATEMENT OF G. MINIMA AND THE DESCRIPTION OF G. CAPENSIS SP. NOV.

Grateloupia filicina (C. Agardh) Lamouroux, originally described from the Mediterranean Sea, has long been considered a textbook example of a marine red alga with a cosmopolitan distribution. An rbcL‐based molecular phylogeny, encompassing samples covering the entire geographic distribution of the species, revealed a plethora of “cryptic” species, whereby the presence of genuine G. filicina is limited to the Mediterranean basin. The phylogeny revealed a strong biogeographic imprint, with specimens from temperate regions resolved in clades composed of species inhabiting the same geographic region. Presence of widely divergent morphologies in the temperate clades indicated that several lineages have converged independently to a G. filicina‐type morphology. Tropical representatives are resolved in a single clade with very uniform G. filicina‐type morphology and pairwise sequence divergences that are lower than the average divergence observed in temperate lineages. This, combined with a lack of clear geographic structure among the tropical lineages, may indicate a more recent divergence with long‐range dispersal capacities. Violations to the biogeographic signal in temperate lineages seemed to be due to either inadequate taxonomy or recent introductions. Grateloupia minima P. & H. Crouan, a taxon placed in synonymy under G. filicina, is reinstated as a separate species distributed in the northeast Atlantic Ocean. Grateloupia capensis sp. nov. is described to accommodate specimens from South Africa with a G. filicina‐type morphology, and G. filicina var. luxurians is elevated to species status. Morphological and anatomical characters were put forward that support the distinctiveness of these three distinct species.

Systematic reassessment of the red algal genus Phyllymenia (Halymeniaceae, Rhodophyta)

A systematic reassessment of the sole representative of the South African genus Phyllymenia, P. belangeri, indicates a lack of clear-cut diagnostic characters to separate it from Grateloupia. The morphology of the auxiliary cell ampullae, widely regarded as a key generic character in the Halymeniaceae, is almost identical in both genera. The autapomorphic character that has traditionally separated Phyllymenia from Grateloupia is the formation of pronounced lateral cytoplasmic protuberances on inner cortical cells. However, the establishment of protuberances is correlated with the presence of large intercellular spaces between neighbouring cortical cell files, coupled with narrow intercalary cortical cells. Thus, in order to establish secondary pit connections to more distant neighbouring cells, cortical cell protuberances may have become more prominent in P. belangeri than in species of Grateloupia with smaller intercellular spaces. Phylogenetic analyses of chloroplast-encoded rbcL sequences for a dataset including four representatives of P. belangeri and 32 other species, currently placed in Grateloupia or Prionitis, resolve (with high support) P. belangeri as a sister taxon of G. longifolia from South Africa. Based on morphological and molecular evidence, it is therefore proposed that Phyllymenia be reduced to a synonym of Grateloupia.

Grateloupia huertana sp. nov. (Halymeniaceae, Rhodophyta), a peculiar new prostrate species from tropical Pacific Mexico

L.E. Mateo-Cid, A.C. Mendoza-González, B. Gavio and S. Fredericq. 2004. Grateloupia huertana sp. nov. (a peculiar new prostrate species from tropical Pacific Mexico. Phycologia 44: 4–16. Grateloupia huertana sp. nov. is newly described from Oaxaca, Pacific Mexico on the basis of comparative morphology and rbcL sequence analysis. It is distinguished from other Grateloupia species by its entirely prostrate, fleshy-cartilaginous, highly polymorphic habit ranging from single, irregularly spreading and perforated lobes with marginal proliferations, to rosette-like clumps of overlapping blades up to 5 cm in diameter. The entire lowermost surface acts as a single expanded holdfast conforming to the topography of the substratum. Globose and deeply immersed cystocarps are scattered and restricted to the dorsal side. Auxiliary cell and carpogonial ampullae are of the simple Grateloupia-type. The medulla varies from compact and cellular to a network of predominantly periclinal filaments producing varying degrees of secondary cells as the thallus expands laterally. The new species is embedded within the Grateloupia clade in rbcL trees, but its phylogenetic position in relation to other members of the genus remains equivocal. A systematic revision of Grateloupia sensu lato is called for.