Characterization of Gracilaria vieillardii (Gracilariaceae, Rhodophyta) and molecular phylogeny of foliose species from the western Pacific Ocean, including a description of G. taiwanensis sp nov.

Gracilaria vieillardii has been widely reported from the western Pacific Ocean; however, these records remained provisional due to the absence of morphological details for material from the type locality, New Caledonia. To clarify the taxonomic position of G. 'vieillardii' from Taiwan and the interspecific relationships of the foliose Gracilaria species from the western Pacific Ocean, we used rbcL sequences and inferred their molecular phylogeny along with that of other foliose species from around the world. Foliose species with textorii-type spermatangial conceptacles, collected from the western Pacific Ocean, were analyzed here along with foliose species from South Africa. These formed a natural assemblage. In contrast, those foliose species with textorii-type spermatangial conceptacles, which were collected from the tropical Atlantic Ocean, did not form a monophyletic clade. We described Gracilaria taiwanensis sp. nov., based upon a foliose species with marginal teeth, that was previously recorded from Taiwan as G. vieillardii Our molecular analyses indicated that G. taiwanensis was sister to the clade of G. vieillardii from the type locality, New Caledonia; however, they differed by 28 base pairs among 1390 aligned nucleotides of the rbcL gene. Gracilaria taiwanensis was characterized by its palmate, prostrate thallus and thicker cystocarp floor (180-300 mu m thick). In contrast, G. vieillardii possessed bushy, slightly prostrate thalli, and the cystocarp floor was not as thick (100-150 mu m thick).