A comparative study of the red alga Grateloupia filicina (Halymeniaceae) from the northwestern Pacific and Mediterranean with the description of Grateloupia asiatica, sp nov.

Morphological observations and molecular analyses of the red alga Grateloup ia filicina (Halymeniaceae) from two geographically distant regions, easter n Asia (Japan and northern China) in the northwestern Pacific and Italy in the Mediterranean, reveal the presence of two distinct entities. Morphologi cally, the eastern Asian entity differs substantially from the Italian enti ty in the following ways: 1) thin and soft thalli with wider axes, 2) dense r medullary filaments, 3) scattered reproductive structures over the entire thallus, and 4) a mature auxiliary cell that is oval and slightly larger t han other ampullary cells. Phylogenetic analysis based on the ribulose-1,5- bisphosphate carboxylase/oxygenase gene (rbcL) sequences revealed that the eastern Asian and Italian entities are phylogenetically far apart, strongly supporting the differentiation of these two entities at the species level. The eastern Asian entity is therefore described as a new species, Gratelou pia asiatica. This species can be distinguished from most known species of Grateloupia that have widely flattened thalli by its compressed to narrowly flattened axes with numerous pinnate proliferations and from a few species with similar thalli by a particular combination of features, including a g elatinous texture, mostly simple and narrower axes, a thinner cortex, and t he absence of catenate proliferations.