Systematics of Gracilariopsis (Gracilariales, Rhodophyta) based on rbcL sequence analyses and morphological evidence

A phylogeny has been inferred from parsimony and likelihood analyses of plastid rbc L DNA sequences for seven recognized and six undescribed species of Gracilariopsis (Gp. ) (Gracilariales, Rhodophyta). New descriptions and illustrations of cystocarp morphology are provided for four Gracilariopsis species from North and South America. The generitype, Gp. sjoestedtii (Kylin) Dawson, is reinstated to include plants distributed from British Columbia to Pacific Baja California, and the name is corrected to Gp. andersonii (Grunow) Dawson. Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik is shown not to have a worldwide distribution but to be restricted to the vicinity of Peru. Gracilariopsis costaricensis is recognized with the provision that it may prove to be conspecific with Gp. lemaneiformis. Gracilariopsis lemaneiformis from North and South Carolina is described as a new species, Gp. carolinensis Liao et Hommersand sp. nov. Gracilariopsis longissima (Gmelin) Steentoft, Irvine et Farnham from Western Europe and the Mediterranean Sea and Gp. tenuifrons (Bird et Oliveira) Fredericq et Hommersand from the Ca-ribbean Sea and Brazil are recognized. Entities that have been referred to Gp. lemaneiformis from China and Japan constitute an undescribed species that is related to Gp. heteroclada Zhang et Xia. An invasive species from the Gulf of California, Mexico, and South Australia that has been assigned to Gp. lemaneiformis is resolved in a clade that includes Gp. longissima. Four undescribed species are included in the molecular analyses. The systematics of Gracilariopsis is discussed in the light of the morphological and molecular evidence.