A new species Lobophora tsengii sp. nov. (Dictyotales; Phaeophyceae) from Bach Long Vy (Bailongwei) Island, Vietnam.

A new species Lobophora tsengii is described from Bach Long Vy (Bailongwei) Island, Haiphong Province, Vietnam. The plants inhabit the subtidal zone and have predominantly erect fan-shaped thalli that attach to the substrate by a basal holdfast. The thallus is commonly composed of a single layer of large medullary cells with four layers of cortical cells on either side of the medulla. The newly collected specimens from the island are morphologically similar to those from Hainan Island, China, but differ from the New Caledonian ones in having thicker thallus. In molecular phylogenetic analyses based on concatenated rbcL and cox3 sequences, the specimens from the island were 100% identical to those from Hainan Island, China, and they formed a clade separating from other Lobophora species. Additionally, based on analyses of numerous cox3 sequences, our specimens were also distinguished from the closely related taxa occurring in New Caledonia, Kenya, and West Australia. Combining the morphological and molecular analyses, we conclude that our specimens represent a new species of Lobophora, which is apparently endemic to the Beibu Gulf (Gulf of Tonkin) and adjacent waters. [ABSTRACT FROM AUTHOR]