Grateloupia tenuisWang et Luan sp. nov. (Halymeniaceae, Rhodophyta): A New Species from South China Sea Based on Morphological Observation andrbcL Gene Sequences Analysis

Grateloupia tenuisWang et Luan sp. nov. is a new species described from Lingshui, Hainan Province, South China Sea. Based on the external form and internal structure, combined withrbcL gene sequence analysis,Grateloupia tenuisis distinct from otherGrateloupiaspecies as follows: (1) thalli is slippery and cartilaginous in texture; possess fewer branches, relatively slight main axes, and two or three dichotomous branches; (2) cortex is 5-6 layers; medulla is solid when young, but hollow in old branches; reproductive structures are dispersed in main axes of thalli and lower portions of branchlets; exhibitsGrateloupia-type auxiliary cell ampullae; (3) the four studiedG. tenuissequences were positioned in a largeGrateloupiaclade of Halymeniaceae, which included sister group generitypeG. filicinawith 68 bp differences;G. tenuiswas determined to be a sister taxon to theG. catenata,G. ramosissima,G. orientalis, andG. filiformissubclade. The pairwise distances betweenG. tenuisand these species were 39 to 50 bp. The sequences ofG. tenuisdiffered by 81–108 bp from the sequences of other samples inGrateloupia; there are 114–133 bp changes betweenG. tenuisand other genera of Halymeniaceae. In final analysis, we consideredGrateloupia tenuisWang et Luan sp. nov. to be a new species of genusGrateloupia.