RESEARCH ON THE REVISION OF GRATELOUPIA DIDYMECLADIA LI ET DING BASED ON MORPHOLOGICAL OBSERVATIONS AND MOLECULAR ANALYSES

With the combination of morphological observation and rbcL (ribulose-1, 5-bisphosphate carboxylase/oxygenase) and COⅠ (Partial cytochrome c oxidaseⅠ) gene sequence analyses, eleven samples of G. didymecladia Li et Ding, collected from Shantou, Wenzhou and Dalian in China, were re-examined. The results indicated that: (1) the thalli were characterized as solitary or caespitose habit, in red-brown or dark-red color, fleshy and gelatinous in texture; they became cartilaginous at an older age with the height of 15—50 cm. The flattened main axes were erect, 3—15 mm in width, 1 mm in thickness, pinnately branched 1—3 times, bearing abundant branches with opposite or alternated arrangement. The end portion of the main axes was tapering. Numerous proliferous branchlets were on the surface and margin of the main axes, constricted at the base, of various lengths reaching as long as 15 cm; Gametophytes dioecious, the samples had five-celled carpogonial branches and four-celled auxiliary branches (5cpb-4auxb model), they are typi-cal Grateloupia-type. Tetrasporangia were formed from the inner cortex cells, cruciately divided. These morphological features were the same as G. subpectinata Holmes. (2) According to the phylogenetic tree constructed by rbcL gene sequences, the eleven G. didymecladia sequences in this study had no pairwise divergence and formed a single monophyletic subclade. Intraspecific divergence exists between the eleven samples and G. subpectinata from Korea and Japan, ranged from 1 bp (0.08) to 2 bp (0.17%). According to the phylogenetic tree constructed by COⅠgene sequences, the eleven sequences were identical and formed a single monophyletic subclade. The pairwise distance of COⅠsequences between the samples and G. subpectinata from Korea was 1 bp (0.18%), also belonging to intraspecific difference. G. didymecladia and G. subpectinata were demonstrated to be the same species based on the morphological observation and molecular analysis. Based on the priority rule, G. didymecladia was classified as the synonym of G. subpectinata. This is to date the first discovery of G. subpectinata existing in China, indicating a new record species.