对枝蜈蚣藻的修订研究——基于形态特征和基因序列分析

通过形态观察结合rbcL和COⅠ基因序列分析的方法, 对采自广东省汕头市、浙江省温州市和辽宁省大连市的对枝蜈蚣藻Grateloupia didymecladia Li et Ding的11个标本进行了重新鉴定。结果表明: (1)藻体单生或丛生, 红褐色或深红色, 质地黏滑、肉质、衰老时软骨质, 成熟藻体直立, 高15—50 cm, 主枝明显, 扁平, 宽3—15 mm, 厚约1 mm, 末端渐尖, 1—3回羽状分枝。小枝对生或互生, 生长在主枝上或主枝边缘, 基部缢缩, 长短不一, 最长可达15 cm; 配子体为雌雄异体, 果胞枝生殖枝丛和辅助细胞生殖枝丛均为Grateloupia型, 果胞枝生殖枝丛主枝由5个细胞组成, 辅助细胞生殖枝丛主枝由4个细胞组成(5cpb-4auxb型); 四分孢子囊由四分孢子体的内皮层细胞产生, 呈十字形分裂。以上特征均与亚栉状蜈蚣藻G. subpectinata Holmes一致。(2)基于rbcL基因序列构建的系统树显示, 11个样本之间无碱基差异, 形成独立的进化支, 与产于韩国和日本的亚栉状蜈蚣藻G. subpectinata Holmes碱基差异分别为1 bp (0.08%)和2 bp (0.17%), 属于种内差异; 基于COⅠ基因序列构建的系统树显示, 11个样本之间无碱基差异, 形成独立的进化支, 与韩国产的亚栉状蜈蚣藻碱基差异为1 bp (0.18%), 属于种内差异。根据形态、结构及基因序列分析, 确定对枝蜈蚣藻与亚栉状蜈蚣藻为同一种, 根据优先法则, 将对枝蜈蚣藻G. didymecladia Li et Ding作为亚栉状蜈蚣藻G. subpectinata Holmes的同物异名。亚栉状蜈蚣藻为中国新记录种。

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.