Phylogeny and Geographical Derivation of Genus Hildenbrandia Based on Morphological and Molecular Evidence

The marine and freshwater Hildenbrandia samples were collected from diverse locations of China and Japan,and mor-phological characterization and molecular phylogenetic analysis were conducted on these samples.Morphological measurements of freshwater specimens were consistent with the results of H.jigongshanensis,whereas cell dimensions of marine specimens were slightly larger than those of widely distributed H.rubra and H.crouanii.Phylogenetic trees based on rbcL,psbA and UPA sequences were consistent.Freshwater specimens collected in this study formed an independent clade with H.jigongshanensis supported by high values.Species attribution was confirmed further by the similar ITS2 secondary structures among the samples of H.jigongshan-ensis.It was found that the intraspecific divergence of rbcL gene in H.jigongshanensis was smaller than other two freshwater species H.rivularis and H.angolensis.Phylogenetic trees showed that marine specimens in this study grouped together with H.rubra samples of North America,and were different with the H.rubra samples of Europe.Combining the comparison results of CBC numbers in ITS2 secondary structure,we propose the marine samples collected in this study to be a new species Hildenbrandia qingdaoensis sp.nov.The separation of the marine and freshwater specimens was supported by the rbcL,UPA and psbA phylogeny as well as ITS2 se-condary structure inference.Biogeographical reconstruction showed the ancestor of freshwater Hildenbrandia might derive from South America and dispersed from North America to Europe and then to Asian countries,which needs to be verified further with more sam-ples and molecular evidences from South America.

中国淡水胭脂藻属植物形态及分子系统发育分析

以云南省玉溪市和河南省焦作市新采集的2株淡水胭脂藻标本为材料,对其进行形态特征观察和分子系统发育分析,联合我国已报道的其他胭脂藻序列信息,构建该属植物可靠的系统发育关系。根据其现代地理分布模式,对胭脂藻属进行了祖先地理起源重建。基于rbcL、psbA和UPA序列,利用贝叶斯法、最大似然法和邻接法构建的系统发育树高度一致,研究中的标本与鸡公山胭脂藻H.jigongshanensis聚合为一个独立分支,并得到了很高的支持率,根据分子生物学证据,将其鉴定为鸡公山胭脂藻。通过研究中所采集2株鸡公山胭脂藻的形态特征比较,发现传统的形态分类特征包括藻体高度和细胞直径,在不同的环境条件下是可变的,不适合作为胭脂藻属植物种类鉴定的依据。对于胭脂藻属这一形态结构较为简单的类群,必须借助分子生物学证据和系统发育分析手段对其进行种类鉴定和系统发育分析。分子系统发育分析结果表明,中国特有种鸡公山胭脂藻H.jigongshanensis形成单系类群,其与日本胭脂藻H.japananense亲缘关系较近,所有淡水胭脂藻种类形成一个独立的聚类群,与海洋种类遗传差异较大。祖先地理重建的分析结果表明,淡水胭脂藻的祖先起源地位于北美洲,然后逐渐向东加勒比海区域、拉丁美洲和欧亚大陆扩散,形成现代地理分布模式。胭脂藻属独特的种类地理分布特点,可能与其较为古老的起源时间和漫长的进化历史相关,同时淡水胭脂藻在北美洲区域起源时间较早,进化历史漫长,遗传多样性大,这与该地理区域分布的种类H.angolensis为多系类群是相一致的。