Speciation and phylogeny of the lancelet, Branchiostoma belcheri (Gray) in East Asian waters, as viewed from molecular and morphological analyses

1.对日本文昌鱼3个地方种群（恩州那达湾、濑户内海和阿马库萨）的等位酶分析表明，在9个多态性位点中，有5个位点在种群间存在显著差异。但Fst的总体值较小（0.007），说明群体间应该存在一定程度的遗传交流.基于线粒体细胞色素C氧化酶亚基I（C 01）和16 S核糖体RNA核苷酸序列的分子系统学研究对青岛阿马库萨、濑户内海、五所湾、恩州那达湾的贝氏B.belcheri进行了16 SrRNA基因分析（华北），以及厦门附近的吉门岛（华南）;来自泰国湾和普吉岛的B.malayanum;来自日本冲绳的Epigonichthys lucayanus（作为外群）; E.maldivense（do.）台湾;结果表明：（1）B. belcheri各地方居群间无显著性差异;这是出乎意料的，因为青岛加上日本和厦门人群之间已经认识到显着的形态差异。(2)在基于C 01和16 S rRNA基因遗传距离的邻接树中，太平洋种（B.belcheri和B.malayanum）和大西洋种（B.lanceolatum和B.floridae）被聚为一个独立的类群，后者的分支长度远短于太平洋种。(3)根据C 01基因的序列数据，测定了大西洋种与太平洋种之间的分歧时间约为2.5年。1.1亿年前，Branchiostoma和Epigonichthys物种约。一亿三千万年。相反，B.lanceolatum和B.floridae之间的分歧时间估计为零。

1. Allozyme analysis for the 3 Japanese local (Enshu-nada Sound, Seto Inland Sea, and Amakusa) populations of Branchiostoma belcheri, revealed statistically significant differences among them at 5 out of 9 polymorphic loci. However, the smallness of the overall value of Fst (0.007) indicates that there should be a certain degree of genetic exchanges among the populations.2. Molecular phylogenetic studies based on nucleotide sequences of mitochondrial cytochrome C oxidase subunit I (C01) and 16S ribosomal RNA (16S rRNA) genes were performed for B.belcheri from Enshu-nada Sound, Gokasho Bay, Seto Inland Sea, Amakusa, Qingdao (North China), and Jimmnen Island, near Xiamen (South China) ; B.malayanum from Gulf of Thailand and Phuket ; Epigonichthys lucayanus (as an outgroup) from Okinawa, Japan ; E.maldivense (do.) from Taiwan ; and Atlantic B.floridae and B.lanceolatum, both cited from DDBJ.The results are :(1) No significant differences were detected among all the analysed local populations of B.belcheri. It is unexpected because marked morphological differences have been recognized between Qingdao plus Japanese and Xiamen populations.(2) In the neighbor-Joining trees among the six species based on the genetic distances in the C01 and 16S rRNA genes, the Pacific pairs (B.belcheri and B.malayanum) and the Atlantic ones (B.lanceolatum and B.floridae) were clustered each into a distinct group, with the branch lengths of the latter from the node of the cluster being much shorter than those of the Pacific.(3) On the basis of the sequence data of C01 gene, the divergence time between the Atlantic and Pacific species about was measured ca. 110 million years ago and that the Branchiostoma and Epigonichthys species ca. 130 million years. In contrast, the divergence time between B.lanceolatum and B.floridae was estimated zero.