黄东海奇异指纹蛤Acila mirabilis和指纹蛤Acila divaricata群体遗传多样性及进化研究

GENETIC DIVERSITY AND EVOLUTION OF DIFFERENT POPULATIONS OF ACILA MIRABILIS AND ACILA DIVARICATA IN THE YELLOW SEA AND EAST CHINA SEA

指纹蛤属Acila贝类是我国黄东海重要的底栖生物,研究其遗传多样性及进化对了解这一海区环境的变化及与生物的关系具有重要作用。本研究通过线粒体COI基因标记,分析了黄东海常见的两个指纹蛤属物种—奇异指纹蛤Acila mirabilis和指纹蛤Acila divaricata的分化情况,结果表明这两个种的分化形成时间分别在3.71和4.27百万年前,处于上新世时期,我们推测冰期时海平面下降引起的物种栖息地的缩减以及黄海和东海环境条件的不同是导致物种分化的重要原因。通过群体遗传多样性分析,我们发现分布于黄海的4个奇异指纹蛤群体中,3500-10群体的遗传多样性水平最高,且群体遗传多样性自冷水团中心内侧至外侧呈递减趋势,推测这可能与这一群体对冷水团有较好的适应性有关。分布于东海的3个指纹蛤群体均检测到两个单倍型类群ZA和ZB,两类群的分化时间大约在64万年前,发生于更新世中期,我们认为冰期时海平面升降引起的群体地理隔离与二次接触是导致指纹蛤两个单倍型类群形成的主要原因。

Species in Acila genus are important benthic organisms in the Yellow Sea and East China Sea. To study the genetic diversity and evolution within species of Acila genus, and analyze the species differentiation, we analyzed COI gene fragment of two species, A. mirabilis and A. divaricata. The result indicates that the speciation of A. mirabilis and A. divaricata could be dated back to 3.71 and 4.27 million years ago in the Pliocene epoch. Reduction in the species habitat was caused by sea level falling during late Miocene, and the different environmental conditions in the Yellow Sea and East China Sea lead to the differentiation of A. mirabilis and A. divaricata. Analysis in genetic diversity shows that in four populations of A. mirabilis, the genetic diversity of 3500-10 population was the highest, and the genetic diversity from the central to fringe of Cold Water Mass shows a gradually decreasing trend. Therefore, we speculated that this trend may be related to the adaptability to the Cold Water Mass. In three A. divaricata populations, two haplotype taxa were detected, and the differentiation time of these two taxa could be dated back to 0.64 million years ago. We consider that geographical isolation and the secondary contact of different populations caused by sea level fluctuation during glacial period were the main reasons leading to the formation of the two lineages.