中国南部沿海美蓝拟相手蟹的群体遗传多样性研究

Study on Population Genetic Diversity of Parasesarma eumolpe in Southern Coast of China

关键词:  美蓝拟相手蟹  COⅠ基因  遗传多样性  群体历史动态  中国南部沿海

Key words:  Parasesarma eumolpe  COⅠ gene  genetic diversity  population historical dynamics  the southern coast of China

摘要:

为探明中国南部沿海美蓝拟相手蟹（Parasesarma eumolpe）的群体遗传多样性，本文基于线粒体DNA的细胞色素氧化酶亚基Ⅰ（Cytochrome Oxidase Ⅰ，COⅠ）基因片段序列，对中国南部沿海8个美蓝拟相手蟹地理群体共95个个体进行群体遗传多样性分析。结果表明，美蓝拟相手蟹所有个体的线粒体COⅠ基因片段序列长度均为631 bp，共有49个单倍型，群体平均单倍型多样度为0.876 8±0.032 5，平均核苷酸多样度为0.042 2±0.026 3，表现为高水平的遗传多样性。单倍型邻接关系树的拓扑结构显示美蓝拟相手蟹群体没有分化出明显的单倍型类群，尚未形成显著的分支谱系；单倍型的网络关系图呈现出明显的星状结构，未表现出显著的地理谱系结构。分子方差分析（Analysis of Molecular Variance，AMOVA）和群体间的遗传分化指数F_st值结果表明，美蓝拟相手蟹群体在分布范围内尚未形成独立的遗传结构，遗传变异主要来自群体内。核苷酸不配对分布和中性检验结果表明，美蓝拟相手蟹在历史上经历了明显的群体扩张，扩张时间大约在14万年前。幼体阶段具较强的潜在扩散能力，群体间能进行频繁的基因交流，再加上群体扩张事件，可能是美蓝拟相手蟹群体间无显著遗传分化的原因。研究结果有助于揭示我国红树林潮间带相手蟹类种群遗传结构和分子系统地理学规律。

Abstract:

In order to explore the population genetic diversity of Parasesarma eumolpe in the southern coast of China, based on the mitochondrial DNA Cytochrome Oxidase Ⅰ (COⅠ) gene fragment sequence, the genetic diversity of 95 individuals from 8 geographical populations of P.eumolpe in the southern coast of China was analyzed.The results showed that the sequence length of mitochondrial COⅠ gene fragment of all individuals was 631 bp, and there were 49 haplotypes.The average haplotype diversity of the population was 0.876 8±0.032 5, and the average nucleotide diversity was 0.042 2±0.026 3, showing a high level of genetic diversity.The topological structure of haplotype Neighbor-joining (NJ) tree showed that the P.eumolpe population did not differentiate into obvious haplotype groups and did not form a significant branch pedigree.The network diagram of haplotypes showed a clear star-like structure, but did not show a significant geographical pedigree structure.The results of Analysis of Molecular Variance (AMOVA) and F_st value between populations showed that the P.eumolpe population had not yet formed an independent genetic structure within the distribution range, and the genetic variation mainly came from within the population.The results of nucleotide mismatch distribution and neutrality test showed that the P.eumolpe had experienced significant population expansion in history, and the expansion occurred about 140 000 years ago.The larval stage has strong potential dispersal ability, and frequent gene exchange between populations, coupled with population expansion events, may be the reason that there is no significant genetic differentiation between the populations of the P.eumolpe.The results of the study would be helpful to reveal the genetic structure and molecular phylogeography law of the sesarmid crab populations in the intertidal zone of mangroves in China.