基于线粒体DNA控制区序列的短棘鲾群体遗传学

Population genetics study of Leiognathus equulus based on the control region fragment of mitochondrial DNA

摘要:

物种的遗传结构对推断群体历史动态如有效群体大小、地理分布变迁、基因流、遗传分化等具有重要意义。本实验采用线粒体DNA控制区高变区序列对采自我国海南和台湾的3个短棘鲾群体进行了遗传学比较研究。结果显示，92尾个体共检测到32个单倍型，其中共享单倍型7个；单倍型多样性指数的范围为0.61±0.12~0.86±0.05；核苷酸多样性指数的范围为0.003 3±0.002 4~0.005 3±0.003 4；32个单倍型构建的邻接关系树和最小跨度树均可分为2个单倍型类群，单倍型类群A共有22个单倍型，全部由海南文昌和三亚新村群体构成，单倍型类群B共有10个单倍型，除Hap13外，其余全部由台湾新竹群体构成；台湾新竹群体与海南2个群体之间存在显著差异，但海南文昌群体和三亚新村群体之间无显著差异；中性检验与核苷酸不配对分布分析的结果均显示，短棘鲾2个单倍型类群可能发生了群体扩张事件，扩张时间分别为52 500~105 000和67 600~135 200年前。

关键词:短棘鲾;控制区;遗传多样性;群体遗传结构;隔离

Abstract:

The genetic structure of species plays an important role in inferring population dynamics such as effective population size, geographical distribution, gene flow and population genetic differentiation. In order to reveal the genetic diversity level and genetic structure of Leiognathus equulus populations, a total of 92 individuals from 3 populations were collected and analyzed by control region fragments. The length of the control region fragment was 393 bp. A total of 32 haplotypes were detected for 92 individuals and 7 haplotypes were shared. The haplotype and nucleotide diversity of Xinzhu population was lower than that of two populations from Hainan. The whole haplotype and nucleotide diversity was 0.61±0.12 to 0.86±0.05 and 0.003 3±0.002 4 to 0.005 3±0.003 4, respectively. Two clades (Clade A and Clade B) were obtained in the neighbor-joining tree and median-networks. Clade A consisted of 22 haplotypes, which all were from Hainan populations; Clade B consisted of 10 haplotypes, which all are from Taiwan except Hap13. The haplotype and nucleotide diversity of Clade A was 0.81±0.04 and 0.003 7±0.002 5, and the haplotype and nucleotide diversity of Clade B was 0.69±0.10 and 0.003 3±0.002 4. Significant genetic differentiation was detected between Xinzhu population and the other two populations. The results of AMOVA showed that most genetic variation occurred among groups, which account for 75.37%. Tajima’s D and Fu’s F_s statistics for two clades were significantly negative for these two clades, which rejected the hypothesis of selective neutrality. The mismatch distribution of L. equulus appeared to be unimodal for two clades, and closely matched the expected distributions under the sudden-expansion model. The expanding time may be nearly 52 500-105 000 and 67 600-135 200 years ago in the late Pleistocene for two clades. The present phylogeographic pattern of L. equulus populations may be the combination of historical factors and current factors. The isolation of the Pleistocene glacial land bridge resulted in genetic differentiation of the populations and the isolated population had a secondary connection. Geographical distance hinders gene exchange and promotes the formation of the existing distribution pattern of L. equulus populations.

Key words:Leiognathus equulus;control region;genetic diversity;population genetic structure;isolation