中国沿海平疣桑椹石磺COI基因的遗传多样性与遗传分化

Genetic diversity and differentiation of Platevindex mortonifrom the coastal area of China based on mitochondrial COⅠ gene

基于CO I序列,对中国沿海5个平疣桑椹石磺(Platevindex mortoni)群体的遗传多样性及遗传分化进行了分析,84个样本中共检测出单倍型41个,多态性位点117个。总体来说,平疣桑椹石磺具有高的单倍型多样性(0.835±0.039)和核苷酸多样性(0.0572±0.0060)。分子方差分析(AMOVA)表明,65.98%的变异存在于种群间,34.02%的变异发生在种群内。群体间遗传分化固定指数(Fst)、基因流(Nem)及遗传距离分析表明,平疣桑椹石磺已产生了明显的群体间分化。厦门(XM)、湛江(ZJ)和广西(GX)群体间无明显分化,基因流较大(Nem>5),而海南(HN)、苍南(CN)群体分别与其他群体存在显著的分化。单倍型网络图及谱系树同样证实了群体遗传差异的存在。遗传距离模式(IBD)检测显示出,平疣桑椹石磺群体的遗传距离与地理距离之间不存在明显的线性关系。中性检验及历史动态检验推断,ZJ和GX群体可能经历过历史上的瓶颈效应,XM群体经历过历史上的种群扩张,扩张时间推测大约为0.12 Ma BP,可能伴随更新世冰期的气候变暖,海平面上升发生。本研究通过对平疣桑椹石磺mt DNA的CO I基因进行分析,探讨其遗传多样性及遗传分化过程,旨在为该物种种质保护,资源合理开发及生物进化方面研究提供基础资料和理论依据。

The genetic diversity and genetic differentiation of Platevindex mortoni were investigated using mitochon-drial cytochrome c oxidase subunit I （CO I） gene sequences. Groups of nucleotides T, C, A, G contents to an average of 39.54%, 17.56%, 23.07%, 19.83%, showing A ＋ T （62.61%） content is significantly higher than G ＋ C content （37.39%）; mitochondrial genome showed obvious anti G migration characteristics.A total of 84 individuals representing 5 collection sites were included in the analysis. Overall, 41 haplotypes were defined and 117 polymorphic sites were observed. In addition to Hap1 and Hap28 which shared haplotype and 39 haplotypes for each group specific haplotypes, Hap1 is the most widely distributed haplotype, except HN group, distributed in all groups, accounting for 39.3% of all haplotypes. Xiamen group （XM） and Cangnan population （CN） has the most number of haplotypes, which were 12, and HN group haplotypes at least （6）, and 117 polymorphic loci, including 23 single variable sites and 94 parsimony infor-mative sites. Each group of polymorphic loci （Ns） show obvious differences, displayed the span from 10 to 85. The Groups of Zhanjiang （ZJ） and Guangxi （GX） polymorphic loci at least （10）, and the Cangnan group （CN） showed the most polymorphism loci in number, followed by the Hainan group （HN）. Overall, Cangnan population （CN） haplotype diversity （H） and the number of polymorphic loci （Ns） are the group of high level. Each group of haplotype diversity was 0.625～0.889, and the difference was not obvious; the nucleotide diversity was 0.002 0～0.057 2, showing obvious differences. The P. mortoni populations had both high haplotype diversity（0.835±0.039） and nucleotide diversity （0.057 2±0.006 0）. The group number of nucleotide differences （K） also was obviously different, that in groups of XM, ZJ, GX, K was low, only more than 1, while in HN and CN groups, K was high value, which was greater than 30; the entire group also belonged to a higher level, 33.820 7. The AMOVA test of P. mortoni populations based on haplotype frequencies revealed that 34.02% of the genetic variation occurred within the populations, whereas 65.98% of the ge-netic variation occurred among populations. Pairwise fixation index （Fst）, gene flow （Nm） and genetic distance analysis showing significant genetic divergence appeared in P. mortoni populations. HN group and the other four groups showed some genetic distance, and CN group and other groups also showed a large genetic distance. Among small inter groups of ZJ, XM and GX, the genetic distance between ZJ group and GX group had the minimum genetic distance. No obvi-ous genetic differentiations occurred among populations of XM, ZJ and GX （Nem〉5）. While the other group had sig-nificant genetic differentiation, especially in HN group, CN group and other groups generated a high level of genetic differentiation of Fst〉0.25, Nem 0.051 3～0.138 6; gene exchange was very small. The occurrence of a moderate genetic differentiation in CN group and HN group were Fst= 0.149 5 and Nem= 1.422 2. Whereas, the significant genetic diver-gence was found among HN, CN and the other populations, respectively. Haplotype network and phylogenetic tree analyses also indicated genetic divergence occurred among populations. IBD analysis showed no significant correlation between genetic distance and geographical distance. Neutrality test and demographic analyses indicated bottleneck ef-fect might occur in populations ZJ and GX, population expansion in XM population. The time of expansion of XM population could be 0.12 Ma BP. The phenomenon might occur in Pleistocene period with changes of climate warming and rising of sea level. In this study, based on the analysis of flat wart mulberry Onchidium MT DNA of CO I gene, to investigate the genetic diversity and genetic differentiation process, aiming for the species conservation of germplasm, and provides the basic data and theoretical basis of the reasonable development of resources and biological evolution.