基于线粒体COⅠ基因序列的东南沿海可口革囊星虫遗传多样性分析

THE GENETIC DIVERSITY OF PHASCOLOSOMA ESCULENTA IN THE COASTAL ZONE OF SOUTH-EASTERN CHINA BASED ON SEQUENCE ANALYSIS OF MITOCHONDRIAL COⅠ GENE

  • 摘要: 为了解我国东南沿海可口革囊星虫自然群体的遗传多样性及遗传结构, 以线粒体COⅠ基因为分子标记, 对浙江象山(XS)与温岭(WL)、福建宁德(ND)、广东湛江(ZJ)4个可口革囊星虫自然群体的80个样本的COⅠ基因片段进行PCR扩增、序列测定和分析。结果表明, 在815 bp长度的核苷酸片段中, A、T、C、G碱基的平均含量分别为29.8%、31.0%、22.6%和16.6%, A+T含量(60.8%)高于C+G含量(49.2%), 表现出较强的AT偏好性。共检测到29个核苷酸变异位点, 定义了29种单倍型, 总群体单倍型多样性指数(Hd)、核甘酸多样性指数(Pi)及平均核苷酸差异数(K)分别为0.932、0.0036及2.8902, 表现出高的Hd和低的Pi。单倍型邻接关系树的拓扑结构简单, 未呈现明显的地理谱系结构。群体内的遗传距离为0.0027—0.0040, 群体间的遗传距离为0.0032—0.0040。两两群体间的遗传分化系数(Fst)和分子方差分析(AMOVA)表明, 可口革囊星虫的遗传变异主要来自于群体内, 而群体间无显著分化。中性检验和核苷酸不配对分布结果揭示, 可口革囊星虫经历了群体历史扩张事件, 大致发生在4.6万年前的更新世晚期。

     

    Abstract: To investigate the genetic diversity and structure of Phascolosoma esculenta wild populations in the coastal zone of South-Eastern China, the mitochondrial cytochrome oxidase subunit Ⅰ (COⅠ) genes as molecular markers were amplified, sequenced and analyzed from 80 organisms sampled in four areas Xiangshan (XS), Wenling (WL), Ningde (ND) and Zhanjiang (ZJ). The results showed that 815 base pair (bp) fragment was consisted of A, T, C and G base with 29.8%, 31.0%, 22.6% and 16.6%, respectively, indicating a greater preference for A and T base because the A+T content (60.8%) was higher than that of G+C (39.2%). Besides, twenty-nine polymorphic sites and haplotypes were identified in all the sequences. Total haplotype diversity (Hd), nucleotide diversity (Pi) and the average number of nucleotide differences (K) were 0.932, 0.0036 and 2.8902, respectively. A shallow topology of haplotype neighbor-joining (NJ) tree with simple topological structure showed no phylogeographic structure among four populations. Genetic distance within and between P. esulenta populations were 0.0027—0.0040 and 0.0032—0.0040, respectively. Genetic fixation index (Fst) and analysis of molecular variance (AMOVA) indicated that the genetic variance mainly came from individuals within populations, and no genetic differentiation was among populations. Neutral test and mismatch-distribution analysis revealed that the populations of P. esculenta had ever experienced population expansion that occurred in about 0.046 million years ago in the late pleistocene epoch.

     

/

返回文章
返回