伊洛河马口鱼遗传差异及其种群分化研究

GENETIC DIVERGENCE AND POPULATION DIFFERENTIATION ANALYSIS OF OPSARIICHTHYS BIDENS FROM YILUO HE

  • 摘要: 研究利用细胞色素b(Cyt b)基因分析了采自于伊洛河的48个马口鱼(Opsariichthys bidens)个体间的遗传距离, 并构建其系统发育关系。分析结果显示, 48个个体聚为两个支持率为100%的分支, 分支间没有共享单倍型。每个分支的样本覆盖了所有的采样点, 分支内个体间的平均遗传距离为0.2%, 而分支间的遗传距离为3.1%。微卫星分析结果显示, 99.88%的遗传差异来自于种群内个体间, 种群间的差异只占了0.12%, 两个分支种群并没有发生显著的遗传分化(Fst=0.0012, P=1)。以δ13C和δ15N构建了两个分支的生态位, 结果显示, 伊洛河马口鱼的两个分支的营养生态位没有发生分离。基于线粒体Cyt b基因的遗传分歧, 伊洛河马口鱼的两个分支可能代表不同的物种。但它们在种群遗传结构上并没有发生显著的种群分化, 个体间亲缘关系树与系统发育树的分歧暗示种群间不存在生殖隔离, 营养生态位也没有分离。研究结果并不符合隐存种的解释, 伊洛河马口鱼两个分支间线粒体DNA的遗传差异可能源自于祖先种群或者种间杂交。

     

    Abstract: Often deep genetic divergence indicates potentially different species. However, exceptions are occasionally found. In this study, samples of Opsariichthys bidens from a tributary of the Yellow River (Yiluo River) were analyzed using the mitochondrial cytochrome b (Cyt b) gene, simple sequence repeats (SSR), and the method of stable isotope was used to explore their species status. Phylogenetic trees were reconstructed with the neighbor joining (NJ) and Bayesian inference (BI) methods based on the Cyt b gene sequences and two well supported clades were recovered. Shared haplotype was not detected between these two clades and the average genetic divergence of 3.1% between them seemed to reach the criterion of DNA barcoding for species identification. Nevertheless, analyses of SSR revealed no significant genetic differentiation between the clades (Fst=0.0012, P=1), with 99.88% of variation occurring among individuals. Besides, isotope composition of δ13C and δ15N demonstrated that the two clades shared a common diet with no nutrient niche separation between them. Analysis of SSR and stable isotopes indicated that the two mitochondrially well-separated clades of O. bidens could not be explained by cryptic species, although their deep genetic distances of the Cyt b gene was derived from their ancestral populations.

     

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