基于线粒体DNA标记的阿根廷滑柔鱼2个产卵群体遗传变异分析

Genetic variation analysis of two spawning cohorts of Illex argentinus based on molecular markers of mitochondrial DNA

通过线粒体细胞色素氧化酶Ⅰ(COI)和细胞色素b(Cytb)基因2个分子标记对阿根廷滑柔鱼(Illex argentinus)冬生群体与秋生群体的遗传变异进行了研究,并检验了冬生群体在时间上的遗传差异。结果显示,基于COI基因序列分析得到的单倍型数、单倍型多样性指数、核苷酸多样性指数及平均核苷酸差异数分别为11、0.535±0.066、0.002 24±0.001 59和1.243。基于Cytb基因序列分析得到的单倍型数、单倍型多样性指数、核苷酸多样性指数及平均核苷酸差异数分别为7、0.528±0.058、0.002 65±0.001 89和1.222。2个分子标记均揭示:阿根廷滑柔鱼2个产卵群体具有较高的单倍型多样性指数和较低的核苷酸多样性指数。单倍型邻接树、分子方差分析(AMOVA)及两两群体间的遗传分化系数F st均表明,阿根廷滑柔鱼2个产卵群体间的遗传差异不显著,不存在显著的群体遗传结构。此外,冬生群体在时间上的遗传差异也不显著,。可见,阿根廷滑柔鱼产卵群体间具有频繁的基因流。推测与该物种为大型洄游性种类,生命周期短,以及海洋环流有关。

Illex argentinus is regarded as one of the most important squid species in the southwest Atlantic due to its abundant resources and important ecological status in marine ecosystem. In order to manage and utilize this fishery resource better, it is necessary to investigate its population genetic structure and genetic variance. In this paper, the genetic differentiation between autumn spawning cohort and winter spawning cohort was evaluated and the impact of temporal variation on winter spawning cohort at one location was measured by sequence analysis of mitochondria COI and Cytb genes from L Argentinus . The results showed that the number of haplotype, haplotype diversities, nucleotide diversities and average nucleotide differences were 11, 0.535 ± 0.066, 0.002 24 ± 0. 001 59 and 1. 243 by COI sequences, and 7, 0.528 ± 0. 058, 0.002 65 ± 0. 001 89 and 1. 222 by Cytb sequences, respectively. It was clear that two spawning cohorts of L argentinus were characterized by higher haplotype diversity and lower nucleotide diversity by two genetic markers. A shallow topology of haplotype neighbor-joining （NJ） tree showed no phylogeographic structure between two spawning season cohorts. Analysis of molecular variance （AMOVA） and the pairwise fixation index F-statistics（ Fst ） showed that no significant genetic differentiation existed between two cohorts and the genetic variance mainly came from individuals within populations. In addition, the temporal variation showed significant effect on genetic diversity. In conclusion, the frequent gene flow between two spawning cohorts of L argentinus from the high sea waters of southwest Atlantic was possibly due to its being a migratory species as well as its short life cycles and ocean currents.