基于线粒体Cyt b基因序列的绿鳍马面鲀6个野生群体的遗传结构分析

利用线粒体细胞色素b(cytochrome b,Cyt b)基因分析了我国沿海绿鳍马面鲀(Thamnaconus septentrionalis)6个野生群体(大连、秦皇岛、蓬莱、日照、舟山和汕头)的遗传多样性和群体遗传结构。结果显示,在176个个体915 bp的Cyt b部分序列中共检测到32个变异位点和30个单倍型;6个群体的单倍型多样性为0.883~0.953,核苷酸多样性0.0032~0.0039;群体间固定指数较小,呈中低度分化;AMOVA分析表明,遗传变异主要来源于群体内,群体间遗传分化未达到显著水平。群体历史动态分析表明,绿鳍马面鲀在16.9万~42.2万年前经历种群扩张。总体上,各群体间的遗传分化较小,并未形成相应的地理支系,推测黑潮的输送作用以及绿鳍马面鲀的洄游习性维持了各群体间高强度的基因交流;中更新世中晚期的气候波动对绿鳍马面鲀的种群扩张以及地理分布格局可能具有重要影响。本研究结果加深了人们对于绿鳍马面鲀资源情况的认识,为绿鳍马面鲀资源的保护和合理利用提供了理论依据。

Population genetic structure of Thamnaconus septentrionalis in China's coastal waters based on mitochondrial Cyt b sequences

Genetic data have aided fishery conservation research and management by facilitating the detection of genetically distinct populations, the measurement of genetic connectivity, and the identification of the risks associated with demographic change and inbreeding. Thamnaconus septentrionalis is an important economic marine fish species in China and inhabits in the Bohai Sea, Yellow Sea, East China Sea and South China Sea. T. septentrionalis has become an important fishing target in the East China Sea since 1974. Its annual catches were once second only to Trichiurus lepturusA1]. However, the resource of T. septentrionalis has declined sharply since 1990 due to overfishing and ocean environmental change. To provide better protection and effective recovery for this species, it is urgent to evaluate its population structure and genetic diversity. However, population surveys of T. septentrionalis in China''s coastal waters were rare. No population structure research based on molecular makers was available. In this study, we amplified the partial mitochondrial Cyt b gene sequences of 176 individuals from six populations (Dalian, Qinhuangdao, Penglai, Rizhao, Zhoushan, and Shantou). The results showed that 32 polymorphic nucleotide sites and 30 haplotypes were detected among all the Cyt b sequences. The haplotype diversity ranged from 0.883 to 0.953, and the nucleotide diversity was 0.0032-0.0039. This genetic diversity pattern was probably caused by a recent demographic expansion in the Pleistocene, a rapid population growth after 1970, and the adaptable biological characteristics of T. septentrionalis. Although the haplotype diversity was high, the genetic diversity is still vulnerable to overfishing. AMOVA analysis showed that the genetic differentiation of T. septentrionalis mainly occurred within the population variation. The genetic differentiations among populations were weak and no groups were identified. The high gene exchange among populations is probably caused by the seasonal migration behaviors of the adults and the long-distance transportation of juveniles by the Kuroshio (Black) Current. Demographic history analysis showed that the six populations experienced rapid population growth 0.17-0.42 Mya. This time point was within the middle Pleistocene. During this period, sea levels changed dramatically due to unstable temperatures. We speculate that the sea level changes during the middle Pleistocene might have had significant influence on the population expansion of T. septentrionalis. To our knowledge, this is the first population genetics research on T. septentrionalis in China''s coastal waters based on molecular markers. This study could deepen our understanding of how to optimize the utilization of the natural resources of T. septentrionalis.