乔氏新银鱼基于细胞色素b序列的种群遗传结构和种群历史

为促进乔氏新银鱼(Neosalanx jordani)种质资源的保护, 采集了长江流域和淮河流域5个乔氏新银鱼地理种群计129个样本, 利用线粒体细胞色素b基因(Cyt b)全序列作为分子标记, 初步分析了乔氏新银鱼种群的遗传多样性、遗传结构及种群历史动态。研究结果共检测到18个Cyt b单倍型, 发现和其他鱼类相比, 乔氏新银鱼具有较高的单倍型多样性(h, 0.590±0.047), 但核苷酸多样性较低(π, 0.00088±0.00011)。分子变异分析(AMOVA)表明, 乔氏新银鱼5个地理种群内个体间和流域内种群间均存在显著的遗传差异, 而长江流域与淮河流域之间遗传分化不明显, 显示乔氏新银鱼遗传分化与当前水系的分布格局不吻合。结果表明乔氏新银鱼目前的遗传格局主要是由于长距离独立的建群事件、基因流限制以及种群的持续扩张的共同作用而形成的。种群历史动态分析结果显示乔氏新银鱼种群为近期扩张种群, 其大部分变异发生在1.897万年之内, 与最后一次冰期全面消退、海平面上升、长江流域及淮河流域中下游大量湖泊(适宜生境)形成的时间相吻合。建议对现存的乔氏新银鱼种群, 特别是遗传多样性较高的那些种群(如鄱阳湖、太湖及洪泽湖种群)分别保护。

Population genetic structure and demographic history of Neosalanx jordani based on cytochrome b sequences

To assess the genetic diversity, population structure and demographic history of Neosalanx jordani, we sequenced complete mitochondrial DNA (1,141 bp) from the cytochrome b (cyt b) gene for 129 individuals from five populations in the Yangtze River and the Huaihe River basins. We identified18 haplotypes, and haplotype diversity was high (h=0.590±0.047). Nucleotide diversity was relatively low (π = 0.00088±0.00011) among all haplotypes. Phylogenetic analysis failed to detect significant geographic structure. Analysis of molecular variance (AMOVA) revealed significant genetic subdivision among individuals within populations and among populations within basins but not between basins, indicating distribution of genetic diversity was inconsistent with contemporary hydrological structure. We suggest that the present complex genetic pattern ofN. jordani resulted from multiple unrelated founding dispersal events (long-distance colonization), contiguous population expansion, and restricted gene flow. Demographic analysis revealed that this species may have experienced a relatively recent population expansion, and the majority of mutations occurred 18.97 kyr ago. This timing is consistent with the estimated time of sea level rise and the formation of large-scale appropriate habitats during the last glacial maximum (LGM). Thus, we suggest that all populations, especially those with high genetic diversity, should be separately managed and conserved.