基于线粒体COⅠ序列的中国前鳞鮻 遗传多样性分析

Genetic Diversity of Liza affinis in Coastal Waters of China Deduced from Mitochondrial COⅠSequences

关键词:  前鳞鮻  遗传多样性  COⅠ基因  中国沿海

Key words:  Liza affinis  Genetic diversity  Cytochrome oxidase subunit I gene  Coastal waters of China

摘要:

前鳞鮻(Liza affinis)是分布于西北太平洋的日本南部及中国台湾海域等的经济鱼类。为了解中国前鳞鮻的遗传背景，该研究分析了采自中国4省82尾样本COⅠ基因5端712 bp序列，共发现21个单倍型，遗传多样性(Hd=0.4840±0.0700, π=0.0010±0.0002)较低。根据群体所属的地区、海域、海峡进行分组，通过AMOVA分析，得出组间的Fst值皆小于0.05，P值皆大于0.05，组间变异的比例极低(–0.6%~0.46%)，表明中国前鳞鮻群体间无明显分化，其原因可能是：1)频繁的基因交流。前鳞鮻的洄游范围较大，且受海流影响，导致不同地区的群体间有着密切的基因交流；2)近期种群扩张事件。中国前鳞鮻整体的Fu’s Fs值为显著性负值(FS= –20.3900，P=0)，核苷酸错配峰图为明显单峰，单倍型网络图呈星状结构，均表明中国前鳞鮻群体经历过种群扩张，估算扩张大约发生在13.4199~1.4911万年前，可能是冰期和间冰期的交替中海平面的变化所致。此外，洞头群体的遗传多样性(Hd=0.8080±0.1130，π=0.0021±0.0006)明显高于其他地理群体，建议将其作为优先保护的对象。

Abstract:

To assess the genetic background of Liza affinis in the coastal waters of China, the sequence variation in 712 bp of the partial mitochondrial DNA COⅠgene of 84 individuals from 4 provinces was analyzed. In total, 18 polymorphic sites defined 21 haplotypes and low levels of genetic diversity (Hd = 0.8230±0.0400, π=0.0023±0.0002) were detected. Individuals from different sites were intertwined together in the parsimony network, suggesting no geographical clustering. AMOVA analysis of various groupings (sampling sites, seas, division of the Taiwan Strait and Qiongzhou Strait) detected no significant genetic differentiation, as evidenced by pairwise fixation indexes (Fst = –0.1940 ~ 0.0141, P > 0.05), and the percentage of variation (–0.6%~0.46%) among groups. In the SAMOVA analysis, the Dongtou population was treated as one group, and the others were treated as another group; the percentage of variation among groups was 2.87%, congruent with the results of Fst and AMOVA analysis. The pattern of no lineage structure and no obvious genetic differentiation in L. affinis populations in coastal waters of China might have been caused by: 1) Passive transport of larvae and juveniles by marine currents, or active feeding migration and spawning aggregation of adults. 2) Recent population expansion. Significant negative Fu’s Fs for all populations (FS = –20.3900, P = 0), and obvious unimodal nucleotide mismatch distribution suggested that L. affinis in coastal waters of China had experienced population expansion and the deduced expansion time was approximately 134.199~14.911 kaBP; i.e., in the late Pleistocene, which might have been caused by the rise and fall of sea-levels with dramatic climatic changes during glacial-interglacial cycles. The Dongtou population should be given priority protection as it has the highest genetic diversity (Hd = 0.8080±0.1130, π = 0.0021±0.0006) among the populations that were studied. Because the study only involved limited L. affinis populations in China, COⅠ might be a more conservative molecular marker than evolutionarily faster control region. Furthermore, maternally inherited mtDNA is independent of nuclear inheritance, and may not completely represent the evolutionary history of a species. Thus, future studies should incorporate more sampling sites across the species range using both nuclear and mtDNA markers together. A better understanding of the genetic background of L. affinis will provide a sound scientific basis for the preservation and sustainable utilization of its germplasm resources.