青海省6种裂腹鱼COI基因作为DNA条形码的适用性初探

青海省裂腹鱼鱼类至少有20种,占土著鱼类的40%以上,具有重要的生态价值。由于生态环境的恶化和人为因素的干扰,很多物种群已濒临灭绝。快速和准确的物种鉴定对于这些物种的保护至关重要,而基于形态学的传统分类法很难满足这一需求。因此,本研究通过DNA条形码技术初步探讨了在青海省裂腹鱼物种鉴定中的适用性。本研究中,测序获得了青海26尾裂腹鱼(6个物种)的细胞色素c氧化酶亚基I (COI)基因,并经GenBank数据库进行比对;基于K2P模型分析COI序列变异;运用贝叶斯法(BI)和最大似然法(ML)构建系统发育树。结果显示,6种裂腹鱼COI序列检测得到15个单倍型,且各物种间无共享的单倍型。基于K2P模型,最大种内遗传距离和最小种间遗传距离分别为(0.621±0.297)%和(2.792±0.644)%。种间平均遗传距离为(12.205±1.307)%,约为种内平均遗传距离((0.327±0.162)%)的37倍,表明各物种的COI序列间已经形成明显"条形码间隙"。AMOVA分析显示,遗传变异主要来自种间,约占97.05%;FST=0.970 54,p<0.01,说明各物种间分化程度极高。此外,基于BI和ML方法构建的系统树具有一致的拓扑结构,分辨率较高;各物种均单独聚为一个发育枝,拓扑结构合理。以上结果表明,COI基因作为DNA条形码在青海裂腹鱼物种鉴定中具有较高的适用性。

Preliminary Study on the Applicability of COI Gene as DNA Barcode in Six Species of Schizothoracine Fishes in Qinghai Province

There are at least 20 species of Schizothoracinae fish being distributed in Qinghai province, accounting for more than 40% of the native species, which play an important role in ecosystem. Due to the deterioration of the ecological environment and the interference of human activities, many species are on the verge of extinction.Therefore, rapid accurate species identification is essential for the protection of these species. Traditional classification based on morphology, however, is difficult to meet this demand. Herein, the applicability of DNA barcode technology in the identification of the Schzothoracinae species in Qinghai province was preliminarily discussed in this paper to provide an effective tool for resource assessment. Partial sequences of the cytochrome c oxidase subunit I(COI) gene of 26 specimens(6 species) were acquired via sequencing, and then determined and verified by comparison with the GenBank database. Genetic variation of COI sequences from Schizothoracine fishes were analyzed based on Kimura-2-parameter model;Phylogenetic trees were constructed using Bayesian inference(BI) and Maximum Likelihood(ML) methods. The results showed that 15 haplotypes were detected from6 species, and no shared haplotype was found among these species. Based on K2P model, the maximum intraspecific K2P genetic distance and the minimum interspecies K2P genetic distance were(0.621±0.297)% and(2.792±0.644)%,respectively. And the inter-species average genetic distance calculated by K2P model was(12.205±1.307)%, which was about 37 times of the intra-species average genetic distance((0.327±0.162)%), suggesting that there was a significant "barcode gap" among the COI sequences of each species. AMOVA analysis showed that the source of genetic variation was mainly from interspecies, accounting for 97.05%;FST=0.970 54, p<0.01, implying that the degree of differentiation among species was extremely high. In addition, the phylogenetic trees constructed by the two methods had a consistent topology structure with high resolution, 6 species were each clustered together with reasonable topologies. Above all, the COI gene as DNA barcodes showed high applicability in species identification for schizothoracine fishes in Qinghai province.