甘肃省鱼类资源现状及DNA条形码在鱼类物种鉴定中的应用

为了摸清甘肃省土著鱼类资源与分布现状, 探索DNA条形码在鱼类辅助物种鉴定中的适用性, 2012年6-9月对甘肃境内黄河水系、嘉陵江水系和河西内陆河水系进行了较全面的鱼类调查。共采集鱼类标本3,087尾, 隶属于5目10科38属64种, 以鲤科种类最多, 为30种, 占总种数的46.88%。物种多样性分析表明, 在黄河水系的夏河和庄浪河多样性指数是所有调查点中最低的, 分别为1.38和1.09。嘉陵江水系各河段的多样性指数较高(H = 2.15-3.27), 其次为河西内陆河水系(H = 2.01-2.83)。在河西内陆河水系中, 疏勒河的均匀度指数最高, 为1.10, 黑河最低(0.68)。庄浪河的优势度指数最高, 为0.34, 而嘉陵江干流两当段的优势度指数在所有调查点中最低, 为0.04。利用DNA条形码分析了49种662尾标本的COI基因部分序列, 大部分种类在neighbor-joining系统树中形成各自的单系, 种内平均遗传距离0.88%, 种间平均遗传距离为9.99%, 在种内和种间COI序列遗传距离之间形成明显的条形码间隙, 斯氏高原鳅(Triplophysa stoliczkae)与达里湖高原鳅(T. dalaica), 甘肃高原鳅(T. robusta)与似鲇高原鳅(T. siluroides), 嘉陵裸裂尻鱼(Schizopygopsis kialingensis)与黄河裸裂尻鱼(S. pylzovi)之间的遗传距离低于2%, 甘肃高原鳅与似鲇高原鳅不能通过COI基因片段区分开, 其他两对物种可以采用核苷酸诊断法来进一步区分。斯氏高原鳅和拉氏鱼岁(Phoxinus lagowskii)种内遗传分歧较大, 揭示种内可能存在隐存种。结果表明, 对某些近缘种和不同地理种群差异较大的物种, 要将分子、形态和地理分布特点结合起来才能准确鉴定。

Current freshwater fish resources and the application of DNA barcoding in species identification in Gansu Province

Between June and September in 2012, we investigated fish resources from the Yellow River, Jialing rivers and Hexi inland rivers in Gansu Province, China. Three thousand specimens were collected, belonging to 64 species, 38 genera, 10 families and 5 orders. Cyprinidae was the predominant species, accounting for 45% of the total species. Diversity analysis showed that fish diversity in the Jialing River basin was the highest (H = 2.15-3.27), followed by the inland rivers (H = 2.01-2.83). Two tributaries of the Yellow River, the Xiahe River and the Zhuanglang River had relatively lower diversity levels with the H values of 1.38 and 1.09, respectively. The Pielou index of Shule River was the highest with a value of 1.10, while that of the Heihe River was the lowest with a value of 0.68. The Simpson index of the Zhuanglang River was 0.34, the highest of the investigated rivers, while the trunk streams of Jialing River was the lowest. A total of 662 specimens of 49 species were randomly selected for DNA barcoding analysis using a partial sequence of the COI gene. The results indicated that most species formed monophyletic groups in the neighbor-joining tree. The average K2P genetic divergence was 0.88% within species and 9.99% among species. A significant barcode gap was found between intraspecific genetic distance and interspecific genetic distance. A nucleotide diagnostic method was needed for further identification because the K2P genetic distance of three species pairs (between Triplophysa stoliczkae and T. dalaica, T. robusta and T. siluroides, Schizopygopsis kialingensis and S. pylzovi) was less than 2%. Cryptic species may exist within Triplophysa stoliczkae and Phoxinus lagowskii. Triplophysa robusta and T. siluroides cannot be distinguished through COI gene sequences. The results showed that molecular methods, morphological characteristic and geographical distribution of species should be combined in order to comprehensively and accurately identify closely related species and geographic populations.