怒江濒危鱼类缺须盆唇鱼基于线粒体Cyt b序列的群体遗传结构分析

Population genetic structure analysis of endangered species Placocheilus cryptonemus in the Nujiang River based on Cyt b sequences of mtDNA

测定了怒江缺须盆唇鱼(Placocheilus cryptonemus)5个群体共138尾个体的线粒体DNA Cyt b基因序列,以探讨群体遗传结构和遗传多样性。结果显示:1140bp的Cyt b基因共检测到21个变异位点,从138个样本中得到21个单倍型,平均单倍型多样性(h)为0.826,核苷酸多样性(π)为0.00215,遗传多样性水平较低。5个群体中,泸水群体遗传多样性相对最高,保山道街群体最低。计算5群体的Kimura 2-paramter遗传距离,福贡群体和龙镇桥群体之间的遗传距离最远,为0.00346;泸水群体和保山道街群体之间的遗传距离最近,为0.00093。Fu'Fs中性检验和核苷酸不配对分析暗示了缺须盆唇鱼在历史上可能发生过种群扩张。分子方差分析(AMOVA)表明,5群体间总遗传分化系数Fst=0.3051(P<0.05),群体间具有较高的遗传分化水平。结果说明,怒江缺须盆唇鱼遗传多样性较低,具有较高的遗传分化水平,这可能是由于该物种自身活动能力差以及中游和下游生境明显差异所致。

Placocheilus cryptonemus, a small freshwater fish, which is only endemic to the Nujiang River, mainly inhabits in the middle and lower reaches of the Nujiang River. The stock declined drastically in recent years due to over-fishing, whereas little knowledge is available about its population genetic structure. Here, the mitochondrial DNA （mtDNA） cytochrome b genes of Placocheilus cryptonemus were amplified by means of polymerase chain reaction （PCR） and then sequenced to test the population genetic structure and genetic diversity. Totally 138 individuals were collected from five sites （populations） in Nujiang River, including Gongshan （GS, n=26 ）, Fugong （FG, n=22）, Lushui （LS, n=28）, Daojie （DJ, n=27）, Longzhenqiao （LZ, n=35） .The results showed that 21 variable sites were detected in the aligned sequences of 1 140 bp, and 21 haplotypes were recoverd among the specimens, with only one haplotype shared among all populations. The global haplotype diversity （h） and nucleotide diversity （π） were 0.826 and 0.002 15, respectively.Within populations, LS gained the highest values of genetic diversity, which were 0.804 and 0.00264 for h and π respectively, DJ gained the lowest values of genetic diversity, which were 0.214 and 0.000 32 for h and π respectively. The pairwise Kimura 2-paramter genetic distances between populations were calculated, and the distance between FG and LZ displayed the highest, up to 0.034 6, while that between LS and DJ was the lowest to 0.000 93. The neutral test of Fu＇ Fs showed a significant negative value （-7.664） and the pairwise nucleotide differences distribution showed a singlet, indicating population expansion in history. The fixation indices （Fst） of analysis of molecular variance （AMOVA） among populations was 0.305 1 （P 〈 0.05）, which signaled strong population structure.The data here should be important and useful for making scientific strategy for the natural resource protection of Placocheilus cryptonemus during the development of Nujiang River.Future research should focus on using nuclear and more polymorphic markers such as AFLP or microsatellite DNA to obtain the detail information of the fish.