赤水河两种荷马条鳅属鱼类的遗传多样性及谱系生物地理学过程分析

研究以线粒体Cyt b基因为分子标记，对赤水河两种荷马条鳅属（Homatula）鱼类（红尾荷马条鳅和短体荷马条鳅）的遗传多样性及种群结构进行了分析；同时，结合了对在长江上游其他几个水系分布的同种鱼类进行比较，分析其生物地理学过程。遗传多样性分析结果表明，5个水系135尾红尾荷马条鳅Cyt b基因序列共检测出42个单倍型，单倍型多样性和核苷酸多样性分别为0.936和0.00493；其中，赤水河种群的分别为0.891和0.00208。3个水系52尾短体荷马条鳅Cyt b基因序列共检测出12个单倍型，单倍型多样性和核苷酸多样性分别0.821和0.01105；赤水河种群的分别为0.646和0.00390。基于ML和BI法构建的单倍型分子系统发育树结果表明，两物种各自构成单系，且得到较强支持。红尾荷马条鳅各种群地理格局分布明显，赤水河种群为并系类群位于分支基部。在短体荷马条鳅支系中，岷江与沱江两个水系的个体相互聚类在一起，而赤水河群体聚成一个分支。赤水河与其他水系不存在共享单倍型，表现了明显的隔离和差异性的地理分布格局。由于这些水系之间地理位置相距较远，推测这种格局的形成不是地质运动造成的水系隔离，而是历史时期水位的高低变化造成鱼类种群的扩散和隔离。错配分析支持赤水河两物种种群扩张的推断，但中性检验却并非全部支持，显示种群历史相对复杂。

GENETIC DIVERSITY AND PHYLOGEOGRAPHY OF TWO HOMATULA SPECIES (TELEOSTEI: NEMACHEILIDAE) IN THE CHISHUI RIVER

The Chishui River, the important part of the Rare and Endemic Fishes Nature Reserve in the upper Yangtze River basin, plays an irreplaceable role in biodiversity conservation. The present study used mitochondrial DNA (mtDNA) Cyt b gene as molecular maker to perform the genetic diversity and phylogeographic analyses of two species of Homatula (H. variegata and H. potanini) from the Chishui River and nearby rivers. 42 haplotypes were identified for 135 individuals of H. variegata from 5 rivers, and 12 haplotypes for 52 individuals of H. potanini from 3 rivers. Rela-tively high haplotype diversity were detected (hH. variegata=0.936, hH. potanini=0.821) with low nucleotide diversity in H. variegates (π=0.00493) and high nucleotide diversity in H. potanini (π=0.01105). Haplotype diversity and nucleotide diversity of H. variegates in the Chishui River were 0.891 and 0.00208, respectively, and their values were 0.64 and 0.00390 for H. potanini from the same river. Phylogenetic analyses for all haplotypes based on ML and BI methods re-vealed that H. variegata and H. potanini were separately clustered as their own monophy. The phylogeny of H. varie-gates clad showed the population from the Chishui River as paraphy located at the basal position of this clad, and all samples were separately clustered together according to their drainages with an obvious pattern of geographic distribu-tion, while this pattern was not observed in samples of H. potanini. No haplotypes from the Chishui River were shared with other rivers, showing a significant isolation and difference in geographic distribution patterns. Because of the far distance between these rivers, it is speculated that the formation of this pattern was not caused by geological movement, but maybe resulted from the fluctuation of water level in the ancient time. Mismatch distribution analysis indicted the recent demographic expansions of Homatula populations in the Chishui River, but not all neutrality tests supported this hypothesis. These results suggest the relatively complex demographic history of Homatula species in the Chishui River.