鲴亚科分子系统学研究

为探讨鲴亚科(Xenocyprinae)鱼类系统发育关系,研究基于2种线粒体基因和5种核基因序列对鲴亚科各物种的系统发育关系和分化时间进行评估。结果显示:不同方法和数据类型获得了基本一致的拓扑结构。3个属的单系性都得到了很好地支撑;但是,它们之间的进化关系却随着分子标记的不同而改变。这一结果可能是由于早期的基因流或谱系的随机分选所致。此外,银鲴(Xenocypris argentea)、云南鲴(Xenocypris yunnanensis)和黄尾鲴(Xenocypris davidi)之间呈现出嵌套型的谱系关系,暗示它们之间存在基因交流的可能性。基于化石地层年代校正的分子钟估算结果显示,鲴亚科主要类群的分化发生在中新世晚期,约15—12百万年前(Millions of years ago, Ma),这与东亚季风强盛时期的时间相吻合。

MOLECULAR SYSTEMATICS OF XENOCYPRINAE (CYPRINIFORMES,CYPRINIDAE)

Xenocypridinae, as one of the benthic fishes of Cyprinidae (Cypriniformes) in East Asia, contains three genera of about nine species and is one of the smallest subfamilies in Cyprinidae. Despite the small number of species, the phylogenetic relationships of Xenocypridinae still lack a valid and extensive assessment. To this end, this study assessed the phylogenetic relationships and divergence times between members of the subfamily Xenocypridinae using a variety of phylogenetic approaches based on two mitochondrial genes and five nuclear genes. The results showed that analyses based on maximum likelihood and Bayesian approaches harvest consistent topologies, but there are some conflicts in the results based on different datasets. In particular, the monophyly of each of the three genera was well supported in all analyses, but the evolutionary relationships between them were discordant between the results based on mitochondrial and nuclear genes. Analyses based on the coalescent algorithm yielded a third phylogenetic relationship among the genera. These results implied that both ancient gene flow and lineage sorting influenced the relationships between deep clades of the subfamily Xenocypridinae. Additionally, these analyses give insights into the classification of these species, for example, Xenocypris hupeinensis should belong to the genus Xenocypris; the nested relationships among species X. argentea, X. yunnanensis, and X. davidi suggest the possibility of gene flow and the need for taxonomic reconsideration. Finally, a fossil-based molecular clock assessment indicates that the divergence of key Xenocypridinae clades occurred mainly in the late Miocene (ca. 15—12 Ma), which coincides with the intensification of the Asian monsoon and supports the hypothesis that the ichthyofauna of East Asia was established in the early Pliocene and flourished to date. In summary, this study has systematically assessed the phylogeny of Xenocypridinae and made recommendations for future work.