Speciation In The Chinese Endemic Genus Dipelta

Speciation is a vital proposition in the study of evolutionary biology and biodiversity.The formation of biodiversity mechanism in western China has aroused researchers' extensive attention for a long time.In this study,we collected populations of Chinese endemic genus Dipelta in its natural region to investigate the phylogenetic relationship among Dipelta species and the process of speciation between Dipelta yunnanensis and D.floribunda based on genetic data from three cpDNA fragements and five nuclear DNA fragments and ecological niche modelling analysis.30 haplotypes were identified from overall 547 individuals in D.floribunda and D.yunnanensis based on concatenated three cpDNA fragments,and two haplotypes were shared between two species.There was only one haplotype identified in D.elegans.Further,we reconstructed the phylogenetic relationship of Dipelta,illuminating three taxa of Dipelta,namely,D.floribunda,D.yunnanensis and D.elegans.In addition,the phylogenetic reconstruction of haplotypes also shown that D.yunnanensis and D.floribunda are sister groups,and D.elegans were basal taxa of Dipelta species.The results based on five nuclear loci indicated that most nuclear haplotypes were exclusive in D.floribunda or D.yunnanensis,consistent with the distinct population structure and high level of genetic differentiation between species.The best-fit model supported by the approximate Bayesian computation(ABC)analysis indicated that D.floribunda and D.yunnanensis diverged during the mid-Pleistocene period,consistent with the largest glacial period in the Qinghai-Tibet Plateau(QTP).Meanwhile,the historically inter-specific gene flow was tested.The results indicated that interspecific divergence of D.floribunda and D.yunnanensis has much to do with Quaternary climate oscillation.The process of divergence between two species experience long-term gene flow.What's more,there exist the asynchronous responses of related species to the contemporary climate changes owing to the isolation of Sichuan Basin.Consequently,our results suggested that complex topography should be considered in understanding the distributional patterns even for closely related species and their demographic responses.To sum up,identifying the taxonomic status of Dipelta species again and reconstructing the phylogenetic relationship of Dipelta species provided reference for the work of biodiversity protection.In addition,the study about formation of allopatric pattern between D.floribunda and D.yunnanensis will provide paradigm for some researches about those species having the same or similar distribution.