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Diversification and vicariance in two species complexes of Tomocerus (Collembola) from China
2014-05-22 | 【print】【close

The Qinling-Dabie Mountains-Huai River line/zone has been traditionally regarded as the geographical, climatic, agricultural and demographic boundary between north and south regions in eastern China. Human activities are frequently in eastern China, where the topographical differences are relatively small particularly in eastern plain region. The north-south boundary were considered to have weaker impacts on geographical patterns of fauna than Himalayan Mountains and Qinghai-Tibet Plateau in western China. Many animals including birds, mammals, insects etc., have broad distributions, spanning both southern and northern areas in eastern China. In these cases, Qinling-Dabie Mountains-Huai River line/zone seems to play a limited role in driving vicariant speciation in widespread species. However, the wide distribution of Collembola was doubted because of low long distance dispersal capability.

Dr. Zhang, one of the previous postdoc in Prof. Chao-Dong ZHU’s research group (zhucd@ioz.ac.cn) at the Institute of Zoology, Chinese Academy of Sciences, has quite good background on taxonomy and data collection on Collembola in both Nanjing University and Nanjing Agricultural University. Collaborating with researchers from different institutions, he studied the vicariance of springtails resulted by north-south geographical line/zone. Two species, Tomocerus ocreatus and T. nigrus, are widespread in eastern China. They are found to be isolated by the Qinling Mountains-Huai River line.

The team recognized 22 DNA-based species based on COI, 16S rRNA and 28S rRNA fragments by using a general mixed Yule coalescent model and a Bayesian multilocus approach. Multiple-locus species delimitation supports the presence of extensive cryptic diversity in both species that are geographically widespread. In addition to genetic differences, we discovered corresponding morphological differences in jumping organs among the major clades. This finding indicates possible the jumping cability might lead to speciation.

Analyses of divergence times and historical biogeographical processes revealed that T. ocreatus and nigrus complexes originated in southern and northern China, respectively. We estimated their divergence time at 27.8–44.9 Mya during the Eocene–Oligocene, at the time when the Qinling-Dabie Mountains uplifted and formed the north–south geographical boundary in eastern China. Diversification analyses support the constant-rate in speciation, and suggest that the subsequent orogenesis of the Qinghai-Tibetan Plateau in western China had little impact on divergences within the two species complexes. Both species complexes maintain their geographical patterns from the Paleogene to the present day.

Our findings point to a potentially important influence of Qinling-Dabie Mountains-Huai River line/zone on both animal speciation and geographical distribution patterns in eastern China. The study has been published online in Zoologica Scripta (http://onlinelibrary.wiley.com/doi/10.1111/zsc.12056/abstract ).

This project was supported mainly by the National Science Foundation, China (Grant No. 31101622, J1210002) and partially by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KSXC2-EW-B-02).

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