Molecular Geographical Study Of The Endemic Species Of Chinese Creek In The Yangtze River (Fusiforme)

Quaternary climatic oscillations have played a significant role in shaping the present geographical distribution and genetic structure of temperate species. To further understanding the effect on the genetic differentiation and population genetic structure of eastern species of China due to the Quaternary ice ages and rise of the Qinghai-Tibetan Plateau (QTP), a ture freshwater crab Sinopotamon yangtsekiense Bott,1967 was chosed as a representative mainly distributed drainages in east China to study the historical processes that may be responsible to the contemporary geographic distributions. The wide range distribution and low dispersal capabilities of this species make it as a good model for the investigation of palaeoclimatic influence on the phylogeographic pattern.In the present study, a total of twenty microsatellite loci were isolated from S. yangtsekiense using the FIASCO protocol for the next population genetic analysis. The combined maternally inherited mtDNA, biparentally inherited microsatellite DNA, and the both potential Current and LGM distribution under the framework of the climate model were used to analyze the phylogeographic patterns of S. yangtsekiense. A total of 482 individuals were sampled across the Yellow River, Huaihe River, and Yangtze River spanning the distribution range of this species. Two mitochondrial fragments(coxl and nad5, together about 1206 bp in length) of 243 individuals were sequenced. All adult 482 individuals were examined from 34 sites using eight microsatellite loci. The major conclusions are as follows:(1) The genetic structure of S. yangtsekiense exists two distinct clusters (A and B):A clade comprises of the Yellow River (YR) and headstream of Huaihe River (HHR); and the clade B includes the Huaihe River and Yangtze River populations. Based on the molecular clock estimate, the divergence time between two clusters is about the 2.6 Ma. It might be explained by the rise of Qinling Mountain and the difference between the south and north climatic changes resulting from the uplifted QTP.(2) The cold and dry climate played prominent roles in the growth and reproduction of S. yangtsekiense during the LGM, leading to the decline of the effective population size of S. yangtsekiense. Presumably, some low mountains or hilly areas are still suitable environment for the survival of this species in the Headstream of Huaihe River (HHR), Upper of Huaihe River (UHR), Middle of Huaihe River (MHR) and Huang Mountain regions (HMR), implying that these regions were potential refugia in situ or nearby areas for S. yangtsekiense.(3) With the rise of the QTP and Mts. Qinling, the differentiation of north and south climate become more and more obvious in China. Moreover, the variations of the curved terminal segment of first pleopod of the male for the three subspecies might be related to the adaptation to local gradual climate types changes from the east (more humid), middle (dry) to northwest (more dry) China.(4) A redelimitation of S. y. tongbaiense subspecies on the basis of the mt and SSR markers demonstrated that the S. yangtsekiense distributed in the headstream of Huaihe River is the typical S. y. tongbaiense; and the S. yangtsekiense (previously recognized as S. y. tongbaiense) distributed in the upper Huaihe River should be nominated as S. y. yangtsekiense.(5) The S. yangtsekiense could be defined as two ESUs for conservation and management. Unit I consisted of the Yellow River populations (pops from 1 to 6) and the headstream of Huaihe River populations (pops from 7 to 9); Unit II included the remained populations of Huaihe River (pops from 10 to 20) and the whole Yangtze River populations (pops from 20 to 34).