Molecular Ecology Of Toad In Ningxia

Population genetic structure, historical biogeography, historical demography and effect of landscape on genetic differentiation of the alpine toad Scutiger ningshanensis were studied using the combined data mtDNA cytochrome b (cyt b) and the mtDNA cytochrome c oxidase subunit I (COI) as molecular markers. This species has high genetic variation. There was significant genetic differentiation among most populations. Three lineages were detected. The phylogenetic relationship analyses and the SAMOVA results showed significant phylogeographic structure.82.15% genetic variation was attributed to among populations while differentiation within populations only contributed 17.85% to the total. Mantel test results showed significant correlation between the pairwise calculated genetic distance and pairwise calculated geographical distance of the populations (regression coefficient=0.001286, correlation coefficient= 0.77051,p(rrand≥robs)= 0.0185<0.05), indicating the existence of isolation-by-distance pattern of genetic divergence for cyt b+COI sequence, which suggests that the distribution of genetic variation is due to geographical separation rather than to natural selection. The population expansion or contraction and genetic differentiation between populations or lineages could be explained by topography and the repetitive uplifts of the Tsinling Mountains and the climatic cycle during the late Pliocene and Pleistocene. S. ningshanensis experienced a rapid population expansion in about 40,000 years before present. The current decline in population size was probably caused by anthropogenic disturbance. Current populations of S. ningshanensis are from different refugia though the location of these refugia could not be determined in our study. Three genetic barriers were detected, one is between the localities hby+lfy and the locality nsc, another is between the locality nsc and the localities ljs+bys+srs, the third is between the locality ljs and the localities bys+srs. Topography is very important in shaping the genetic connectivity. Topography explains significantly more variation in genetic differentiation than IBD. Topography, climatic changes and repetitive population expansion/ contraction together led to the high level of genetic variation in S. ningshanensis. Three putative cryptic species were detected. A total of three management units (MUs) were determined, which must be considered when conservation policy is made in future.