Molecular Phylogeography Of Meriones Meridianus And Meriones Unguiculatus

Meriones meridianus and Meriones unguiculatus are indicator species of biodiversity of Mongolian-Xinjiang animal region. And distribution ranges are extensive, especially M. meridianus. Therefore, they can be perfect study object when we studied phylogeography of minitype mammal distributed in Mongolian-Xinjiang region. We Analyzed the genetic variation and geographical distribution of genealogical lineages of M. meridianus and M. unguiculatus using the complete mitochondrial cytochrome-b gene, to investigate the effects of historical tectonic and climate change in Quaternary ice ages on the intraspecific diversity and evolution of Mongolian-Xinjiang region small mammals.In this study, we sequenced the complete mitochondrial cytochrome-b gene(1140 bp) for 77 M.meridianus individuals and 52 M.unguiculatus individuals.in order to investigate geographical distribution of genealogical lineages and population history of M.meridianus and M.unguiculatus. The results were as follows:(Ⅰ) Phylogeography of Meriones meridianus1. Within the the complete mitochondrial Cyt b gene sequences of 77 individuals, two hundred and twelve variable sites were found, including 179 transitions and 33 transversions. 59 haplotypes were defined from 77 individuals. Haplotype diversity(H) and nucleotide diversity(π) was 0.991 and 0.047, respectively.2. Phylogenetic tree analyses(NJ method and MP method) demonstrated that all the haplotypes can be arranged into three highly supported groups: Tianshan group, Southeast group and Northwest group. Three groups of M. meridianus were estimated to diverge at 1.46～2.18 Mya. And F-statistics test for Pairwise population detected significantly distinctive geographic phylogeography among 3 groups(P<0.01). Taklimakan Desert may constitute geographic barriers for M.meridianus.3. A unimodal mismatch distribution of the Southeast group has been observed, and the Tajima's D test and Fu test are all significantly negative(D=-2.005, P<0.05 and Fs=-25.045, P<0.05). These testes suggested the population expansion of the Southeast group and this expansion was estimated to occur about 83, 000 years ago during the last interglaciation stage.(Ⅱ) Phylogeography of Meriones unguiculatus1. Within the the complete mitochondrial Cyt b gene sequences of 52 individuals, 74 variable sites were found, including 65 transitions and 9 transversions. 37 haplotypes were defined from 52 individuals. Haplotype diversity(H) and nucleotide diversity(π) was 0.976 and 0.007 respectively.2. Phylogenetic tree analyses(NJ method and MP method) demonstrated that all the haplotypes can be arranged into two highly supported Clades(Clade A and Clade B). Clade B consists of tree haplotypes from the Eastern Helan Mountains population and Clade A includes the remaining haplotypes from this population and the other 5 populations. The time of the common ancestor of the M. unguiculatus was estimated to be 260,000 years ago, indicating that there was a severe bottleneck effect on M.unguiculatus during the Lushan glacier in late Pleistocene. And the Eastern Helan Mountains might have reserved as a glacial refugium and harbored both distinct lineages.3. A unimodal mismatch distribution of the Clade A has been observed, and the Tajima's D test and Fu test are all significantly negative(D=-1.86, P<0.05 and Fs=-21.89, P<0.05). These testes suggested the single population expansion of M. unguiculatus and this expansion was estimated to occur about 110,000 years ago during the last interglaciation stage.(Ⅲ) Divergence time of Meriones meridianus and Meriones unguiculatus Base on 59 haptypes of M.meridianus and 37 haptypes of M.unguiculatus, Phylogenetic tree analyse(MP method) demonstrated that all the haplotypes can be arranged into two highly supported groups. The time of the most recent common ancestor of M.meridianus and M.unguiculatus was estimated to be 2.73Mya.