Studies On Genetic Structure And Phylogeny Of Parasitic Unionicolid Mites (Acari: Unionicolidae: Unionicola) Based On Mitochondrial 12S RRNA Gene

In the present study, Partial sequences of mitochondrial DNA 12S rRNA gene of 29 samples including eight species of unionicolid mites in the freshwater bivalves and a free-living Eylais galeata were sequenced. These water mites were collected from the main lakes (Poyang Lake, Chaohu Lake, Taihu Lake, Dongting Lake, Liangzihu Lake and Baoanhu Lake) on the low and middle reaches of the Yangtze River. All these 12S rRNA sequences data were used to analyze the phylogenetic relationship and population genetic structure of parasitic unionicolid mites. Nucleotide sequences were rich in A and T. Phylogenetic trees of unionicolid mites were reconstructed with a free-living Eylais galeata as outgroup by Phylip and MEGA soft. The topology structure of these phylogenetic trees was similar. Every species of unionicolid mites were separated with high values of bootstrap. The phylogenetic analysis of unionicolid mites indicated that the mitochondrial DNA 12S rRNA gene may be a suitable molecular maker to analyze the interspecific and /or intraspecific phylogenetic relationship of Unionicola. U. arcuata which was at the end of the phylogenetic tree and farther than other unionicolid mites from the outgroup species. The results revealed that the U. arcuata was relatively evolutionary species, as the clustering locality in phylogenetic tree was more distance between the unionicolid mites and the outgroup. U. imamurai is relatively original species, because it was more closed the outgroup species than other mites. In addition, U. formosa and U. ypsilophora were belong to the same subgenus in classic taxology, they was supported by high bootstrap and were also clustered together in phylogenetic tree.The indexs of the Nst, Fst and Nm were used to analyze the genetic structure of U. arcuata by mitochondrial partial 12S rRNA gene sequences. U. arcuata were separated into three groups, following by being associated with host (C. plicata, A. woodiana elliptica, A.woodiana pacified). The Nst values varied from 0.94721 to 0.99000 ( 0.94721, 0.97504, 0.99000) among these groups, and indicated that the genetic divergence was very high between these groups. The Fst values among these groups ranging from 0.94488 to 0.98930 suggested that the population genetic subdivision is very significant. The Nm values varied from 0.003 to 0.015, and indicated that major factor of population genetic diversity was induced for genetic drift.