Population Genetics Of Partial Chinese

Rattus tanezumi is mainly distributed in the low-latitude regions of East and Southeast Asia. It is one of the most widespread house rats in China, mainly distributing in the Yangtze River Basin and to the south of the basin. In recent years, the distribution areas of R. tanezumi have expanded to Qinghai, Tibet and Xinjiang in the west, to Hebei and Liaoning in the north. R. tanezumi is harmful to human settlements, and it is a reservoir host of a variety of parasites, bacteria, rickettsia and ultraviruses. It spreads many important infectious diseases such as plague, leptospirosis, endemic typhus and hemorrhagic fever with renal syndrome (HFRS). The expansion of R. tanezumi’s distribution range will bring new threats to human health. We studied the population genetics of R. tanezumi in order to form a better understanding in the ecological characteristics of it, which provides a theoretical basis for the monitoring and control of the R. tanezumi.In this study, mitochondrial DNA and microsatellite makers were applied to examine genetic diversity, genetic structure and migration in25R. tanezumi populations, the results are as follows:(1) We built microsatellite-enriched library of R. tanezumi,13primer pairs were screened. The microsatellite makers were amplified by PCR using these13primer pairs in50samples from Shanghai and Chongqing, results showed that all of the microsatellite loci were highly polymorphic, and deviated from the Hardy-Weinberg equilibrium, this showed a state of heterozygote deficits in populations, but none of two loci displayed linkage disequilibrium. These microsatellite primers can be used in population genetics research in R. tanezumi as well as the other species of the same genus. (2) The analysis of mitochondrial DNA and microsatellite makers showed that the R. tanezumi populations of different geographical regions were different in genetic diversity. For COI sequences, the values of haplotype diversity (Hd) were from0.06061to0.79234, the values of nucleotide diversity(π) were from0.00009to0.00532; For D-loop sequences, the values of haplotype diversity (Hd) were from0.10000to0.88424and the nucleotide diversity (π) values were from0.00024to0.02165; The observed heterozygosity (Ho) values of microsatellite data ranged from0.497to0.708, expected heterozygosity (He) values were from0.656to0.890, the number of alleles per population was from5.15to15.15. The populations in Yunnan-Guizhou Plateau showed relatively high genetic diversity and genetic differentiation from other regions’ populations.(3)Both results of mitochondrial DNA and microsatellite makers revealed the natural environment impacted the population structure of R. tanezumi greatly. Complicated geographical environment of the Yunnan-Guizhou plateau separated its gene flow from other regions. The Qinghai-Tibet Plateau also showed the barrier effect. Due to the late formation time and convenient traffic, there was no barrier effect showed in Qiongzhou Strait. It almost had no correlation between genetic distance and geographic distance, the mode of gene flow in R. tanezumi was more inclined to the island model.(4) With the study of genetic distances and phylogenetic trees, R. tanezumi in Tibet region had a closer relationship with the one in Sichuan and Chongqing, it was likely to migrate through the Sichuan-Tibet Highway; R. tanezumi in Shijiazhuang had a closer phylogenetic relationship with the one in Yangtze River Basin, it was likely to spread by Beijing-Guangzhou railway and other transportation lines. R. tanezumi in Yunnan-Guizhou Plateau had an obvious differentiation with others, but in Leizhou and Yiwu, there were special haplotypes found, which also existed in Yunnan, there might be some uncertain factors in the migration among these regions, the R. tanezumi in Yunnan-Guizhou Plateau had some inherent relationships with these areas where plague had occurred.(5)The results of the mitochondrial DNA were not entirely consistent with microsatellite makers, such as the FST values. This pointed out that the comprehensive utilization of different molecular markers in analysis would be more accurate and efficient in the research of population genetics.We used mitochondrial DNA and microsatellite makers to analyse the relationship between genetic characteristics and geographic distribution of R. tanezumi in China, which laid the foundation for further study of the relationship between R. tanezumi and human health.