Comparative phylogeography of two commensal rat species (Rattus tanezumi and Rattus norvegicus) in China: Insights from mitochondrial DNA, microsatellite, and 2b-RAD data

Rattus norvegicus and Rattus tanezumi are dominant species of Chinese house rats, but the colonization and demographic history of two species in China have not been thoroughly explored. Phylogenetic analyses with mitochondrial DNA including 486 individuals from 31 localities revealed that R. norvegicus is widely distributed in China, R. tanezumi is mainly distributed in southern China with currently invading northward; northeast China was the natal region of R. norvegicus, while the spread of R. tanezumi in China most likely started from the southeast coast. A total of 123 individuals from 18 localities were subjected to 2b-RAD analyses. In neighbor-joining tree, individuals of R. tanezumi grouped into geographic-specific branches, and populations from southeast coast were ancestral groups, which confirmed the colonization route from southeast coast to central and western China. However, individuals of R. norvegicus were generally grouped into two clusters instead of geographic-specific branches. One cluster comprised inland populations, and another cluster included both southeast coast and inland populations, which indicated that spread history of R. norvegicus in China was complex; in addition to on-land colonization, shipping transportation also have played great roles. ADMIXTURE and principal component analyses provided further supports for the colonization history. Demographic analyses revealed that climate changes at similar to 40,000 to 18,000 years ago and similar to 4000 years ago had led to population declines of both species; the R. norvegicus declined rapidly while the population of R. tanezumi continuously expanded since similar to 1500 years ago, indicating the importance of interspecies' competition in their population size changes. Our study provided a valuable framework for further investigation on phylogeography of two species in China.

Automated summary

The colonization and demographic history of Chinese house rats, Rattus norvegicus and Rattus tanezumi, have been explored using mitochondrial DNA and 2b-RAD analyses. R. norvegicus is widely distributed in China, while R. tanezumi is mainly distributed in the south, currently invading northward. The colonization route of R. tanezumi started from the southeast coast, while R. norvegicus had a complex spread history involving both on-land colonization and shipping transportation. Climate changes and interspecies competition were important factors influencing the population size changes of both species. This study provides a valuable framework for further investigation on the phylogeography of these two species in China.