Background: Anticoagulant rodenticide (AR) resistance in the Asian house rat (Rattus tanezumi) poses significant challenges to rodent control in China, reducing efficacy of ARs and increasing environmental contamination risks to nontarget species. Although Vkorc1 mutations confer resistance in rodents, their prevalence and evolutionary origins have remained unclear in most R. tanezumi populations in China.
Results: We sequenced the mitochondrial Cyt b, D-loop and Vkorc1 genes in different R. tanezumi populations. Phylogenetic analysis confirmed all sampled individuals were exclusively R. tanezumi, rejecting the hypothesis of Vkorc1 introgression from Rattus rattus. We identified two resistance-conferring Vkorc1 mutations (Y139C and A26T) occurring on four distinct haplotypes, indicating multiple independent evolutionary origins of resistance. Crucially, a star-like D-loop network and neutrality tests indicated a demographic expansion of R. tanezumi populations in southern China. This expansion is likely to have driven the northward dispersal of a predominant Y139C-carrying haplotype, facilitating the rapid establishment of resistant populations in northern China. Thus, although both independent evolution and population dispersal shaped the spatial distribution of resistant Vkorc1 mutations, dispersal emerged as the predominant force.
Conclusion: This study identifies two Vkorc1 mutations as valuable genetic markers for monitoring anticoagulant rodenticide resistance in R. tanezumi. Our findings provide critical insights into the evolution and spread of Vkorc1 resistance, revealing the significant role of recent population expansion and northward dispersal of a key resistant haplotype in establishing resistance across China. These results also underscore the urgent need for effective management strategies targeting resistant R. tanezumi populations. © 2025 Society of Chemical Industry.
Keywords: D‐loop; Rattus tanezumi; Vkorc1; anticoagulant; polymorphism; resistance.
© 2025 Society of Chemical Industry.