Host-associated differentiation in Dermacentor variabilis

The American dog tick, Dermacentor variabilis, a primary vector of tularemia and Rocky Mountain spotted fever. D. variabilis feeds on a wide variety of hosts. Usually the larval and nymphal stages feed on small mammals such as mice and the adults feed on medium sized mammals such as raccoons and dogs. Genetic variation in this tick could be associated with host species. The existence of genetically distinct populations associated with host species is called host associated differentiation, HAD. In this study, ticks were collected from different vertebrate hosts to test for HAD using SNPs. DNA extractions were optimized for ddRADseq Illumnia Novasequencing. It was found that D. variabilis is exhibiting moderate to very great HAD. D. variabilis was genetically distinct on wild board and on harvest mice when compared to all other groups. There was no HAD when comparing three other mouse species. We hypothesize this might be due to the nesting habits of the different hosts as the genetic differentiation varied accordingly. These results shed light on strategies for tick control because understanding the population structure of these ticks will aid in targeted pest control methods.