Crossbreeding between different geographical populations of the brown dog tick, Rhipicephalus sanguineus (Acari: Ixodidae)

Brown dog ticks are distributed world-wide, and their systematics and phylogeny are the subject of an ongoing debate. The present study evaluates the reproductive compatibility between Rhipicephalus sanguineus ticks from North America, Israel, and Africa. Female ticks of the parent generation were mated with males from the same and alternate colonies. Every pure and hybrid cohort was maintained separately into the F2 generation with F1 females being allowed to mate only with males from the same cohort. The following survival parameters were measured and recorded for every developmental stage: feeding duration and success; engorgement weight, fertility, and fecundity of females; molting and hatching success. Ticks from North American and Mediterranean populations hybridized successfully. The survival parameters of all their hybrid lines were similar to those in pure lines throughout the F1 generation, and F1 adults were fully fertile. Parent adult ticks from the African population hybridized with either North American or Mediterranean ticks and produced viable progenies whose survival parameters were also similar to those in pure lines throughout the F1 generation. However, F1 adults in the four hybrid lines that included African ancestry were infertile. No parthenogenesis was observed in any pure or hybrid lines as proportion of males in F1 generation ranged from 40 to 60 %. Phylogenetic analysis of the 12S rDNA gene sequences placed African ticks into a separate clade from those of the North American or Mediterranean origins. Our results demonstrate that Rh. sanguineus ticks from North America and Israel represent the same species, whereas the African population used in this study is significantly distant and probably represents a different taxon.