Comparative analysis of mitochondrial markers from four species of Rhipicephalus (Acari: Ixodidae)

Mitochondrial sequences of four mitochondrial markers: 12S rRNA, 16S rRNA, cytochrome c oxidase subunit I (COX1) and cytochrome b (CytB) from four Rhipicephalus species were analyzed to establish genetic relationships and enable molecular identification. Field-collected samples from the species Rhipicephalus annulatus, Rhipicephalus bursa, Rhipicephalus sanguineus and Rhipicephalus turanicus were amplified by PCR and compared with GenBank™ annotated sequences. PCR products were obtained using primers that were designed to amplify orthologous sequences from different tick species and genera. The average intra-species sequence identity was 98.5-99.5%, while the average inter-species identity was 86.5-89.6%, reflecting a ≈ 10% decrease in the identity, when different species are compared. The "closest" two species, in terms of sequence identity, were R. sanguineus and R. turanicus, while the "least close" ones were R. annulatus and R. sanguineus. Molecular identification of each species was accomplished by a combined restriction analysis of 12S, COX1 and CytB markers, obviating the need for field sample sequencing. The restriction mapping data suggest that by using several markers, each with a unique digestion pattern, the identity of a given sample could be determined at the species level. It is anticipated that with the accumulation of more information on additional species and markers, molecular identification will become a standard approach for tick classification, complementing morphological taxonomy.