DNA barcoding of tick species (Archnida: Ixodida) to support species identification and discovery of cryptic genetic diversity with emphasis on the British fauna

Ticks are of medical and veterinary concern due to their role as vectors of a wide range of pathogens, including viruses, protozoa, and bacteria. Accurate species identification is essential during tick surveillance and disease control programmes, as certain pathogens are associated with particular tick species. In this study, genetic variation of a partial sequence of the cytochrome c oxidase I (COI) gene was used for molecular identification of tick species to corroborate morphological identification. This also enabled investigation of cryptic diversity within tick species. Thirty species belonging to the genera Amblyomma, Argas, Carios, Dermacentor, Haemaphysalis, Hyalomma, Ixodes, Ornithodoros, and Rhipicephalus were assessed. Tree-topology analysis confirmed discrete clustering of specimens according to species for the majority of taxa. Intraspecific genetic divergence ranged from 0 to 6.08%. In taxa where species complexes are known, separation of discrete groups were found. Several species yielded >2% intraspecific genetic divergence when compared to other taxa, suggesting potential cryptic diversity. DNA barcoding was an effective approach for the morphological identification of UK and non-native ticks, and for the detection of cryptic diversity within species.