Intra- and Interspecific variation of Amblyomma ticks from southern Africa

Abstract

Amblyomma spp. ticks, known for their bright ornate appearance and aggressive hunting behaviour, are vectors of a number of important pathogens. In southern Africa, 17 Amblyomma spp. are currently documented. Of these species, Amblyomma hebraeum and Amblyomma variegatum have been well studied due to their wide geographical range and their status as competent vectors of pathogens that are of veterinary and medical importance. Studies on other Amblyomma spp. in southern Africa have been neglected, fostering ongoing debates on the validity of certain species such as Amblyomma pomposum. This study investigated the inter- and intraspecies variation of Amblyomma ticks collected in southern Africa, focusing on resolving the dispute about A. pomposum and A. variegatum as distinct species. Four tick species were collected from Angola, Mozambique, South Africa, Zambia, and Zimbabwe and were identified morphologically as Amblyomma eburneum, A. hebraeum, A. pomposum and A. variegatum using identification keys. Gene amplification was done targeting the 12S and 16S rRNA, cytochrome oxidase I, cytochrome B and internal transcribed spacer-2 genes, and Bayesian inference analyses were performed in MrBayes. These revealed little geographic structuring amongst ticks of the same species from different countries, although intraspecific variation within A. variegatum was high for the 16S and cytB loci. Our study concluds that there is insufficient molecular evidence to differentiate A. pomposum and A. variegatum from each other. We highlight the need for whole mitochondrial genome sequencing of these two species to resolve the ongoing debates. Furthermore, we propose mating and hybrid viability studies between the two species to confirm their reproductive isolation.