Abstract:
BACKGROUND: Amblyomma spp. ticks, known for their long mouthparts, 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 intra-species variation of Amblyomma ticks collected in southern Africa, focusing on resolving the dispute
about A. pomposum and A. variegatum being distinct species.
METHODS: Four Amblyomma tick species were collected from Angola, Mozambique, South Africa, Zambia and Zimbabwe, and were identified morphologically as Amblyomma eburneum (208), A. hebraeum (4758), A. pomposum (191)
and A. variegatum (2577) using identification keys. Gene amplification targeting the 12S and 16S rRNA, cytochrome
oxidase I, cytochrome B and internal transcribed spacer-2 genes was conducted for 204 ticks, for which varying
success was achieved during amplification for each of the markers. Maximum likelihood analyses were performed
in IQ-TREE.
RESULTS: The phylogenetic topologies and ABGD analyses of each individual gene clustered A. pomposum
within the A. variegatum clade, while clearly separating A. eburneum and A. hebraeum from all other species. None
of the genetic markers indicated intraspecific structuring on the basis of geographical origin, despite great distances
between sampling sites.
CONCLUSION: Our study concludes 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 controversies. Furthermore, we propose mating and hybrid viability studies
between the two species to confirm their reproductive isolation.
