Abstract
A comparative phylogeographic study on two economically important African tick species, Amblyomma hebraeum and Hyalomma rufipes was performed to test the influence of host specificity and host movement on dispersion. Pairwise AMOVA analyses of 277 mtDNA COI sequences supported significant population differentiation among the majority of sampling sites. The geographic mitochondrial structure was not supported by nuclear ITS-2 sequencing, probably attributed to a recent divergence. The three-host generalist, A. hebraeum, showed less mtDNA geographic structure, and a lower level of genetic diversity, while the more host-specific H. rufipes displayed higher levels of population differentiation and two distinct mtDNA assemblages (one predominantly confined to South Africa/Namibia and the other to Mozambique and East Africa). A zone of overlap is present in southern Mozambique. A mechanistic climate model suggests that climate alone cannot be responsible for the disruption in female gene flow. Our findings furthermore suggest that female gene dispersal of ticks is more dependent on the presence of juvenile hosts in the environment than on the ability of adult hosts to disperse across the landscape. Documented interspecific competition between the juvenile stages of H. rufipes and H. truncatum is implicated as a contributing factor towards disrupting gene flow between the two southern African H. rufipes genetic assemblages.
Highlights
Successful dispersal and the subsequent ability to reproduce with conspecifics are central to maintaining the integrity of sexually reproducing species [1]
A total of 115 adult A. hebraeum were collected from six localities in southern Africa and 162 adult H. rufipes were sampled from nine localities (Figure 1; Table 1)
The overall haplotype diversity (h) of 0.96 was much higher than that detected for A. hebraeum and ranged between 0.51 in a population from Stutterheim to 0.98 for the Garissa sampling site
Summary
Successful dispersal and the subsequent ability to reproduce with conspecifics are central to maintaining the integrity of sexually reproducing species [1]. Identifying the factors influencing the dispersal and genetic connectivity among tick populations of different geographic origin is not a trivial exercise and several hypotheses have been proposed. Key to the discussions are host specificity and the mobility of the hosts of adult ticks [1,6,7], the number and type of host species needed to complete the life cycle [8,9], sex-biased dispersal of different life stages [6,10], parasite-host immunity interactions [11] and abiotic factors associated with biogeographic barriers and other environmental changes [12,13,14,15,16]
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