Comparative mtDNA phylogeographic patterns reveal marked differences in population genetic structure between generalist and specialist ectoparasites of the African penguin (Spheniscus demersus).

To address factors affecting genetic diversity and dispersal of ectoparasites, we compared mitochondrial DNA (mtDNA) population genetic structures of the generalist soft tick Ornithodoros capensis to the more host-specific nest flea Parapsyllus humboldti. A total of 103 ticks and 92 fleas were sampled at five distinct South African island/mainland African penguin (Spheniscus demersus) colonies. With its wide host range, O. capensis showed no evidence of significant cytochrome c oxidase subunit I (COI) mtDNA population differentiation among the five sampling sites (φ = 0.00 ± 0.004; p = 0.80), as well as a higher level of genetic diversity (π = 0.8% ± 0.06%) when compared to P. humboldti. In contrast, the flea showed significant population structure among most of the same sampling sites (φ = 0.22 ± 0.11; p ≤ 0.05) and a lower level of genetic diversity (π = 0.2% ± 0.01%). Our findings suggest that despite both parasites being mostly nest bound, O. capensis have few barriers to dispersal among island and mainland colonies. However, P. humboldti are more dependent on the African penguin for dispersal and thus have more impediments to gene flow among the same colonies. These findings broadly support the SGVH (specialist generalist variation hypothesis) and provide the first evidence for this hypothesis in parasites restricted to seabird colonies.