Wessels C, Matthee S, Espinaze M P A, Matthee C A
Evolutionary Genomics Group, Department of Botany and Zoology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
Department of Conservation Ecology and Entomology, Faculty of AgriScience, Stellenbosch University, Private Bag X1, Stellenbosch, 7602, South Africa.
Parasitol Res. 2019 Feb;118(2):667-672. doi: 10.1007/s00436-018-6150-x. Epub 2018 Nov 21.
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.
为了探究影响体外寄生虫遗传多样性和扩散的因素，我们比较了泛食性软蜱卡氏钝缘蜱（Ornithodoros capensis）与宿主特异性更强的巢蚤洪氏副蚤（Parapsyllus humboldti）的线粒体DNA（mtDNA）群体遗传结构。在南非五个不同的岛屿/非洲大陆企鹅（斑嘴环企鹅，Spheniscus demersus）栖息地共采集了103只蜱和92只蚤。卡氏钝缘蜱宿主范围广泛，在五个采样点之间未发现细胞色素c氧化酶亚基I（COI）mtDNA群体有显著分化（φ = 0.00 ± 0.004；p = 0.80），并且与洪氏副蚤相比，其遗传多样性水平更高（π = 0.8% ± 0.06%）。相比之下，蚤在大多数相同采样点之间表现出显著的群体结构（φ = 0.22 ± 0.11；p ≤ 0.05），遗传多样性水平较低（π = 0.2% ± 0.01%）。我们的研究结果表明，尽管这两种寄生虫大多局限于巢穴，但卡氏钝缘蜱在岛屿和大陆栖息地之间的扩散几乎没有障碍。然而，洪氏副蚤在扩散方面对非洲企鹅的依赖性更强，因此在相同栖息地之间的基因流动存在更多阻碍。这些发现广泛支持了专家泛化变异假说（SGVH），并为该假说在局限于海鸟栖息地的寄生虫中提供了首个证据。
