Parasites are often incapable of significant active dispersal, instead relying on hosts to facilitate movement and transmission. Seabirds are highly effective at long-distance dispersal, and their fidelity to large multi-species colonies exposes them to terrestrial ectoparasites such as the tick (Acari). The common seabird tick (Ixodes uriae) is one of the most widespread species in the world, suggesting the ectoparasites are moving freely among seabird colonies via aerial dispersal. Unlike most seabirds, however, penguins disperse primarily underwater. This presents a unique challenge for penguin-associated ticks, which are terrestrial yet must deal with the effects of seawater and pressure to disperse with their hosts. Here, we used next-generation sequencing to investigate phylogeographic structure and infer connectivity in little penguin (Eudyptula spp.) ticks (Ixodes spp.) on both fine (within a colony) and broad (among colonies across its range in Australia and New Zealand) scales. Physiological experiments were also carried out to test the physical limits of little penguin ticks in relation to the conditions they would face during marine dispersal, in order to ascertain whether underwater dispersal presents an effective barrier to tick movement. Results suggest that ticks may be able to withstand seawater emersion, that the extent of penguin social behaviour dictates fine-scale parasite population structure, and that trans-Tasman movements of little penguin ticks has occurred but remains too limited to maintain ongoing gene flow. We conclude that parasitic adaptations to harsh terrestrial conditions may confer survival in seemingly impossible environments.
Parasites are often incapable of significant active dispersal, instead relying on hosts to facilitate movement and transmission. Seabirds are highly effective at long-distance dispersal, and their fidelity to large multi-species colonies exposes them to terrestrial ectoparasites such as the tick (Acari). The common seabird tick (Ixodes uriae) is one of the most widespread species in the world, suggesting the ectoparasites are moving freely among seabird colonies via aerial dispersal. Unlike most seabirds, however, penguins disperse primarily underwater. This presents a unique challenge for penguin-associated ticks, which are terrestrial yet must deal with the effects of seawater and pressure to disperse with their hosts. Here, we used next-generation sequencing to investigate phylogeographic structure and infer connectivity in little penguin (Eudyptula spp.) ticks (Ixodes spp.) on both fine (within a colony) and broad (among colonies across its range in Australia and New Zealand) scales. Physiological experiments were also carried out to test the physical limits of little penguin ticks in relation to the conditions they would face during marine dispersal, in order to ascertain whether underwater dispersal presents an effective barrier to tick movement. Results suggest that ticks may be able to withstand seawater emersion, that the extent of penguin social behaviour dictates fine-scale parasite population structure, and that trans-Tasman movements of little penguin ticks has occurred but remains too limited to maintain ongoing gene flow. We conclude that parasitic adaptations to harsh terrestrial conditions may confer survival in seemingly impossible environments.
2B7 - Building 2 GSA2018_APCC6 GSACC62018@canberra.edu.au
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