Population genetic structure and colonisation of the western Antarctic Peninsula by the seabird tick Ixodes uriae

Abstract

Recent observations on the western Antarctic Peninsula have suggested that changing climatic conditions may be increasing pressure on breeding seabirds due to higher exploitation rates by the tick Ixodes uriae. Using data from 8 microsatellite markers and ticks from 6 Pygoscelis spp. colonies, we employed a population genetics approach to specifically test the hypothesis that I. uriae is expanding south-westward along the peninsula from the Subantarctic region. Contrary to expectations, tick genetic diversity was high within all colonies, and no remaining signal of colonisation events was evident. Although significant geographic genetic structure occurred among ticks from different colonies, these ectoparasites tended to belong to 2 major genetic groups, one found principally in south-western locations (Palmer Station area) and the other in more north-eastern areas (South Shetland Islands). More central colonies showed a mixture of ticks from each genetic group, suggesting that this area represents a hybridisation zone of ticks from 2 distinct origins. A subsequent clustering analysis, including ticks from 2 Subantarctic locations, did not reveal the source population for the northern peninsula group. Overall, our data refute the hypothesis of a recent south-westward expansion of I. uriae along the peninsula and suggest that this tick has been present at more southern latitudes for an extended period of time. Further studies on the distribution and genetic characteristics of this ectoparasite around Antarctica are now required to better understand the colonisation process and predict how changing environmental conditions may affect its presence and diversity in seabird colonies.

Thirty years of tick population genetics: A comprehensive review

“…Recent development of host races within nesting colonies Dietrich et al (2012aDietrich et al ( ,b, 2013Dietrich et al ( , 2014, Kempf et al (2009a), McCoy et al (1999, McCoy and Tirard (2000), McCoy et al (2001McCoy et al ( , 2003aMcCoy et al ( ,b, 2005bMcCoy et al ( , 2012, McCoy andTirard (2000, 2002) Rhipicephalus annulatus…”

“…The exploration of population structure and host race formation in Ixodes uriae is the most comprehensive body of work in tick population genetics (Dietrich et al, , 2014(Dietrich et al, , 2012bKempf et al, 2009a;McCoy et al, 2012McCoy et al, , 1999McCoy et al, , 2005aMcCoy et al, , 2001McCoy et al, , 2003aMcCoy et al, , 2005bMcCoy andTirard, 2000, 2002;McCoy et al, 2003b). This species is part of the I. ricinus complex and a vector of the Lyme disease pathogen, B. burgdorferi.…”

Host specialization in ticks and transmission of tick-borne diseases: a review

“…After observing asynchrony in the timing of tick exploitation on different sympatric seabird species, McCoy et al (1999) hypothesized that I. uriae populations may consist of a series of local host-specific groups. They tested the predictions of this hypothesis using a population genetic approach with specifically-developed microsatellite markers (McCoy and Tirard, 2000) and found that throughout the different zones of its global distribution, this tick had indeed formed host-specific genetic groups (or host races) and that these host races had evolved independently in different isolated regions (McCoy et al, 2001, 2005, 2012; Dietrich et al, 2012). This divergence has been suggested to be relatively recent (Kempf et al, 2009a), but has been accompanied by both phenotypic changes in body morphology (Dietrich et al, 2013) and host-associated variation in performance on different host species (Dietrich, 2011).…”

Tandem host‐parasite dispersal inferred from similarities in phylogeographical patterns among Little Penguins and their ‘terrestrial’ ectoparasites

“…albatross and shags) when they breed in sympatry (McCoy et al, ), and that life history can influence the level of host specificity and thus dispersal of seabird parasites (Wessels, Matthee, Espinaze, & Matthee, ). However, host specificity was not evident between three penguin species in the western Antarctic Peninsula (McCoy et al, ), nor among two related species of penguin in the Crozet Archipelago (McCoy, Chapuis, et al, ), nor among the two recently split Little Penguin species (this study), suggesting that ticks might readily be shared among penguin species. The present study also suggests—although based on a single specimen—that New Zealand penguin species (Little and yellow‐eyed penguins) may share ticks.…”