Recent evolution of host‐associated divergence in the seabird tick Ixodes uriae

Abstract

Ecological interactions are an important source of rapid evolutionary change and thus may generate a significant portion of novel biodiversity. Such changes may be particularly prevalent in parasites, where hosts can induce strong selection for adaptation. To understand the relative frequency at which host-associated divergences occur, it is essential to examine the evolutionary history of the divergence process, particularly when it is occurring over large geographical scales where both geographical and host-associated isolation may playa part. In this study, we use population genetics and phylogeography to study the evolutionary history of host-associated divergence in the seabird tick Ixodes uriae (Acari, Ixodidae). We compare results from microsatellite markers that reflect more ecological timescales with a conserved mitochondrial gene (COIII) that reflects more ancient divergence events. Population structure based on microsatellites showed clear evidence of host-associated divergence in all colonies examined. However, isolated populations of the same host type did not always group together in overall analyses and the genetic differentiation among sympatric host races was highly variable. In contrast, little host or geographical structure was found for the mitochondrial gene fragment. These results suggest that host race formation in I. uriae is a recent phenomenon, that it may have occurred several times and that local interactions are at different points in the divergence process. Rapid divergence in I. uriae implies a strong interaction with its local host species, an interaction that will alter the ecological dynamics of the system and modify the epidemiological landscape of circulating micropathogens.

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

“…Ticks that exploited Adélie penguins were present in the most south-western and the most north-eastern colonies sampled, and were strongly differentiated, whereas ticks sampled from gentoo penguins in the HANN colony were genetically similar to those from Adélie penguins in the PALM and DREA colonies. This contrasts with patterns found in the northern hemisphere (McCoy et al 2001, 2005b, Kempf et al 2009) and on NEWI (present study), where sympatrically occurring seabird species tend to have distinct tick populations. However, no genetic structure was found between tick populations exploiting closely related Eudyptes spp.…”

“…To examine tick genetic diversity and population structure, ticks were genotyped at 8 microsatellite markers previously developed and used for this species (McCoy & Tirard 2000). DNA amplifications and allele size determination were carried out as previously described in Kempf et al (2009) and Dietrich et al (2012).…”

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.…”

Seabirds and the Circulation of Lyme Borreliosis Bacteria in the North Pacific

“…Alternatively, differences in seroprevalence may be due to host specialisation in tick vector. In the North Atlantic and sub-Antarctic, evidence of host-associated genetic structure has been found for I. uriae , 2005b, Kempf et al 2009), along with differences in Borrelia prevalence and intensity among sympatrically occurring tick races (Duneau et al 2008, Gó mez-Diaz et al 2010. Information on the population genetic structure of I. uriae within North Pacific colonies will be now required to test the potential role of vector specialisation in determining patterns of Bbsl exposure.…”