title: Recurrent evolution of host-specialized races in a globally distributed parasite.
abstract: The outcome of coevolutionary interactions is predicted to vary across landscapes depending on local conditions and levels of gene flow, with some populations evolving more extreme specializations than others. Using a globally distributed parasite of colonial seabirds, the tick Ixodes uriae, we examined how host availability and geographic isolation influences this process. In particular, we sampled ticks from 30 populations of six different seabird host species, three in the Southern Hemisphere and three in the Northern Hemisphere. We show that parasite races have evolved independently on hosts of both hemispheres. Moreover, the degree of differentiation between tick races varied spatially within each region and suggests that the divergence of tick races is an ongoing process that has occurred multiple times across isolated areas. As I. uriae is vector to the bacterium responsible for Lyme disease Borrelia burgdorferi sensu lato, these results may have important consequence for the epidemiology of this disease. With the increased occurrence of novel interspecific interactions due to global change, these results also stress the importance of the combined effects of gene flow and selection for parasite diversification.
authors.affiliation: Queen's University, Department of Biology, Kingston, Ontario, Canada K7L 3N6. mccoy@mpl.ird.fr
authors.forename: Karen D
authors.initials: KD
authors.lastname: McCoy
authors.forename: Elodie
authors.initials: E
authors.lastname: Chapuis
authors.forename: Claire
authors.initials: C
authors.lastname: Tirard
authors.forename: Thierry
authors.initials: T
authors.lastname: Boulinier
authors.forename: Yannis
authors.initials: Y
authors.lastname: Michalakis
authors.forename: Céline Le
authors.initials: CL
authors.lastname: Bohec
authors.forename: Yvon Le
authors.initials: YL
authors.lastname: Maho
authors.forename: Michel
authors.initials: M
authors.lastname: Gauthier-Clerc
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000469:parasitology*; D019143:Evolution, Molecular; D006790:Host-Parasite Interactions; D013045:Species Specificity; D013987:Ticks / Q000145:classification* / Q000235:genetics* / Q000502:physiology