Dietrich M. auteur aut IRD Beati L. auteur aut IRD Elguero Eric auteur aut IRD Boulinier T. auteur aut IRD McCoy K. D. auteur aut IRD text journalArticle eng text/pdf born digital access The tick Ixodes uriae is a common ectoparasite of seabirds, and is widely distributed across the circumpolar regions of both hemispheres. Previous work demonstrated the existence of genetically distinct host races of this ectoparasite, occurring across its current range. The objective of the present study was to examine whether these host races have evolved measurable morphological differences. We measured a set of morphological variables on 255 non-engorged ticks (nymphs and adults) collected from three sympatrically occurring host species in the North Atlantic. Genotyping at eight microsatellite markers enabled us to analyse the relationship between patterns of morphological and neutral genetic variation. Multivariate analyses showed that most morphological variation was associated with size differences among tick individuals. Body size differed among races, but only in adult life stages. A linear discriminant analysis based on shape variation revealed three distinct morphological clusters corresponding to the three tick host races. These results, along with correlated patterns of host-related genetic variation, suggest that differences among host-related groups are not simply the result of phenotypic plasticity or drift, but rather reflect host-associated adaptations. Experimental work and observations across the range of I.?uriae will now be required to test the genetic basis and adaptive nature of morphological differences. specialized adaptation bird morphometry parasite sympatric speciation NORVEGE 052 080 020 108 2 323-334 2013 0024-4066 https://www.documentation.ird.fr/hor/fdi:010058950 10.1111/j.1095-8312.2012.02021.x 0024-4066 [F B010058950] https://www.documentation.ird.fr/hor/fdi:010058950 https://www.documentation.ird.fr/intranet/publi/2013/02/010058950.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2013-03-06 2017-08-23 fdi:010058950 fre