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Certain parasite species have free-living stages, so habitat range may influence host-species range. We tested whether regional occurrence and habitat use of parasitic water mites were related to their host-species range. We collected 7445 Arrenurus Duges, 1834 mites from 7107 coenagrionid damselflies, representing 11 host species from 13 sites in southeastern Ontario and southwestern Quebec. Because larval water mites are difficult to identify morphologically to species, we chose to amplify the barcode fragment of cytochrome oxidase subunit I to explore host-species ranges. Fifteen operational taxonomic units or clades were identified based on the amplification from 217 larval mites. The Arrenurus clades that were present in both bog and marsh habitats had a broader host-species range than clades found only in marshes (the comparison with one clade found only in bogs lacked statistical power). As predicted, host-species range increased with the regional occurrence of an Arrenurus clade. Additionally, the most commonly barcoded species also have high host-species ranges. This result could be because species with broader host-species ranges are more common and were more likely to be sampled and barcoded (an explanation we favor), or due to sampling bias. Although this is the first study exploring whether habitat range affects host-species range, further investigation is needed to tease apart which habitat factors influence host-species ranges the most. Key words: host-parasite associations, Odonata, Coenagrionidae, Arrenuridae, host-species range. Certaines especes de parasites presentent des stades libres, de sorte que la gamme d'habitats peut influencer la gamme d'hotes. Nous avons verifie si la distribution regionale et l'utilisation des habitats d'hydrachnes parasites etaient reliees a leur gamme d'especes hotes. Nous avons preleve 7445 hydrachnes Arrenurus Duges, 1834 de 7107 demoiselles coenagrionides representant 11 especes hotes de 13 sites du sud-est de l'Ontario et du sud-ouest du Quebec. Etant donne la dificulte que presente l'affectation de larves d'hydrachnes a des especes precises sur la base de la morphologie, nous avons choisi d'amplifier le fragment code-barres de la sous-unite I de la cytochrome oxydase pour explorer les gammes d'hotes. Quinze unites taxonomiques operationnelles ou clades ont ete identifies sur la base de l'amplification a partir de 217 larves d'hydrachnes. Les clades d'Arrenurus presents dans les habitats tant de tourbiere que de marais avaient de plus grandes gammes d'especes hotes que les clades presents uniquement dans les marais (l'efficacite statistique de la comparaison avec un clade present seulement dans des tourbieres etait faible). Comme prevu, la gamme d'especes hotes augmentait en fonction de la presence regionale d'un clade d'Arrenurus. En outre, les especes les plus frequemment codees presentaient egalement de grandes gammes d'especes hotes. Cela pourrait etre du au fait que les especes presentant les plus larges gammes d'hotes sont plus repandues et etaient les plus susceptibles d'etre echantillonnees et codees (une explication que nous privilegions) ou a un biais d'echantillonnage. Bien qu'il s'agisse de la premiere etude a tenter de determiner si la gamme d'habitats a une incidence sur la gamme d'hotes, d'autres travaux sont necessaires pour departager les facteurs de l'habitat qui exercent la plus grande influence sur les gammes d'especes hotes. [Traduit par la Redaction] Mots-cles: associations hote-parasite, odonates, coenagrionides, arrenurides, gamme d'hotes., Introduction Many factors are thought to influence host specificity of parasites (Poulin 2007). Ecological factors are those that presumably affect encounter between the host and the parasite. These include spatial [...]

Abstract: Many animals respond behaviourally to the infective stages of parasites, but the efficacy of such responses in reducing risk of parasitism often is not established. It was found that [...]