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Microparasite species richness in rodents is higher at lower latitudes and is associated with reduced litter size

Bordes F., Guégan J.F., Morand S.. 2011. Oikos, 120 (12) : p. 1889-1896.

Parasite species loads are expected to be higher in the tropics and higher parasite species richness to have cumulative eff ects on host physiology or demography. Despite being regularly assumed or predicted, empirical evidence on species - latitude patterns is scarce or contradictory and studies on the impacts of concomitant infections have mainly been done at host intra-specifi c level. Broad generalizations are then very hard, if not spurious. By focusing on rodent species and their non-eukaryotic microparasites (i.e. viruses and bacteria), we investigated, using a comparative approach, microparasite species richness across rodent species according to the latitude where they occur. We also explored the links between rodents ' reproductive traits, latitude and microparasite species richness. We fi nd for the fi rst time in rodents that virus species richness increases towards tropical latitudes, and that rodent litter size seems to decrease when microparasite species richness increases independently from the latitude. Th ese results support the hypotheses that rodent species in the tropics eff ectively harbour higher parasite species loads, at least in terms of species richness for viruses, and that parasite species richness infl uences rodent life-history traits. Although some other factors, such as seasonality, were not taken into account due the lack of data, our study stresses the idea that chronic microparasite infections may have detrimental eff ects on their rodent host reservoirs, notably by aff ecting litter size. (Résumé d'auteur)

Mots-clés : bacteria; virus; vecteur de maladie; identification; enquête pathologique; yersinia pestis; leptospira; bartonella; borrelia; zone tropicale; transmission des maladies; poxviridae; arenaviridae; hantavirus; parasite; rongeur; orientia tsutsugamushi

Thématique : Organismes nuisibles des animaux; Maladies des animaux; Ecologie animale

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