Ecotones are transition zones between two different habitats. Ecotones frequently have a higher number of free-living species than the adjacent habitats. Increased ecotone diversity may be a consequence of habitat heterogeneity that allows species from different habitats to co-occur with species endemic to the ecotone. The effect of ecotones on parasite diversity, however, remains largely unknown. Ecotones may be places of high diversity where parasite species from adjacent habitats co-occur with parasites endemic to the ecotone. Parasites may also be more prevalent or have higher intensities in ecotones because of overlapping host ranges and abundance. Here, we test the hypothesis that ecotones will have higher species richness, prevalence, and intensity of parasites than in adjacent habitats. We compare parasite communities of North American deer mice (Peromyscus maniculatus) across sagebrush–ecotone–pinyon-juniper habitat gradients in the Great Basin. We sampled mice from four locations with three habitats per location (sagebrush, ecotone, pinyon-juniper). In each habitat, we sampled 25 mice (75 mice/location). Gastrointestinal tracts were dissected for helminths and individuals were combed for ectoparasitic arthropods (e.g. ticks, mites, fleas, and lice). Parasites were identified to morphospecies. Parasite species richness, prevalence, and intensity were compared among habitats.
Results/Conclusions
Our data indicate differences in parasite communities among the three habitats. Out of 337 deer mice, 86% were infected by at least one parasite species. We found no increase in species richness, prevalence, or intensity of parasites in the ecotone compared to adjacent sagebrush and pinyon-juniper habitats. Regression models indicate that parasite prevalence is best predicted by body mass and location rather than habitat type. We found that location was a better predictor of flea and tick prevalence than habitat, whereas louse prevalence was best predicted by body mass and did not differ among habitat or location. Habitat, location, and mass were not significant predictors of tick, louse, and helminth intensity. Habitat appears to be the least important factor determining prevalence and intensity of most parasites. However, the intensity of fleas, the most prevalent arthropod, differed among locations and habitats. Flea intensity was significantly higher in sagebrush habitats than in ecotones and pinyon-juniper. Interestingly, the prevalence of pinworms (Syphacia peromysci), the most prevalent helminth, was significantly lower in sagebrush than in ecotones and pinyon-juniper. Future work will examine how parasite co-infection and competition leads to patterns of parasite distribution in the Great Basin, especially the interaction between fleas and pinworms.