No abstract

Species with extensive geographic ranges may interact with different species assemblages at distant locations, with the result that the nature of the interactions may vary spatially. Black‐tailed prairie dogs Cynomys ludovicianus occur from Canada to Mexico in grasslands of the western Great Plains of North America. Black‐tailed prairie dogs alter vegetation and dig extensive burrow systems that alter grassland habitats for plants and other animal species. These alterations of habitat justify the descriptor “ecological engineer,” and the resulting changes in species composition have earned them status as a keystone species. We examined the impact of black‐tailed prairie dogs on small mammal assemblages by trapping at on‐ and off‐colony locations at eight study areas across the species' geographic range. We posed 2 nested hypotheses: 1) prairie dogs function as a keystone species for other rodent species; and 2) the keystone role varies spatially. Assuming that it does, we asked what are the sources of the variation? Black‐tailed prairie dogs consistently functioned as a keystone species in that there were strong statistically significant differences in community composition on versus off prairie dog colonies across the species range in prairie grassland. Small mammal species composition varied along both latitudinal and longitudinal gradients, and species richness varied from 4 to 11. Assemblages closer together were more similar; such correlations approximately doubled when including only on‐ or off‐colony grids. Black‐tailed prairie dogs had a significant effect on associated rodent assemblages that varied regionally, dependent upon the composition of the local rodent species pool. Over the range of the black‐tailed prairie dog, on‐colony rodent richness and evenness were less variable, and species composition was more consistent than off‐colony assemblages.

No abstract

Wildlife disease is recognized as a burgeoning threat to imperiled species and aspects of host and vector community ecology have been shown to have significant effects on disease dynamics. The black‐tailed prairie dog is a species of conservation concern that is highly susceptible to plague, a flea‐transmitted disease. Prairie dogs (Cynomys) alter the grassland communities in which they exist and have been shown to affect populations of small rodents, which are purported disease reservoirs. To explore potential ecological effects of black‐tailed prairie dogs on plague dynamics, we quantified flea occurrence patterns on small mammals in the presence and absence of prairie dogs at 8 study areas across their geographic range. Small mammals sampled from prairie dog colonies showed significantly higher flea prevalence, flea abundance, and relative flea species richness than those sampled from off‐colony sites. Successful plague transmission likely is dependent on high prevalence and abundance of fleas that can serve as competent vectors. Prairie dogs may therefore facilitate the maintenance of plague by increasing flea occurrence on potential plague reservoir species. Our data demonstrate the previously unreported ecological influence of prairie dogs on vector species assemblages, which could influence disease dynamics.

No abstract