Native vs. non-native grazers alter parasite assemblages but yield few changes in vegetation structure and mammalian community composition in a North American shortgrass prairie

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dc.contributor.advisorHamilton, Steven
dc.contributor.advisorMalaney, Jason
dc.contributor.advisorWoltmann, Stefan
dc.contributor.authorWilford, Caroline
dc.contributor.otherDepartment of Biology
dc.date.accessioned2020-03-23T14:12:26Z
dc.date.available2020-03-23T14:12:26Z
dc.date.issued2020
dc.date.updated2020-03-02T17:01:18Z
dc.description.abstractGrasslands are deteriorating globally resulting in widespread biodiversity degradation so understanding impacts of loss, or replacement, of native megaherbivores remains a central challenge for grassland conservation. Because of their disproportionately strong functional roles I compared native (bison) versus non-native (cattle) grazers in a shortgrass prairie from a multiyear field study by sampling 1,200 vegetation locations in two habitat types (grassland, woodland) across 48 transects (19,200 trap-nights) and collecting 5,127 parasites from 509 small mammals. I tested three competing hypotheses including top-down, bottom-up, and parasite centric models. Grazer differences appear to alter parasite community structure and composition despite lack of significant influences on vegetation and mammalian community structure and composition, thus favoring the parasite-centric hypothesis. Across parasites, nematode prevalence was significantly higher in bison-grassland sites (threefold increase, P=0.02) and marginally significant in bison-woodlands sites (tenfold increase, P=0.06). Flea prevalence was significantly higher in cattle-grasslands (twofold increase, P=0.03), but equivalent in woodlands. I failed to detect significant differences across treatment or habitats for cestode prevalence and all parasite intensities. These results highlight anthelmintic drugs may remain in the environment where they are encountered by nematodes. For my second chapter, because the relative importance of host versus environmental factors for explaining prevalence and intensity of flea parasitism in small mammals remains poorly understood, I evaluated these factors at two scales; among individuals of a single host species and across the landscape, sampling hosts from two habitat types (woodland and grassland). Using generalized linear models, I found host sex was an important predictor for parasites within a host (male-bias) for predicting both prevalence and intensity. Factors across hosts showed more variation. Host density and cattle treatment had a generally consistent, positive relationship with flea prevalence and intensity, but other factors such as vegetation and year had stochastic influences. Taken together, these results have implications for wildlife disease ecology because altered host and vector population abundances and composition are known drivers of pathogen transmission. Moreover, these combined results differ from tallgrass prairies, so land managers should consider alternative approaches to conserve distinct shortgrass prairies with different megaherbivores.
dc.identifier.otherOCLC #1147973423
dc.identifier.otherOCLC #1147973902
dc.identifier.urihttp://hdl.handle.net/20.500.11989/6701
dc.language.rfc3066en
dc.publisherAustin Peay State University
dc.subject.lcshGrassland conservation -- New Mexico
dc.subject.lcshHerbivores -- Losses -- New Mexico
dc.subject.lcshBiodiversity conservation
dc.subject.lcshPrairies -- New Mexico
dc.titleNative vs. non-native grazers alter parasite assemblages but yield few changes in vegetation structure and mammalian community composition in a North American shortgrass prairie

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