title: Spatial scale modulates the strength of ecological processes driving disease distributions.
abstract: Humans are altering the distribution of species by changing the climate and disrupting biotic interactions and dispersal. A fundamental hypothesis in spatial ecology suggests that these effects are scale dependent; biotic interactions should shape distributions at local scales, whereas climate should dominate at regional scales. If so, common single-scale analyses might misestimate the impacts of anthropogenic modifications on biodiversity and the environment. However, large-scale datasets necessary to test these hypotheses have not been available until recently. Here we conduct a cross-continental, cross-scale (almost five orders of magnitude) analysis of the influence of biotic and abiotic processes and human population density on the distribution of three emerging pathogens: the amphibian chytrid fungus implicated in worldwide amphibian declines and West Nile virus and the bacterium that causes Lyme disease (Borrelia burgdorferi), which are responsible for ongoing human health crises. In all three systems, we show that biotic factors were significant predictors of pathogen distributions in multiple regression models only at local scales (∼10(2)-10(3) km(2)), whereas climate and human population density always were significant only at relatively larger, regional scales (usually >10(4) km(2)). Spatial autocorrelation analyses revealed that biotic factors were more variable at smaller scales, whereas climatic factors were more variable at larger scales, as is consistent with the prediction that factors should be important at the scales at which they vary the most. Finally, no single scale could detect the importance of all three categories of processes. These results highlight that common single-scale analyses can misrepresent the true impact of anthropogenic modifications on biodiversity and the environment.
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620; jcohen9@mail.usf.edu.
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Cohen
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: David J
authors.initials: DJ
authors.lastname: Civitello
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: Amber J
authors.initials: AJ
authors.lastname: Brace
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: Erin M
authors.initials: EM
authors.lastname: Feichtinger
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: C Nicole
authors.initials: CN
authors.lastname: Ortega
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: Jason C
authors.initials: JC
authors.lastname: Richardson
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: Erin L
authors.initials: EL
authors.lastname: Sauer
authors.affiliation: Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Integrative Biology, University of South Florida, Tampa, FL 33620;
authors.forename: Jason R
authors.initials: JR
authors.lastname: Rohr
mesh_terms: D000818:Animals; D044822:Biodiversity; D025065:Borrelia burgdorferi; D006801:Humans; D008193:Lyme Disease / Q000453:epidemiology* / Q000662:veterinary; D008954:Models, Biological; D014901:West Nile Fever / Q000453:epidemiology* / Q000662:veterinary; D014902:West Nile virus
keywords: Lyme disease; West Nile virus; chytridiomycosis; dilution effect; ecology