Pathogens, parasites, and land-use change

Anthropogenic changes to landscapes are well known to have dramatic impacts on biodiversity, but the effects on inconspicuous members of biological communities, including parasites and pathogens, remain less well understood. In my lab, we are studying the relationship between land use change and disease in Colorado amphibians. We discovered that native leopard frogs in Colorado are declining in regions associated with invasive bullfrogs. Since then, we developed the hypothesis that ongoing land use change and associated impacts on natural and artificial water bodies influence the spread of invasive species (e.g., American bullfrogs, fish, and crayfish), some of which serve as reservoirs for amphibian disease. Graduate student Anna Peterson led a paper published in Biological Invasions, demonstrating that the creation of permanent water bodies in human dominated landscapes in the Front Range provide suitable habitat for the spread of invasive bullfrogs (Lithobates catesbeianus). We used extensive field surveys and a modeling approach to sort among competing hypotheses concerning the habitats favored by invasive bullfrogs. The bullfrogs act as a reservoir hosts for Bd which is linked to declines in amphibians globally. We then combined field surveys with lab experiments to delve deeper into the mechanisms by which bullfrogs may act as a reservoir of disease relative to native species. Thus, this work expands our understanding of how to identify a biotic reservoir of disease and is applicable to other pathogens that can transmit among many host species in natural systems.