Habitat loss, fragmentation, and the relationship between biodiversity loss and infectious disease dynamics
The dilution effect hypothesis, which states that increased diversity leads to a reduction of infectious disease transmission or transmission risk, has guided empirical studies of host diversity-disease relationships, but its predictions conflict with some empirical results and have been the subject of considerable academic debate. We present a theoretical framework to explore how habitat fragmentation impacts pathogen prevalence and persistence within fragmented habitats among a diverse assemblage of species. Model parameters are scaled by body size and community assemblage is determined by patch size and individual population density responses to patch size (i.e. edge specialist vs. core habitat specialist).
Infections of a single host species are significantly affected by patch size and can be fit to data observed in some taxa over a range of fragmentation (increasing prevalence of pathogens with patch size, observed in avian species). However, species assemblages and the degree of habitat fragmentation impact the prevalence and persistence of generalist pathogens. The framework developed here can be modified to specific pathogen systems to provide predictions of disease dynamics following habitat fragmentation that can be useful in testing predictions of the how host community structure impacts disease transmission in changing landscapes.