Heterogeneity in patch quality buffers metapopulations from pathogen impacts
Many wildlife species persist on a network of ephemerally occupied habitat patches connected by dispersal. Provisioning of food and other resources for conservation management or recreation is frequently used to improve local habitat quality and attract wildlife. Resource improvement can also facilitate local pathogen transmission, but the landscape-level consequences of provisioning for pathogen spread and habitat occupancy are poorly understood. Here, we develop a simple metapopulation model to investigate how heterogeneity in patch quality resulting from resource improvement influences long-term metapopulation occupancy in the presence of a virulent pathogen. We derive expressions for equilibrium host–pathogen outcomes in terms of provisioning effects on individual patches (through decreased patch extinction rates) and at the landscape level (the fraction of high-quality, provisioned patches), and highlight two cases of practical concern. First, if occupancy in the unprovisioned metapopulation is sufficiently low, a local maximum in occupancy occurs for mixtures of high- and low-quality patches, such that further increasing the number of high-quality patches both lowers occupancy and allows pathogen invasion. Second, if the pathogen persists in the unprovisioned metapopulation, further provisioning can result in all patches becoming infected and in a global minimum in occupancy. This work highlights the need for more empirical research on landscape-level impacts of local resource provisioning on pathogen dynamics.
KeywordsConservation biology Infectious disease Habitat management Metapopulation Resource provisioning Supplemental feeding Mathematical modeling Source–sink dynamics
We thank Sonia Altizer, Alexandra Bentz, members of the Altizer and Ezenwa labs at the University of Georgia, and two anonymous reviewers for helpful comments on earlier versions of the manuscript. DJB was supported by a National Science Foundation Graduate Research Fellowship and ARCS Foundation Award, and RJH was supported by the James S. McDonnell Foundation grant 220020193 and the National Science Foundation grant DEB-1518611.
- Fahrig L (2003) Effects of habitat fragmentation on biodiversity. Annu Rev Ecol Evol Syst 487–515Google Scholar
- Galbraith JA, Beggs JR, Jones DN, Stanley MC (2015) Supplementary feeding restructures urban bird communities. Proc Natl Acad Sci 201501489. doi: 10.1073/pnas.1501489112
- Levins R (1969) Some demographic and genetic consequences of environmental heterogeneity for biological control. Bull ESA 15:237–240Google Scholar
- Pulliam HR (1988) Sources, sinks, and population regulation. Am Nat 652–661Google Scholar
- R Core Team (2013) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, AustriaGoogle Scholar
- Soetaert KER, Petzoldt T, Setzer RW (2010) Solving differential equations in R: package deSolveGoogle Scholar