Disease in Metapopulation Models: Implications for Conservation

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract.Several conservation measures are intended to enhance the movement of individuals among populations. These include the establishment of wildlife corridors, captive breeding and release programs, and translocation of individuals among populations. Many metapopulation models show that increasing movement among populations reduces the chance of metapopulation extinction. However, epidemiological models indicate that increased contact among populations enhances the spread of disease and can trigger epidemics. I have synthesized elements of mathematical epidemiology with metapopulation models. An analytic model showed that highly contagious diseases of moderate severity spread widely, increasing the probability of metapopulation extinction. I also used a simulation model to examine four spatial arrangements of populations: island, necklace, loop, and spider. When infected individuals were allowed to move freely among populations, all of the arrangements exhibited qualitative behavior similar to that exhibited by the analytic models. The most dangerous diseases were those for which infected populations grew large enough to produce dispersers that infected other populations, but which also reduced the geometric rate of increase for infected populations to near unity. Under those conditions, random demographic and environmental events caused metapopulation extinction. Major differences among the spatial arrangements emerged when a quarantine population was established. A centralized quarantine in the spider and necklace arrangement yielded the most dramatic reductions in metapopulation extinction probability. A single quarantine patch was of little value in an island arrangement. These results have several implications for managing metapopulations. Most notably, some spatial arrangements of populations are more amenable to disease control than others, and establishing a quarantine population can increase the probability of detecting new diseases and reduce the impact of diseases that do appear.

An agent‐based movement model to assess the impact of landscape fragmentation on disease transmission

“…Fragmentation often occurs as a result of habitat removal, but can result from other landscape changes, such as the construction of fences or other features that restrict animal movement. In turn, habitat fragmentation and restricted landscape connectivity can alter interand intra-specific interactions and the potential of disease spread (Hess 1996, McCallum and Dobson 2002, McCallum and Dobson 2006. In many regions, urbanization is a leading cause of habitat fragmentation and species endangerment (McKinney 2002, McDonald et al 2008.…”

“…The effects of habitat fragmentation on pathogen dynamics have been explored theoretically (Hess 1996, McCallum and Dobson 2002, 2006, with differing predictions. A highly fragmented landscape has been shown to reduce betweenpatch transmission by preventing dispersal between habitat patches (Hess 1996).…”

“…A highly fragmented landscape has been shown to reduce betweenpatch transmission by preventing dispersal between habitat patches (Hess 1996). Habitat fragmentation could also limit within-patch transmission by restricting population numbers to levels below threshold values needed by pathogens to persist (Hess 1996).…”

Chytrid fungus Batrachochytrium dendrobatidis has nonamphibian hosts and releases chemicals that cause pathology in the absence of infection

“…A lthough some pathogens are highly host-specific, those infecting multiple host species can profoundly affect disease dynamics by increasing pathogen persistence, virulence, and movement between host populations (1). Furthermore, when there are multiple hosts for a pathogen, some can serve as reservoir hosts.…”

Focusing Ecological Research for Conservation

“…One concern is that by increasing connectivity, corridors might channel spread of invasive plant and animal species (Hulme et al 2008), and also could serve as pathways for disease transmission (Hess 1996). Pushing knowledge boundaries for the ecology of movement in the context of connectivity is important given that fragmentation is a major driver of extinction, aggravating the impacts of habitat loss especially at low proportion of available habitats (Swift and Hannon 2010).…”