Exposing extinction risk analysis to pathogens

Is disease just another form of density dependence?

Leah Gerber, Hamish McCallum, Kevin D. Lafferty, John Sabo, Andy Dobson

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

In the United States and several other countries, the development of population viability analyses (PVA) is a legal requirement of any species survival plan developed for threatened and endangered species. Despite the importance of pathogens in natural populations, little attention has been given to host-pathogen dynamics in PVA. To study the effect of infectious pathogens on extinction risk estimates generated from PVA, we review and synthesize the relevance of host-pathogen dynamics in analyses of extinction risk. We then develop a stochastic, density-dependent host-parasite model to investigate the effects of disease on the persistence of endangered populations. We show that this model converges on a Ricker model of density dependence under a suite of limiting assumptions, including a high probability that epidemics will arrive and occur. Using this modeling framework, we then quantify: (1) dynamic differences between time series generated by disease and Ricker processes with the same parameters; (2) observed probabilities of quasi-extinction for populations exposed to disease or self-limitation; and (3) bias in probabilities of quasi-extinction estimated by density-independent PVAs when populations experience either form of density dependence. Our results suggest two generalities about the relationships among disease, PVA, and the management of endangered species. First, disease more strongly increases variability in host abundance and, thus, the probability of quasi-extinction, than does self-limitation. This result stems from the fact that the effects and the probability of occurrence of disease are both density dependent. Second, estimates of quasi-extinction are more often overly optimistic for populations experiencing disease than for those subject to self-limitation. Thus, although the results of density-independent PVAs may be relatively robust to some particular assumptions about density dependence, they are less robust when endangered populations are known to be susceptible to disease. If potential management actions involve manipulating pathogens, then it may be useful to model disease explicitly.

Original languageEnglish (US)
Pages (from-to)1402-1414
Number of pages13
JournalEcological Applications
Volume15
Issue number4
StatePublished - Aug 2005

Fingerprint

extinction risk
density dependence
pathogen
viability
extinction
endangered species
risk analysis
parasite
persistence
time series

Keywords

  • Density dependence
  • Diffusion approximation
  • Disease
  • Epidemic
  • Epidemiology
  • Extinction risk
  • Host-pathogen interactions
  • Parasite
  • Pathogen
  • Population viability analysis
  • PVA
  • Reservoir host

ASJC Scopus subject areas

  • Ecology

Cite this

Exposing extinction risk analysis to pathogens : Is disease just another form of density dependence? / Gerber, Leah; McCallum, Hamish; Lafferty, Kevin D.; Sabo, John; Dobson, Andy.

In: Ecological Applications, Vol. 15, No. 4, 08.2005, p. 1402-1414.

Research output: Contribution to journalArticle

Gerber, Leah ; McCallum, Hamish ; Lafferty, Kevin D. ; Sabo, John ; Dobson, Andy. / Exposing extinction risk analysis to pathogens : Is disease just another form of density dependence?. In: Ecological Applications. 2005 ; Vol. 15, No. 4. pp. 1402-1414.
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