Evol Ecol Res 13: 557-569 (2011)     Full PDF if your library subscribes.

Parasites can simplify host-population dynamics and reduce extinction risk

Megan A. Greischar and Curtis M. Lively

Department of Biology, Indiana University, Bloomington, Indiana, USA

Correspondence: M.A. Greischar, Department of Biology, Indiana University, Bloomington, IN 47401, USA.
e-mail: mag450@psu.edu


Question: Can parasites stabilize host-population dynamics and thereby reduce the risk of host extinction?

Model: We analysed a discrete-time model of logistic growth in an annual, asexual host population. Infection was assumed to reduce host fecundity, but not host survival. Using simulations, we determined whether parasites stabilized or destabilized host-population dynamics. We calculated the coefficient of variation and the effective population size (Ne) as measures of host extinction risk.

Ranges of key variables: Per capita birth rates in the host population varied from just above replacement (1.1) to 50. Equilibrium infection prevalence ranged from 0.25% to 99.75%. Infection caused a two- or ten-fold disadvantage in fitness parameters, with the fitness cost being density-independent, density-dependent, or both.

Conclusions: Parasites stabilized host-population dynamics, thereby reducing the coefficient of variation and increasing host Ne, for a broad range of host birth rates. Thus parasites could, in theory, reduce host extinction probabilities in otherwise unstable populations with high intrinsic birth rates.

Keywords: chaos, density dependence, effective population size, extinction, parasite, population regulation.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2011 Megan A. Greischar. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.