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Please use this identifier to cite or link to this item: http://hdl.handle.net/1807/4405

Title: Populations cycles in microtines: the senescence hypothesis
Authors: Boonstra, Rudy
Keywords: microtine cycles
population regulation
sexual maturity
age structure
Issue Date: 1994
Publisher: Chapman and Hall
Citation: Evolutionary Ecology 8:196-219
Abstract: The cause of population cycles in microtines (voles and lemmings) remains an enigma. I propose a new solution to this problem based on a crucial feature of microtine biology, shifts in age structure, that has been ignored until now. Empirical evidence indicates that age structure must shift markedly toward older animals during declines because of three characteristics of the previous peak year: a shortened breeding season, total replacement of the breeding population from peak to decline, and density-dependent social inhibition of maturation of young. Declines become inevitable as populations composed of older animals survive and reproduce poorly because of the effects of senescence, possibly interacting with the experiences of peak density, and I present both theoretical and empirical evidence for this hypothesis. Though a variety of physiological systems deteriorate with aging, I focus on a crucial one - the inability of older animals to effectively maintain homeostasis in the face of environmental challenges because of a progressive deterioration in the endocrine feedback mechanisms involved in the hippocampal-hypothalamic-pituitary-adrenal axis. Microtine populations will not exhibit cycles where age structure shifts are prevented owing to extrinsic factors such as intense predation. Five testable predictions are made that can falsify this hypothesis.
URI: http://hdl.handle.net/1807/4405
Appears in Collections:Biology

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