Review
When less is more: positive population-level effects of mortality

https://doi.org/10.1016/j.tree.2014.08.006Get rights and content
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Highlights

  • We review the evidence for higher population density under mortality.

  • The positive population-level effects of mortality are life-stage specific and may not be observed in total density.

  • Only theory predicting the life stage specific positive mortality effects accounts for fundamental aspects of individuals.

  • Mortality-induced density increases that are specific to life-history stage are common in nature.

Experimental and theoretical studies show that mortality imposed on a population can counter-intuitively increase the density of a specific life-history stage or total population density. Understanding positive population-level effects of mortality is advancing, illuminating implications for population, community, and applied ecology. Reconciling theory and data, we found that the mathematical models used to study mortality effects vary in the effects predicted and mechanisms proposed. Experiments predominantly demonstrate stage-specific density increases in response to mortality. We argue that the empirical evidence supports theory based on stage-structured population models but not on unstructured models. We conclude that stage-specific positive mortality effects are likely to be common in nature and that accounting for within-population individual variation is essential for developing ecological theory.

Keywords

biomass overcompensation
consumer-resource model
density dependence
fisheries
hydra effect
mortality
numerical response
pest control
population dynamics
population management
predation
size-structure
stage-structure

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