Is life-history buffering or lability adaptive in stochastic environments?

International audienceIt is commonly thought that temporal fluctuations in demographic parameters should be selected against because of thedeleterious impacts variation can have on fitness. A critical underpinning of this prediction is the assumption that changesin environmental conditions map linearly into changes in demographic parameters over time. We detail why thisassumption may often break down and why selection should not always favor buffering of demographic parametersagainst environmental stochasticity. To the contrary, nonlinear relationships between the environment and demographicperformance can produce asymmetric temporal variation in demographic parameters that actually enhances fitness. Weextend this result to structured populations using simulation and show that ‘demographic lability’ rather than ‘buffering’may be adaptive, particularly in organisms with low juvenile or adult survival. Finally, we review previous ecologicalwork, and indicate cases where ‘demographic lability’ may be adaptive, then conclude by identifying research that isneeded to develop a theory of life-history evolution that encompasses both demographic buffering and lability