Is life-history buffering or lability adaptive in stochastic environments?
Abstract
It is commonly thought that temporal fluctuations in demographic parameters should be selected against because of the
deleterious impacts variation can have on fitness. A critical underpinning of this prediction is the assumption that changes
in environmental conditions map linearly into changes in demographic parameters over time. We detail why this
assumption may often break down and why selection should not always favor buffering of demographic parameters
against environmental stochasticity. To the contrary, nonlinear relationships between the environment and demographic
performance can produce asymmetric temporal variation in demographic parameters that actually enhances fitness. We
extend 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 ecological
work, and indicate cases where ‘demographic lability’ may be adaptive, then conclude by identifying research that is
needed to develop a theory of life-history evolution that encompasses both demographic buffering and lability.