Why the architecture of environmental fluctuation matters for fitness

Abstract

AbstractThe physical environment provides the very stage upon which the eco-evolutionary play unfolds. How environmental fluctuations affect fitness is thus central to demographic projections, selection predictions, life history analyses, and the conservation of populations. Modelling efforts have mostly dealt with fluctuating environments using stochasticity. However, environmental fluctuations in nature are combinations of non-random components and stochastic noise. For example, some fluctuations contain feedbacks (e.g.disturbances such as floods, fires, and hurricanes), and others are driven by geophysical forces that create fixed cyclicality (e.g.seasonal, tidal, and diel). Here we systematically compare and explain why the ‘architecture’ of fluctuations—both how they are generated in nature and constructed theoretically—influences fitness of structured populations. Fitness is sensitive to the architectures even if they appear indistinguishable in their long-term statistical distributions. Importantly, we highlight two quantitative mechanisms through which fitness depends on fluctuation architecture—consecutiveness of deviations from the environmental mean, and Jensen’s Inequality acting on nonlinear biological parameters—both arguably relevant features in virtually all populations inhabiting variable environments. The fitness divergence we demonstrate and explain is a useful step towards developing evolutionary demographic theory for the prevalent categories of non-random environments.