Short‐term insurance versus long‐term bet‐hedging strategies as adaptations to variable environments

Abstract

Understanding how organisms adapt to environmental variation is a key challenge of biology. Central to this are bet‐hedging strategies that maximize geometric mean fitness across generations, either by being conservative or diversifying phenotypes. Theoretical models have identified environmental variation across generations with multiplicative fitness effects as driving the evolution of bet‐hedging. However, behavioral ecology has revealed adaptive responses to additive fitness effects of environmental variation within lifetimes, either through insurance or risk‐sensitive strategies. Here, we explore whether the effects of adaptive insurance interact with the evolution of bet‐hedging by varying the position and skew of both arithmetic and geometric mean fitness functions. We find that insurance causes the optimal phenotype to shift from the peak to down the less steeply decreasing side of the fitness function, and that conservative bet‐hedging produces an additional shift on top of this, which decreases as adaptive phenotypic variation from diversifying bet‐hedging increases. When diversifying bet‐hedging is not an option, environmental canalization to reduce phenotypic variation is almost always favored, except where the tails of the fitness function are steeply convex and produce a novel risk‐sensitive increase in phenotypic variance akin to diversifying bet‐hedging. Importantly, using skewed fitness functions, we provide the first model that explicitly addresses how conservative and diversifying bet‐hedging strategies might coexist.

Optimal germination timing in unpredictable environments: the importance of dormancy for both among‐ and within‐season variation

“…The variance reduction in bet hedging refers to fitness, not to phenotypes. Reduced fitness variance can be achieved by either large or small phenotypic variances, and the bet hedging literature assigns the labels 'diversifying' and 'conservative' bet hedging to these two options, respectively, although individuals can adopt a combination of these strategies (Haaland et al 2019). Both are relevant when the phenotype is germination timing.…”

Environmental variability and the evolution of bet-hedging strategies

“…To combat environmental uncertainty when fluctuations are unpredictable, populations evolve bet-hedging strategies (Simons 2011), allowing some proportion of individuals to avoid or escape unsuitable conditions (Haaland et al 2019). Across the tree of life, dispersal and dormancy are two common forms of bet hedging.…”

Generalists versus specialists in fluctuating environments: a bet-hedging perspective

“…Environmental fluctuations across different time scales pose a challenge for the evolution of organisms subjected to them, as well as for the researchers studying them (Botero et al 2015;Tufto 2015). Notably, different fields of research have taken very different approaches to studying adaptations to stochastic environments, resulting in somewhat disparate bodies of literature dealing with quite similar topics (see Haaland et al 2019).…”