Adaptations to uncertainty: Asymmetric fitness functions and fluctuating environments

How organisms adapt to unpredictable fluctuations in their environment has long been an intriguing problem in evolutionary biology. Conditions vary over different time scales, producing adaptations against stochasticity both within and between generations. Over evolutionary time, genotypic rather than individual fitness determines these optimal strategies. Adverse fitness effects resulting from maladaptation to unpredictable environmental conditions can be minimized for the individual by insuring against them and by canalizing offspring. Additionally, when the environment varies across generations, bet-hedging (diversifying or conservative) is expected to evolve as a genotypic adaptation to maximize geometric mean fitness, at the cost of arithmetic mean fitness among individuals. Using a simple model with two stochastic survival thresholds for survival, we demonstrate under which patterns of stochasticity these different modes of adaptations can be expected, and clarify how they relate to and interact with each other. Understanding these adaptations can help us predict how organisms may adapt to the unpredictability of anthropogenic climate change.