Predictability of Evolution in Fluctuating Environments Despite History-Dependent Fitness Effects

Environmental change is ubiquitous in natural settings, and understanding and predicting the effects of environmental fluctuations remains an open question. Previously, we measured the fitness of S. cerevisiaemutants in static environments and 2-environment fluctuations and showed that fitness in a fluctuating environment can differ drastically from fitness in a static environment, an effect we term “environmental memory”. We found that memory in the components of a fluctuating environment is anti-correlated. Here, we test whether such structure results in predictable evolutionary dynamics. First, we reanalyze data from 2-environment cycles and show that fitness in fluctuating environments is largely predictable from static environments. We infer that the fitness effects of individual environments are generic, separable and additive across 2-environments cycles. We measure the fitness of these mutants in 3-environment cycles, which have two directions (i.e. A-B-C, A-C-B). Consistent with previous findings, mutants differ in fitness in the components of the two directions of the 3-envionment cycle but have similar fitness over the course of the entire cycle. Finally, we evolve strains in both directions of the 3-environment cycles and find that mutants resulting from both cycles are similar in fitness, suggesting that these constraints are significant at an evolutionary timescale. Taken together, our results show that trade-offs in memory constrain evolution in fluctuating environments.