Sammendrag
In order to understand how organisms cope with ongoing changes in environmental variability, different types of adaptations to environmental uncertainty on different time-scales must be considered together. Conservative bet-hedging represents a long-term genotype-level strategy that maximizes lineage geometric mean fitness in stochastic environments by decreasing individual fitness variance, despite also lowering arithmetic mean fitness. Meanwhile, variance-prone (aka risk-prone) strategies produce greater variance in short-term payoffs because this increases expected arithmetic mean fitness if the relationship between payoffs and fitness is accelerating. Here wWe investigated whether selection for such variance-prone strategies are counteracted by selection for bet-hedging that works to adaptively reduce fitness variance, using geometric mean fitness calculations and two evolutionary simulation models. We predict that variance-prone strategies will be favored in scenarios with more decision events per lifetime and when fitness accumulates additively rather than multiplicatively. In line with this, variance-proneness evolved in fine-grained environments (with lower correlations among individuals in energetic state and/or in payoffs when choosing the variable decision), and with larger numbers of independent decision events over which resources accumulate prior to selection. In contrast, geometric fitness accumulation caused by coarser environmental grain and fewer decision events prior to selection favors conservative bet-hedging via greater variance-aversion. These results advance our understanding of how bet-hedging and variance-sensitive strategies interact to affect decisions related to optimal foraging, migration, life histories and cooperative breeding. By linking disparate fields of research studying adaptations to variable environments we should be more able to understand population and evolutionary responses to human-induced rapid environmental change.
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