LAUSR

Mismatches between an organism’s phenotype and its environment can result in short-term fitness costs. Here, we show that some phenotype–environment mismatch errors can be explained by asymmetrical costs of different types of errors in wild red squirrels. Mothers that mistakenly increased reproductive effort when signals of an upcoming food pulse were absent were more likely to correctly increase effort when a food pulse did occur. However, mothers that failed to increase effort when cues of an upcoming food pulse were present suffered lifetime fitness costs that could only be offset through food supplementation. In fluctuating environments, such phenotype–environment mismatches may therefore reflect a bias to overestimate environmental cues and avoid making the costliest error, ultimately enhancing lifetime fitness. Description Risky payoffs In nature, environmental fluctuation is common, and some years are good and some are bad for species trying to survive and reproduce. Some animals take bets on what the upcoming environment might be like, and different strategies can affect overall fitness. Petrullo et al. studied different strategies in a population of red squirrels that has been monitored for decades. They found that mother squirrels that bet on a good environment, and produced more offspring, had higher overall fitness than mothers who bet that the environment would be poor. This was the case even when the optimistic mothers were wrong. —SNV In fluctuating environments, phenotypic mismatching may reflect an error-avoidance bias that enhances a mother squirrel’s overall lifetime fitness.