The evolutionary consequences of behavioural plasticity

When environments change and phenotypes become suboptimal, organisms often mitigate the costs of maladaptation with behavioural adjustments. Although this "buffering" of natural selection is widespread, its evolutionary consequences are poorly understood. Here, I use evolutionary simulations to explore how behavioural plasticity shapes the tempo and mode of adaptive evolution. My results indicate that this fast-acting form of plasticity enhances persistence under suboptimal conditions and facilitates the accumulation of genetic variation within populations. Over short timescales, or when opportunities for niche expansion are limited, the combined action of these effects leads to slower evolution of morphology and physiology. Over longer timescales, or when ecological opportunities abound, it can instead lead to a "Goldilocks" pattern, where evolution is fastest in moderately plastic lineages, whose medium buffering capacity enables persistence in suboptimal conditions without severely constraining subsequent optimizing selection. These findings expose key differences in scope and mechanism relative to other forms of phenotypic plasticity and suggest that behavioural plasticity may more broadly influence the evolutionary trajectories of individual lineages. More generally, they help clarify our understanding of how short-term flexibility shapes long-term adaptation and underscore the need to reassess current risk-assessment frameworks that equate slower evolutionary rates with greater vulnerability to environmental change.