Multivariate social strategies buffer the fitness consequences of phenotype–environment mismatches

Corné de Groot , Rori Efrain Wijnhorst , Yimen G Araya-Ajoy, Alastair J. Wilson, Henrik Jensen, Jonathan Wright, Niels J. Dingemanse

How organisms adapt to environmental change is a fundamental question in biology. Environmental shifts frequently induce mismatches between an organism's phenotype and its surroundings, including the social environments created by interacting individuals. Such mismatches can be mitigated by modifying one's own phenotype through plasticity, adjusting the environment, or selecting environments matching intrinsic phenotypes. Using a wild passerine bird model, we investigated social foraging under negative frequency-dependent selection, where fitness is determined by the proportion of individuals searching for food (“producing”) versus exploiting others (“scrounging”). Because individuals possess distinct and repeatable behavioral types, they experience unique phenotype–environment mismatches relative to this landscape. By experimentally manipulating group compositions, we estimated how house sparrows integrate plasticity and environmental modification to mitigate these mismatches. We show that individuals adjusted their own foraging tactics while simultaneously eliciting behavioral changes in partners. These responses varied among individuals and are integrated with behavioral types, but their combined effect on phenotypic expression did not shift the population toward the fitness peak, which was already closely approximated by the population mean. Instead, this multivariate strategy attenuated the fitness consequences of phenotype–environment mismatches by redistributing fitness among individuals: those furthest from the peak gain fitness, whereas those closest to it lose fitness. Consequently, social responsiveness and social impact reduced among-individual variation in fitness by 47%, weakening the selective differences that would otherwise drive evolutionary change. Broadly, our findings reveal how coordinated responses to social environments can stabilize individual fitness outcomes while constraining the evolutionary consequences of behavioral variation.