Behavior as a keystone trait: a conceptual framework applied to the problem of heat

Rising global temperatures underscore the urgent need to interrogate the longstanding hypothesis that behavioral traits play an influential role in adaptation to environmental change. The past decade has seen major gains in understanding how physiology responds to heat, but key gaps remain regarding the role of diverse behavioral traits. Here, we advance the idea that some behaviors may function as keystone traits, exerting disproportionate and cascading effects on organismal performance, population-level processes, and evolutionary outcomes under heat. In this perspective piece, we urge new research to isolate the role of behavior in mitigating heat via an explicitly behavior-centric framework, which features three key components: First, experiment design must scrutinize the scope, causes, and downstream consequences of behavioral variation. Second, we must expand our conception of what types of behaviors shape performance under heat, moving beyond the current focus on movement and heat dissipation behaviors. Third, we must explicitly integrate behavioral variation across scales to link individual changes in behavior with population level processes. By testing whether, how, and when behavioral traits hold the front line in defense of heat, we sharpen our ability to predict organismal responses to our changing world.