Fundamental and realised behaviours structure geographic variation in ecological assemblages.

Animal behaviours shape ecological dynamics, from species distributions to ecosystem function. These dynamics emerge from the behaviours of multiple interacting species, which reflect both the available species pool and local environmental conditions. By taking an assemblage-scale approach, we add a new dimension to reveal how and why behaviour varies geographically and with what consequences. We distinguish between fundamental behaviours, a species' full repertoire, and realised behaviours, the filtered subset expressed locally. This framework provides the foundation for understanding geographic variation in assemblage-level behaviours, guiding development of testable predictions about how environmental gradients structure behavioural expression across space, with the potential to identify consequences for ecosystem function and behaviourally mediated vulnerabilities under global change.