Range expansion induces variation in a behavioural trait in an ant-plant mutualism

► A plant-ant species showed a more dispersive strategy at colonization front, including a lower relative investment in workers. ► We showed that ants invested less in plant defence behaviour at the colonization front. ► The global ant strategy is thus less mutualistic at colonization front. ► Range expansion can shape ant behavioural traits and potentially the outcome of mutualism.