Intraspecific variation in collective behaviors drives interspecific contests in acorn ants

Intraspecific variation in behavior has largely been neglected by community ecologists to date. Recently, however, a number of studies demonstrated that intraspecific variation can have profound consequences for species interactions and thereby alter community dynamics in solitary organisms. Here, we study how intraspecific variation in collective behaviors (also called "collective personalities") affects the outcome of resource contests between 2 co-occurring species of ants, Temnothorax longispinosus and T. curvispinosus. Our results revealed that intraspecific variation in colonies’ exploration behavior and aggressiveness predicts the outcome of interspecific contests for food and nest sites. How exploratory behavior affected the outcome of the foraging and nest site contests depended on the species: exploratory behavior seemed to enhance performance in foraging contests in T. curvispinosus but diminish it in T. longispinosus. More interestingly, whether a species was successful in nest site contests depended not only on its collective personality but also on the personality of its opponent colony. Temnothorax longispinosus experienced greater success if its opponent colony had similar exploratory tendencies to its own. In contrast, T. curvispinosus performed best when its opponent colony exhibited a contrasting exploratory tendency to its own. Our data demonstrate that intraspecific variation in colony behavior can have consequences for contest outcomes and ensure that no one species or behavioral strategy consistently experiences superior success. This, in turn, might help to maintain variation in collective behavior in multiple interacting populations and prevent competitive exclusion of one of the species.