The evolution of group territoriality: The emergence of sociality in a heterogeneous landscape

Background/Question/Methods   Group territoriality is exhibited in a diverse range of species and is associated with complex behaviors such as cooperation, altruism and warfare. The evolution of this trait and the extent to which the economics of territorial defense alone may drive the evolution of sociality are not well understood. We developed a spatially explicit agent-based simulation model that explored the evolution of group territoriality, patterned after the biology of African lions, well known for their pronounced sociality. Territoriality itself is strongly tied to the structure of a landscape, and the model explored the role of landscape heterogeneity in the evolution of this form of sociality. We also modeled the presence and absence, in all combinations, of three distinct advantages to territorial group formation: cooperative defense, increase in territory size, and territorial inheritance.

Results/Conclusions   Simulation results demonstrated that group territoriality may be an emergent property, which evolves due to the synergistic effects of landscape structure and the presence of behavioral traits that afford advantages in territorial competition. Social individuals were significantly more likely to evolve, within a population of solitary individuals, in heterogeneous landscapes with high-value hotspots and if they exhibited cooperative territorial defense, in particular. The model also showed that group territoriality is more likely to evolve in high density populations and that rates of inter-group conflict are significantly higher in heterogeneous landscapes. These results help us to understand how lions became social as a result of adaptation to the heterogeneous savanna landscape, and also provide insight into the evolution of other group-territorial species, including humans.