PLoS ONE

The Demographic Benefits of Belligerence and Bravery: Defeated Group Repopulation or Victorious Group Size Expansion?



Belligerence increases an actor's group probability of trying to conquer another group and bravery increase the actors's group probability of defeating an attacked group.

first

repopulation of defeated groups by fission of victorious ones

second

temporary increase in the local carrying capacity of victorious groups, after transfer of resources from defeated groups to victorious ones.

selective pressures on belligerence and bravery are stronger when defeated groups can be repopulated by victorious ones.

6(7): e21437. doi:10.1371/journal.pone.0021437Laurent LehmannIntraspecific coalitional aggression between groups of individuals is a widespread trait in the animal world. It occurs in invertebrates and vertebrates, and is prevalent in humans. What are the conditions under which coalitional aggression evolves in natural populations? In this article, I develop a mathematical model delineating conditions where natural selection can favor the coevolution of belligerence and bravery between small-scale societies.The model takes into account two different types of demographic scenarios that may lead to the coevolution of belligerence and bravery. Under the, the fitness benefits driving the coevolution of belligerence and bravery come through the. Under thedemographic scenario, the fitness benefits come through aThe analysis of the model suggests that theThe analysis also suggests that, depending on the shape of the contest success function, costly bravery can evolve in groups of any size.