Behaviour 2019
Social rank and species-specific differences influence cooperation and conflict in anemonefish societies 
Theresa Rueger1,2, Siobhan Heatwole3, Marian Y. L. Wong3. 1Boston University, Boston, MA, United States; 2University of Exeter, Penryn, , United Kingdom; 3University of Wollongong, Wollongong, NSW, Australia

In dominance hierarchies, theory suggest that higher ranked individuals should increase aggressions but decrease cooperation. Most empirical tests focus on systems with kin selection. Here we use two anemonefish species with low relatedness within groups (A. percula, A. perideraion) to assess behavioral frequencies for each rank and determine whether behaviours were rank- or size-specific. We found A. perideraion more aggressive and less cooperative than A. percula, likely due to a difference in ecological constraints. We found consistent differences between ranks, with higher ranks more aggressive and more cooperative. Despite low relatedness, we found lower ranked individuals performing cooperative behaviours in both species. When we experimentally promoted rank four individuals, they increased the frequency of aggressive and cooperative behaviours, in line with established rank three individuals. Thus, for the first time, we quantify cooperative behaviours for non-breeding individuals in a marine fish, show that behavioral patterns are rank-specific, and confirm that individuals adjust both aggressive and helping behavior to their expected future fitness.