The role of individual differences in the formation of triadic dominance orders of male green swordtail fish (Xiphophorus helleri)

Triads of Xiphophorus helleri males composed of a large prior winner (A), a small prior winner (alpha), and a small prior loser (omega) were formed. In one condition, A was used as bystander while in another condition it was the small omega. The bystander could see through a transparent partition and observe conflict settlement between the two other fish without interacting with them. As soon as a dominance relationship clearly emerged, the partition was raised and the fish on standby could establish dominance relationships with them. The most frequent triadic structures obtained were A > alpha > omega and A > omega > alpha, indicating that individual characteristics played a determinant role in hierarchy formation. Patterns of assembly depended on individual differences of the fish. The fact that the same dominance structures were reached through various patterns of assembly suggests that individual differences are more determinant than paths of resolution in Xiphophorus.