The Evolution of Agonistic Behavior in Amblyopsid Fishes

Agonistic behavior observed in the Amblyopsidae was analyzed using Brillouin's diversity index. Agonistic behavior was not observed in Chologaster cornuta. Chologaster agassizi and Ambloypsis spelaea, the least cave adapted subterranean species in each subfamilial lineage, engaged in relatively intense, complex agonistic bouts. In contrast, the more highly cave adapted species, Typhlichthys subterraneus and Ambloypsis rosae, engaged in simpler, less intense bouts which were considerably shorter in length. Dominance appeared to be size related in C. agassizi and A. spelaea, dependent on prior residency in A. rosae and possibly a combination of size and prior residency in Typhlichthys. Regressive evolution resulting from reduced selective pressures is seen as the most probable explanation for the observed reduction in agonistic behavior.