VARIATION OF SPERM PRECEDENCE IN THE ROVE BEETLE ALEOCHARA CURTULA (COLEOPTERA: STAPHYLINIDAE)

We staged eight types of contests using adult male conviet cichlids (Cichlasoma nigrofasciatum) to study the effects of dear enemy recognition on the defensive decisions of territorial residents when confronted by two opponents. Our observations supported the hypothesis that residents faced with two intruders simultaneously would divide the overall response shown to a single intruder between the two intruders with respect to their relative threats (i.e. sizes). Consequently, in comparison to a single-intruder circumstance, the residentsʹ attacks against any given intruder were reduced. The relative threat of competitors was dramatically altered when one of the residentsʹ opponents was a dear enemy neighbour. When faced with a dear enemy neighbour and an unfamiliar intruder simultaneously, residents preferentially confronted the unfamiliar opponent. That is, the establishment of dear enemy recognition between a resident and a neighbour allowed the resident to direct his aggression to the greater competitive threat, i.e. the intruder. In this case. the amount of aggression residents exhibited toward the intruder was similar to the amount of aggression against a single nonterritorial intruder. Therefore, having a dear enemy neighbour freed a resident to defend its territory against an intruder with similar efficiency compared to when the intruder had been the residentʹs only opponent.