SMALL MALE MATING ADVANTAGE AND REVERSED SIZE DIMORPHISM IN POECILIIDFISHES

Despite interspecific differences in the absolute efficiency rate of c opulatory thrusting in Poecilia reticulata, Phalloceros caudimaculatus , Heterandria formosa, Girardinus falcatus and Gambusia holbrooki smal l males had a significant advantage. These differences are discussed i n the light of the interspecific differences in morphology and sexual behaviour. The results of the present study offer an alternative expla nation for the pronounced reversed size dimorphism observed in this fa mily of fishes. The greater efficiency of small males in achieving mat ings when females are unreceptive might also explain why genetically s mall males are maintained in natural populations of many poeciliids, i n spite of the large size advantage in both intrasexual competition an d female choice. (C) 1997 The Fisheries Society of the British Isles.