Sexual conflict does not maintain female colour polymorphism in a territorial damselfly

Female-limited dimorphism is commonly hypothesized to be an adaptation resulting from male harassment or sexual conflict over female mating rate. We examined whether males discriminate be- tween female colour morphs of the beautiful Hawaiian damselfly, Megalagrion calliphya, in order to evaluate whether male harassment could explain the existence and/or maintenance of this dimorphism. Previous studies of this species suggest that spatially varying ecological selection maintains the dimorphism, but these hypotheses are not mutually exclusive. Here, we used a common method of measuring male behaviour towards secured females at mating sites under naturally occurring conditions, using five populations that range in male-like female morph frequency from 0 to 0.86. We found very low rates of interaction in a total of 64 one-hour trials, and male behaviour towards females did not differ significantly between colour morphs. By comparing the populations that vary in female morph fre- quency, we found no evidence of frequency-dependent sexual selection on colour, suggesting that this polymorphism is maintained by selective forces other than sexual conflict.