Male antler flies (Protopiophila litigata; Diptera: Piophilidae) are more selective than females in mate choice

Abstract

We investigated mate choice in the antler fly (Protopiophila litigata Bonduriansky), which forms mating aggregations and oviposits exclusively on discarded cervid antlers, by pairing males with nongravid females and by collecting copulating pairs on antlers. Because females probably receive larger ejaculates (which they partly ingest after mating) and more effective protection (mate guarding) from large males than from small ones, we expected females to prefer large males as mates. Because males experience high mating costs and often encounter females lacking mature eggs, we expected males to reject some females. Moreover, because relative abdomen width (fatness) predicts the number of mature eggs (egg load) of a female better than her body size does, we expected males to evaluate female quality by assessing female fatness. Of the 54 male-female pairings, 7 (13%) resulted in copulation, the female rejected the male in 6 (11%), and the male rejected the female in 41 (76%). We found no significant differences between individuals that mated and those that did not. However, females disproportionately rejected males smaller than themselves. Males exhibited a preference (quantified as duration of abdominal tapping bouts) for fat females as mates. Small males appeared to be less choosy than large males. Because males rejected potential mates more frequently than females (apparently) did, males may have been choosier than females. Coupled pairs collected on antlers exhibited positive assortment by body size and positive correlation of male body size with female egg load. These mate-choice and mating-assortment patterns may occur in many dipteran species, where copulation is costly for both sexes, females often lack mature eggs, and mating is initiated in dense aggregations of aggressive males.