Sex Differences in “Time Out” from Reproductive Activity and Sexual Selection in Male Bushcrickets (Orthoptera: Zaprochilinae: Kawanaphila mirla)
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Animals of many species prefer some partners over others. Discriminating among potential mates causes strong sexual selection that shapes characters and behaviors. In bushcrickets the sexes shows different latencies to remate due to differences in investment in production of the nuptial gift by males and the induced refractory period in females. We conducted experiments with the Australian bushcricket Kawanaphila mirla to test the variation in male mating success by female choice.
Male remating intervals under unlimited access to food and mates were around two days, whereas most females did not remate within 12 days. Males had therefore a much shorter “time-out” from mating than females. The adult sex ratio from field samples was near to 1:1. Consequently, the OSR was male-biased with more males than females ready to mate. This male-biased OSR led to mating competition in males and choosiness in females. In a field enclosure with unlimited supply of receptive females the number of matings varied widely between males, with twenty percent of males neglected by the females. The number of matings within this enclosure was neither related to male size nor to song characters, recorded previously in the lab. However, the number of matings by individual males was positively correlated to the size of their spermatophore producing accessory gland. Females appear to prefer males with a large nutritive donation, thereby receiving a direct fitness benefit.
KEY WORDS:female choice male-male-competition mating success calling spermatophore nuptial gifts
This study would not have been possible without the help of Winston J. Bailey who invited us to the University of Western Australia, Zoology Department, and provided office and research space during our stay. Brenton Knott generously loaned us camping equipment for the field experiments. We thank Winston J. Bailey and Robert Hickson and three anonymous referees for comments on the manuscript. The research was funded by a postdoctoral grant from the DAAD to GL.
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