Female remating and the intensity of female choice in black-horned tree crickets, Oecanthus nigricornis

Abstract

Repeated mating by females of many species occurs at frequencies in excess of those needed to acquire additional sperm for fertilizing ova. I tested three alternative hypotheses for the rate of remating by females of the courtship-feeding tree cricket, Oecanthus nigricornis Walker, by manipulating diet quality and courtship feeding and measuring the time to remating by the female in relation to four aspects of male phenotype (age, condition, fluctuating asymmetry, and size). First, in courtship-feeding species, remating may be due to selection to increase the amount of nutritional resources provided by males, with nutrient-deprived females remating more quickly. Second, remating may function as a mechanism of postcopulatory mate choice, with females remating quickly when the quality of a previous mate is low. Third, quickness of remating may be the consequence of precopulatory mate choice prior to future matings, with females remating more quickly with high-quality males, regardless of the quality of prior mates. Females on a low-quality diet remated quickly, did not vary remating speed with the phenotype of their first mate, and did not differentially reject prospective second mates with different phenotypes. In contrast, both the degree of coyness (measured as the frequency of mate rejection) and the intensity of female choice (measured as the size differential between accepted and rejected mates) increased with diet quality. These results support both the material-benefits and the precopulatory mate-choice hypotheses for remating speed of female tree crickets. There was mixed support for the postcopulatory choice hypothesis: females on the high-quality diet remated more slowly after first mating with relatively large males, in support of the postcopulatory choice hypothesis; however, the remating interval of females on the high-quality diet decreased with the condition of the first mate, opposite to the prediction of the postcopulatory choice hypothesis.