Effects of mating history on ejaculate size, fecundity, longevity, and copulation duration in the ant-tended lycaenid butterfly, Jalmenus evagoras

The mating system of the Australian lycaenid butterfly, Jalmenus evagoras, is highly unusual compared to most other Lepidoptera. Characteristics of th is system, which has been termed an 'explosive mating strategy,' include th e formation of an intensely competitive mating aggregation of males, a high ly male biased operational sex ratio, a lack of discrimination and mate cho ice by both sexes, a high variance in male mating success, and female monog amy. In this study, we tested the hypothesis that multiple mating by males imposes physiological costs resulting in smaller spermatophores, and that t his results in a fitness cost to females. We found that male J. evagoras tr ansferred only 2.2% of their eclosion weight during their first mating, con sistent with the hypothesis that males of monandrous species produce a rela tively small investment. The wet weight of the ejaculate declined by an ave rage of 27% at the second mating and the dry weight by 29%, and an intermat ing interval of 5-9 days was needed for the ejaculate to return to the size at the first mating, regardless of male size or age. Wet ejaculate mass in creased proportionally with male size, though dry mass was proportionally l arger in smaller males. Ejaculate mass tended to increase with male age at both first and second matings. Female characteristics, in general, did not affect ejaculate mass, although the wet weight of the ejaculate was positiv ely associated with female weight at the second mating. Copulation duration increased from 2.4 h to approximately 3 h at the second mating, and to ove r 4 h at the third and fourth matings. Fecundity was positively correlated with female size but not with mating history, copulation duration, or any o ther characteristics measured for either males or females. Female longevity declined significantly as the number of times the male partner had previou sly mated increased. We conclude that despite the small male investment in ejaculate, the costs of multiple mating may nonetheless be significant, as indicated by the reduction in ejaculate mass, an increase in copulation dur ation, and reduction in female lifespan with increasing mating number.