Effects of mating history on ejaculate size, fecundity, longevity, and copulation duration in the ant-tended lycaenid butterfly, Jalmenus evagoras |
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Authors: | L Hughes B Siew-Woon Chang D Wagner N E Pierce |
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Institution: | (1) Museum of Comparative Zoology, Harvard University Cambridge, MA 02138, USA, US;(2) Department of Ecology and Evolutionary Biology Princeton University, Princeton, NJ 08544, USA, US |
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Abstract: | The mating system of the Australian lycaenid butterfly, Jalmenus evagoras, is highly unusual compared to most other Lepidoptera. Characteristics of this system, which has been termed an ’explosive
mating strategy,’ include the formation of an intensely competitive mating aggregation of males, a highly male biased operational
sex ratio, a lack of discrimination and mate choice by both sexes, a high variance in male mating success, and female monogamy.
In this study, we tested the hypothesis that multiple mating by males imposes physiological costs resulting in smaller spermatophores,
and that this results in a fitness cost to females. We found that male J. evagoras transferred only 2.2% of their eclosion weight during their first mating, consistent with the hypothesis that males of monandrous
species produce a relatively small investment. The wet weight of the ejaculate declined by an average of 27% at the second
mating and the dry weight by 29%, and an intermating 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 increased proportionally with male size, though dry
mass was proportionally larger 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 positively
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 over 4 h at the third and fourth matings. Fecundity was positively correlated with female size but not with
mating history, copulation duration, or any other characteristics measured for either males or females. Female longevity declined
significantly as the number of times the male partner had previously 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 duration, and reduction in female lifespan with increasing mating number.
Received: 22 January 1999 / Received in revised form: 28 July 1999 / Accepted: 18 September 1999 |
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Keywords: | Copulation duration Explosive mating system Ejaculate size Lepidoptera Mating history |
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