Abstract
Male costs of mating are now thought to be widespread. The two-spot ladybird beetle (Adalia bipunctata) has been the focus of many studies of mating and sexual selection, yet the costs of mating for males are unknown. The mating system of A. bipunctata involves a spermatophore nuptial gift ingested by females after copulation. In this study, we investigate the cost to males of mating and of transferring spermatophores in terms of lifespan, ejaculate production and depletion of nutritional reserves. We found that males faced a strong trade-off between mating and survival, with males that were randomly assigned to mate a single time experiencing a 53% reduction in post-mating lifespan compared to non-mating males. This is among the most severe survival costs of a single mating yet reported. However, spermatophore transfer did not impact male survival. Instead, the costs associated with spermatophores appeared as a reduced ability to transfer spermatophores in successive matings. Furthermore, males ingested more food following spermatophore transfer than after matings without spermatophores, suggesting that spermatophore transfer depletes male nutritional reserves. This is to our knowledge the first report of an effect of variation in copulatory behaviour on male foraging behaviour. Overall, our study highlights the advantages of assessing mating costs using multiple currencies, and suggests that male A. bipunctata should exhibit mate choice.
Highlights
The costs of mating for females has long been appreciated [1,2], mating was once thought to be relatively costfree for males
To assess the energetic demands placed on males by spermatophore transfer, we examine how spermatophore transfer relates to male feeding rates after mating, and compare the results to a previous finding that mating has no impact on male food intake [20]
Regardless of spermatophore transfer, had approximately 4-fold greater risk of death compared to non-mated males (Table 1)
Summary
The costs of mating for females has long been appreciated [1,2], mating was once thought to be relatively costfree for males. There is abundant evidence for mating costs for males [3,4,5]. The two-spot ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae) has been widely used to investigate numerous questions in mating behaviour and sexual selection, including female preference [9] and mating resistance [10], polyandry [11], nuptial gifts [12], sexually transmitted disease [13], and sperm competition [14]. The costs of mating for female A. bipunctata have been investigated [15], costs for males are entirely unknown. Male mating costs in other coccinellid beetles are extremely variable, with mating having detrimental, marginal or even positive effects on male lifespan [18,19]
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