Abstract
Male reproductive success in the lesser wax moth Achroia grisella is strongly determined by pre-copulatory mate choice, during which females choose among males aggregated in small leks based on the attractiveness of ultrasonic songs. Nothing is known about the potential of post-copulatory mechanisms to affect male reproductive success. However, there is evidence that females at least occasionally remate with a second male and that males are unable to produce ejaculates quickly after a previous copulation. Here we investigated the effects of mating history on ejaculate size and demonstrate that the number of transferred sperm significantly decreased from first (i.e., virgin) to second (i.e., nonvirgin) copulation within individual males. For males of identical age, the number of sperm transferred was higher in virgin than in nonvirgin copulations, too, demonstrating that mating history, is responsible for the decrease in sperm numbers transferred and not the concomitant age difference. Furthermore, the number of transferred sperm was significantly repeatable within males. The demonstrated variation in ejaculate size both between subsequent copulations as well as among individuals suggests that there is allocation of a possibly limited amount of sperm. Because female fecundity is not limited by sperm availability in this system, post-copulatory mechanisms, in particular sperm competition, may play a previously underappreciated role in the lesser wax moth mating system.
Highlights
Sexual selection, which is responsible for the evolution of many male reproductive characters (Andersson 1994), can be separated into two major components
Male reproductive success in the lesser wax moth Achroia grisella is strongly determined by pre-copulatory mate choice, during which females choose among males aggregated in small leks based on the attractiveness of ultrasonic songs
We have demonstrated that the amount of eupyrene sperm transferred by male lesser wax moths during copu
Summary
Sexual selection, which is responsible for the evolution of many male reproductive characters (Andersson 1994), can be separated into two major components. Male reproductive success will be affected by both processes (Andersson and Simmons 2006) and the precise relationship between these episodes of sexual selection is not yet clear In some species, they are positively correlated and seem to reinforce each other (Lewis and Austad 1994; Bangham et al 2002; Evans et al 2003; Hosken et al 2008) whereas other studies have revealed a negative relationship (Warner et al 1995; Danielsson 2001; Fu et al 2001; Preston et al 2001; Demary and Lewis 2007; Engqvist 2011). More studies addressing sperm competition in species with a well-established pre-copulatory component of sexual selection and vice versa are essential in order to resolve this important evolutionary problem
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