Male–male competition leads to less abundant but more attractive sperm

Abstract

Males employ complex strategies to optimize their reproductive success when faced with male-male competition; for instance, they can adjust the ejaculate characteristics. In copulating species, a male may also strategically adjust his ejaculate expenditure according to female quality. Quantifying the relative contribution of ejaculate plasticity in male reproductive success is often difficult, especially when females exert postcopulatory cryptic choice. One way to quantify the functional significance of ejaculate plasticity is offered by mating systems in which the reproductive partners do not meet each other during insemination. In the collembolan Orchesella cincta, males deposit their ejaculates (spermatophores) irrespective of the presence of females. We tested whether Orchesella males adjust spermatophore number when exposed to the presence of another male and whether changes in spermatophore production influence female choice. We found that Orchesella males display plasticity in spermatophore allocation. Males decreased the spermatophore number when exposed to a rival male. Moreover, females preferentially took up spermatophores of males that were exposed to a competitor. The reduction in spermatophore number suggests, besides an adaptive response to the risk of ejaculate removal by rival males, an optimization strategy owing to the costs of more attractive spermatophores.

Rapid shift in thermal resistance between generations through maternal heat exposure

“…This number may appear small compared to the initial sample size, however, due to the alternation of reproductive with non‐reproductive instars, it is likely that only half of the 139 females were in reproductive instar during the mating trials. Moreover, females sometimes reject a spermatophore, even when in a reproductive instar, as shown in several studies on the reproductive behaviour of O. cincta (Gols et al , Zizzari et al , ).…”

Transgenerational effects of nutrition are different for sons and daughters

“…Orchesella is found in the litter layer of forests and under bark and moss on tree trunks where it feeds primarily on algae (Joosse & Testerink, ; Verhoef et al ., ). This soil arthropod is especially suitable for investigating developmental and transgenerational effects of food availability because (1) it has limited dispersal (Timmermans et al ., ), meaning that under natural conditions the great majority of juveniles feed in the same environment as their parents; (2) it has a well‐known reproductive biology (Gols et al ., ; Zizzari et al ., , ); (3) it is regularly exposed to food shortage (Joosse & Testerink, ); thus, by varying a natural diet of this soil arthropod, we investigated an ecologically relevant situation. Moreover, transgenerational effects have been already demonstrated in this species (see e.g.…”

Flirtation reduces males’ fecundity but not longevity

“…In these models, female promiscuity is proposed to determine SCR and SCI levels and precopulatory energetic costs in males. So far, most empirical studies (e.g., Wedell and Cook 1999;Bretman et al 2009;Ingleby et al 2010;Price et al 2012;Bretman et al 2013a;Xu and Wang 2014) have supported while some (e.g., Cook and Gage 1995;Ramm and Stockley 2007;Worthington et al 2013;Zizzari et al 2013) contradicted these predictions.…”

“…; Zizzari et al. ; Xu and Wang ). The second trade‐off predicts that sexual activities shorten male longevity (e.g., Kotiaho and Simmons ; Simmons and Kotiaho ; Hoefler ; Jordan and Brooks ; Papadopoulos et al.…”

“…The ultimate cost of reproduction for males is investment in current reproduction at the expense of future reproduction and longevity (Scharf et al 2013). The first trade-off lies at the foundation of sperm allocation models assuming a limited amount of sperm and time, which should be optimally distributed (e.g., Wedell et al 2002;Parker and Pizzari 2010;Lize et al 2012;Price et al 2012;Zizzari et al 2013;Xu and Wang 2014). The second trade-off predicts that sexual activities shorten male longevity (e.g., Kotiaho and Simmons 2003;Simmons and Kotiaho 2007;Hoefler 2008;Jordan and Brooks 2010;Papadopoulos et al 2010;Wedell 2010;Bretman et al 2013b;Xu and Wang 2014) although male longevity and reproduction may not always be traded off against each other (Janowitz and Fischer 2010).…”