The fitness cost to females of exposure to males does not depend on water availability in seed beetles

Abstract

Access to multiple males can benefit a female because it increases her fecundity and/or the performance of her offspring due to males providing material benefits and/or genetic gains from polyandry (i.e. cryptic female choice). However, the presence of more males can also impose costs on females that arise from an elevated mating rate and/or increased harassment. Understanding how different environments influence the relative magnitude of these costs and benefits is important to understanding how factors that affect the rate of male-female interactions, such as the sex ratio and density of each sex, will alter the evolution of traits due to shifts in the magnitude of sexual conflict and sexual selection. Here we explored whether the net fitness of female seed beetles (Callosobruchus maculatus) is affected by breeding in either a dry or wet environment when housed with differing numbers of males (either none, one or four). Consistent with costly male harassment, females housed with four males laid significantly fewer eggs than those housed alone or with a single male. However, there was no significant effect of the number of males on a female's egg laying rate, her lifespan, larval development rate or the egg-adult survival of offspring. Although females in the wet environment lived significantly longer, the decline in the rate of egg laying and egg-adult survival with maternal age was stronger in the wet than the dry environment. Crucially, there was no evidence that water availability affects the net fitness cost to females of being exposed to more males.

Omnivorous Notoxus trinotatus Pic (Coleoptera: Anthicidae) is a newly recognized vector of northern leaf blight in maize

“…Furthermore, only adults within the water‐fed blank control had a longer survival time compared with feeding on maize tissues. Therefore, beetles also need to supplement a large amount of water to increase their longevity, fitness and reproduction (Iglesias‐Carrasco et al, 2018; Ursprung et al, 2009), and the reason why beetles feeding on maize silk have a longer adult survival time than those feeding on fresh leaves may be related to the greater nutrition and extra water in the silk (Da Silva et al, 2021). This interpretation is consistent with the observation during a sampling survey of beetles on agricultural land that beetles reached their maximum population at the silking stage of maize (hollow the developing), and the number of beetles decreased with the wilting of maize pistillate flowers (the waxy ripe) (Horváth, 2003).…”

Sexual selection, phenotypic plasticity and female reproductive output

“…The most common plastic responses are shifts in sperm production, ejaculate size, and rates of courtship or aggression [63,110 -114]. Studies that examine plastic responses to the social environment by males rarely quantify the effect on female reproductive output ( [115,116]; but see [117]). Instead, researchers usually extrapolate from effects of male traits on females in other studies to predict how male plasticity will alter female LRS.…”

An experimental test for body size‐dependent effects of male harassment and an elevated copulation rate on female lifetime fecundity and offspring performance

“…Many studies have now shown that the greater presence of males (e.g. more male-biased operational sex ratios) is associated with decreased female longevity and/or lower fecundity (Rönn, Katvala, & Arnqvist, 2006;Takahashi & Watanabe, 2010;Iglesias-Carrasco, Bilgin, Jennions, & Head, 2018, but see Head & Brooks, 2006). In general, experimental studies show that females continuously housed with males have lower fitness than females that only have intermittent access to males (Edvardsson, 2007;Lew, Morrow, & Rice, 2006;Rönn et al, 2006).…”