Intralocus sexual conflict and offspring sex ratio

Abstract

Males and females frequently have different fitness optima for shared traits, and as a result, genotypes that are high fitness as males are low fitness as females, and vice versa. When this occurs, biasing of offspring sex-ratio to reduce the production of the lower-fitness sex would be advantageous, so that for example, broods produced by high-fitness females should contain fewer sons. We tested for offspring sex-ratio biasing consistent with these predictions in broad-horned flour beetles. We found that in both wild-type beetles and populations subject to artificial selection for high- and low-fitness males, offspring sex ratios were biased in the predicted direction: low-fitness females produced an excess of sons, whereas high-fitness females produced an excess of daughters. Thus, these beetles are able to adaptively bias sex ratio and recoup indirect fitness benefits of mate choice.

Sexual conflict over mating in Gnatocerus cornutus ? Females prefer lovers not fighters

“…This protocol ensures that the emerging adults do not interact with conspecifics. As G. cornutus males can take up to 7 days to attain sexual maturity ( [45] and see [36]), we allowed individuals from both sexes to mature for 14 days before being used in experiments. All experiments within this study follow this maintenance protocol, unless stated otherwise.…”

“…Lifetime reproductive success (LRS) of each female was scored as the total number of adult offspring emerging from these vials. This provides a good proxy for female LRS (see [36,45,59]), and such proxies of LRS have been used to good effect in other studies [60]. Females were then moved into new vials (40 mm high, 15 mm diameter) containing an excess of the culture medium (4 g) and assessed for survival weekly until death.…”

“…This can occur when males and females express shared traits that are regulated by the same genes, but optimal trait values differ between the sexes [33,34]. This means the genes that make good males do not always make good females, generating negative sire -daughter (and dam-son) fitness associations and indirect fitness costs [35], although these can be reduced by offspring sex-ratio adjustment [36]. Again, evidence consistent with sexually antagonistic selection on shared traits is widespread [37][38][39][40], which seems to restrict the likelihood and/or magnitude of good genes benefits of sexual selection.…”

Sperm speed is associated with sex bias of siblings in a human population

“…In certain environmental conditions, it may be beneficial to produce mainly males and in alternative environments it may be beneficial to produce mainly females, 3 causing sexual antagonism for offspring gender. The ability of mammalian mothers to adjust the sex ratio of their offspring is poorly understood although empirical and theoretical studies in other species have shown that: (i) it is possible; 4 and (ii) it is adaptive. 2 Little is known, however, whether humans are able to manipulate the sex ratio of offspring to maximize their reproductive success and that of their offspring.…”

Sex ratio effects on copulation, fecundity and progeny fitness forAgasicles hygrophila, a biological control agent of alligator weed

“…So far, it is well recognised that many factors, such as LMC (Hamilton, 1967), resource competition (Clark, 1978), maternal quality (Trivers & Willard, 1973), mate attractiveness (Burley, 1981) and variable environment (Charnov, Los-den Hartogh, Jones, & van den Assem, 1981), affect how a mother adjusts her progeny's sex ratios to maximise the fitness returns (House, Simmons, Kotiaho, Tomkins, & Hunt, 2011). Recently, there have been several empirical studies on the sex allocation of beetles examining the above factors (Cruickshank & Wade, 2012;House et al, 2011;Katsuki, Harano, Miyatake, Okada, & Hosken, 2012;Keller, Peer, Bernasconi, Taborsky, & Shuker, 2011;Figure 2. Percentage of female progeny (a) and the rate of population increase (b) for A. hygrophila under different adult sex ratios.…”