Sex differences in nutrient intake can reduce the potential for sexual conflict over fitness maximization by female and male crickets

As females and males have different roles in reproduction, they are expected to require different nutrients for the expression of reproductive traits. However, due to their shared genome, both sexes may be constrained in the regulation of nutrient intake that maximizes sex‐specific fitness. Here, we used the Geometric Framework for nutrition to examine the effect of macronutrient and micronutrient intakes on lifespan, fecundity and cuticular hydrocarbons (CHCs) that signal mate quality to prospective mates in female field crickets, Teleogryllus oceanicus. In addition, we contrasted nutritional effects on life‐history traits between males and females to determine how sex differences influence nutrient regulation. We found that carbohydrate intake maximized female lifespan and protein intake influenced CHC expression, while early life fecundity (cumulative fecundity at day 21) and lifetime fecundity were dependent on both macronutrient and micronutrient intakes. Fecundity required different nutrient blends to those required to optimize sperm viability in males, generating the potential for sexual conflict over macronutrient intake. The regulation of protein (P) and carbohydrate (C) intakes by virgin and mated females initially matched that of males, but females adjusted their intake to a higher P:C ratio, 1P:2C, that maximized fecundity as they aged. This suggests that a sex‐specific, age‐dependent change in intake target for sexually mature females, regardless of their mating status, adjusts protein consumption in preparation for oviposition. Sex differences in the regulation of nutrient intake to optimize critical reproductive traits in female and male T. oceanicus provide an example of how sexual conflict over nutrition can shape differences in foraging between the sexes.     

Little evidence for intralocus sexual conflict over the optimal intake of nutrients for life span and reproduction in the black field cricket Teleogryllus commodus

There is often large divergence in the effects of key nutrients on life span (LS) and reproduction in the sexes, yet nutrient intake is regulated in the same way in males and females given dietary choice. This suggests that the sexes are constrained from feeding to their sex‐specific nutritional optima for these traits. Here, we examine the potential for intralocus sexual conflict (IASC) over optimal protein and carbohydrate intake for LS and reproduction to constrain the evolution of sex‐specific nutrient regulation in the field cricket, Teleogryllus commodus. We show clear sex differences in the effects of protein and carbohydrate intake on LS and reproduction and strong positive genetic correlations between the sexes for the regulated intake of these nutrients. However, the between‐sex additive genetic covariance matrix had very little effect on the predicted evolutionary response of nutrient regulation in the sexes. Thus, IASC appears unlikely to act as an evolutionary constraint on sex‐specific nutrient regulation in T. commodus. This finding is supported by clear sexual dimorphism in the regulated intake of these nutrients under dietary choice. However, nutrient regulation did not coincide with the nutritional optima for LS or reproduction in either sex, suggesting that IASC is not completely resolved in T. commodus.     

Effects of macronutrient intake on the lifespan and fecundity of the marula fruit fly,Ceratitis cosyra (Tephritidae): Extreme lifespan in a host specialist

In insects, lifespan and reproduction are strongly associated with nutrition. The ratio and amount of nutrients individuals consume affect their life expectancy and reproductive investment. The geometric framework (GF) enables us to explore how animals regulate their intake of multiple nutrients simultaneously and determine how these nutrients interact to affect life‐history traits of interest. Studies using the GF on host‐generalist tephritid flies have highlighted trade‐offs between longevity and reproductive effort in females, mediated by the protein‐to‐carbohydrate (P:C) ratio that individuals consume. Here, we tested how P and C intake affect lifespan (LS) in both sexes, and female lifetime (LEP), and daily (DEP) egg production, in Ceratitis cosyra, a host‐specialist tephritid fly. We then determined the P:C ratio that C. cosyra defends when offered a choice of foods. Female LS was optimized at a 0:1 P:C ratio, whereas to maximize their fecundity, females needed to consume a higher P:C ratio (LEP = 1:6 P:C; DEP = 1:2.5 P:C). In males, LS was also optimized at a low P:C ratio of 1:10. However, when given the opportunity to regulate their intake, both sexes actively defended a 1:3 P:C ratio, which is closer to the target for DEP than either LS or LEP. Our results show that female C. cosyra experienced a moderate trade‐off between LS and fecundity. Moreover, the diets that maximized expression of LEP and DEP were of lower P:C ratio than those required for optimal expression of these traits in host‐generalist tephritids or other generalist insects.     

Dietary choice for a balanced nutrient intake increases the mean and reduces the variance in the reproductive performance of male and female cockroaches

Sexual selection may cause dietary requirements for reproduction to diverge across the sexes and promote the evolution of different foraging strategies in males and females. However, our understanding of how the sexes regulate their nutrition and the effects that this has on sex‐specific fitness is limited. We quantified how protein (P) and carbohydrate (C) intakes affect reproductive traits in male (pheromone expression) and female (clutch size and gestation time) cockroaches (Nauphoeta cinerea). We then determined how the sexes regulate their intake of nutrients when restricted to a single diet and when given dietary choice and how this affected expression of these important reproductive traits. Pheromone levels that improve male attractiveness, female clutch size and gestation time all peaked at a high daily intake of P:C in a 1:8 ratio. This is surprising because female insects typically require more P than males to maximize reproduction. The relatively low P requirement of females may reflect the action of cockroach endosymbionts that help recycle stored nitrogen for protein synthesis. When constrained to a single diet, both sexes prioritized regulating their daily intake of P over C, although this prioritization was stronger in females than males. When given the choice between diets, both sexes actively regulated their intake of nutrients at a 1:4.8 P:C ratio. The P:C ratio did not overlap exactly with the intake of nutrients that optimized reproductive trait expression. Despite this, cockroaches of both sexes that were given dietary choice generally improved the mean and reduced the variance in all reproductive traits we measured relative to animals fed a single diet from the diet choice pair. This pattern was not as strong when compared to the single best diet in our geometric array, suggesting that the relationship between nutrient balancing and reproduction is complex in this species.     

Sex-specific fitness effects of nutrient intake on reproduction and lifespan

Diet affects both lifespan and reproduction [1-9], leading to the prediction that the contrasting reproductive strategies of the sexes should result in sex-specific effects of nutrition on fitness and longevity [6, 10] and favor different patterns of nutrient intake in males and females. However, males and females share most of their genome and intralocus sexual conflict may prevent sex-specific diet optimization. We show that both male and female longevity were maximized on a high-carbohydrate low-protein diet in field crickets Teleogryllus commodus, but male and female lifetime reproductive performances were maximized in markedly different parts of the nutrient intake landscape. Given a choice, crickets exhibited sex-specific dietary preference in the direction that increases reproductive performance, but this sexual dimorphism in preference was incomplete, with both sexes displaced from the optimum diet for lifetime reproduction. Sexes are, therefore, constrained in their ability to reach their sex-specific dietary optima by the shared biology of diet choice. Our data suggest that sex-specific selection has thus far failed fully to resolve intralocus sexual conflict over diet optimization. Such conflict may be an important factor linking nutrition and reproduction to lifespan and aging.     

Nutrients, not caloric restriction, extend lifespan in Queensland fruit flies (Bactrocera tryoni)

Caloric restriction (CR) has been widely accepted as a mechanism explaining increased lifespan (LS) in organisms subjected to dietary restriction (DR), but recent studies investigating the role of nutrients have challenged the role of CR in extending longevity. Fuelling this debate is the difficulty in experimentally disentangling CR and nutrient effects due to compensatory feeding (CF) behaviour. We quantified CF by measuring the volume of solution imbibed and determined how calories and nutrients influenced LS and fecundity in unmated females of the Queensland fruit fly, Bactocera tryoni (Diptera: Tephritidae). We restricted flies to one of 28 diets varying in carbohydrate:protein (C:P) ratios and concentrations. On imbalanced diets, flies overcame dietary dilutions, consuming similar caloric intakes for most dilutions. The response surface for LS revealed that increasing C:P ratio while keeping calories constant extended LS, with the maximum LS along C:P ratio of 21:1. In general, LS was reduced as caloric intake decreased. Lifetime egg production was maximized at a C:P ratio of 3:1. When given a choice of separate sucrose and yeast solutions, each at one of five concentrations (yielding 25 choice treatments), flies regulated their nutrient intake to match C:P ratio of 3:1. Our results (i) demonstrate that CF can overcome dietary dilutions; (ii) reveal difficulties with methods presenting fixed amounts of liquid diet; (iii) illustrate the need to measure intake to account for CF in DR studies and (iv) highlight nutrients rather than CR as a dominant influence on LS.     

Macronutrient intake regulates sexual conflict in decorated crickets

Sexual conflict results in a diversity of sex‐specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and free amino acid composition, which influences a female's willingness to fully consume this gift. Complete consumption of this gift maximizes sperm transfer through increased retention of the sperm‐containing ampulla, but hinders post‐copulatory mate choice. Here, we examine the effects of protein (P) and carbohydrate (C) intake on the weight and amino acid composition of the spermatophylax that describes its gustatory appeal to the female, as well as the ability of this gift to regulate sexual conflict via ampulla attachment time. Nutrient intake had similar effects on the expression of these traits with each maximized at a high intake of nutrients with a P : C ratio of 1 : 1.3. Under dietary choice, males actively regulated their nutrient intake but this regulation did not coincide with the peak of the nutritional landscape for any trait. Our results therefore demonstrate that a balanced intake of nutrients is central to regulating sexual conflict in G. sigillatus, but males are constrained from reaching the optima needed to bias the outcome of this conflict in their favour.     

Longevity costs of same‐sex interactions: first evidence from a parasitic wasp

Costs of sexual interactions play a key role in life‐history evolution. Although the costs of reproduction have been investigated in both sexes of many insects, the costs of same‐sex interactions have been examined in few species. In parasitic wasps, very little has been reported about the longevity costs of heterosexual interactions, and nothing is known about longevity costs of same‐sex interactions. In this study, the effects of heterosexual and homosexual activities on longevity were evaluated in Psyttalia concolor (Hymenoptera: Braconidae), a synovigenic koinobiont larval‐pupal endoparasitoid of tephritid flies. When compared with individually housed virgin wasps, male longevity was strongly reduced both in males kept with females, and in males kept with other males. When females were kept with males, their longevity was reduced compared with the virgin females and females kept with other females. Overall, the costs of male–female interactions were considerable in both sexes of P. concolor, while same‐sex activities were found to be costly only among males, suggesting that they may have implications for the evolution of the P. concolor mating system.     

MALE‐BIASED FITNESS EFFECTS OF SPONTANEOUS MUTATIONS IN DROSOPHILA MELANOGASTER

In populations with males and females, sexual selection may often represent a major component of overall selection. Sexual selection could act to eliminate deleterious alleles in concert with other forms of selection, thereby improving the fitness of sexual populations. Alternatively, the divergent reproductive strategies of the sexes could promote the maintenance of sexually antagonistic variation, causing sexual populations to be less fit. The net impact of sexual selection on fitness is not well understood, due in part to limited data on the sex‐specific effects of spontaneous mutations on total fitness. Using a set of mutation accumulation lines of Drosophila melanogaster, we found that mutations were deleterious in both sexes and had larger effects on fitness in males than in females. This pattern is expected to reduce the mutation load of sexual females and promote the maintenance of sexual reproduction.     

Response of the sexes of the subdioecious plant Honckenya peploides to nutrients under different salt spray conditions

Sex dimorphic plants often show sex-specific differences in growth and biomass allocation. These differences have been explained as a consequence of the different reproductive functions performed by the sexes. Such differences may determine the performance of each sex in different habitats and therefore might explain the spatial segregation of the sexes described in many dimorphic plants. We examined the growth, reproductive and physiological responses of the sexes of the subdioecious plant Honckenya peploides to two levels each of salt spray and nutrients, which are assumed to be important selective forces in coastal environments. We found sex-related differences in H. peploides. In particular, females allocated proportionally more dry mass to reproduction and grew less and more slowly than males regardless of salt spray and nutrient conditions, which is interpreted as a trade-off between reproductive and vegetative growth. Regarding physiological response, nutrients significantly increased values of photochemical reflectance index (PRI) in females but not in males, suggesting that photochemical efficiency is more limited by nutrients in females than in males. PRI values also suggest intersexual differences in protection requirements against photoinhibition. The study did not find sex-differential responses to salt spray, which caused a decrease in reproductive effort in both sexes. The sex-related differences in relative growth rates, reproductive allocation and photosynthetic features found here may contribute to explaining habitat-related between-sex differences in performance and, therefore, the spatial segregation of the sexes observed in H. peploides.     

Sex-specific differences in nutrient regulation in a capital breeding caterpillar, Spodoptera litura (Fabricius)

Nutrient requirements by male and female insects are likely to differ, but relatively little is known regarding how sexes differ in their regulation of macronutrient acquisition. The present study reports the results from a laboratory experiment in which behavioural and physiological components of nutrient regulation were compared between male and female caterpillars of Spodoptera litura (Fabricius). When provided with choices between two nutritionally complementary foods (one is a protein-biased diet and the other a carbohydrate-biased diet), both males and females adjusted their food selection to defend an intake target. However, the composition of diet preferred by the two differed, with females selecting significantly more protein than males with no difference in carbohydrate intake between the two. When confined to single diets with varying mixtures of protein and carbohydrate [P:C ratios, expressed as the percentage of diet by dry mass: protein 42%:carbohydrate 0% (p42:c0), p35:c7, p28:c14, p21:c21, p14:c28, p7:c35], females consumed more macronutrients than did males across on all P:C diets except the extremely carbohydrate-biased diet (p7:c35). Under both choice and no-choice feeding condition, such sex differences in nutrient intake were not expressed until late in the feeding stage of the final stadium. Sexes also differed in post-ingestive utilization of ingested nutrients. Females utilized ingested protein for body growth with greater efficiency compared to males, presumably reflecting provisioning their adult needs for protein to develop eggs, whereas males were more efficient at depositing lipids from carbohydrate intake than females.     

Sex differences in insect immune function: a consequence of diet choice?

Males often have reduced immune function compared to females but the proximate mechanisms underlying this taxonomically widespread pattern are unclear. Because immune function is resource-dependent and sexes may have different nutritional requirements, we hypothesized that sexual dimorphism in immune function may arise from differential nutrient intake (acquisition hypothesis). To test this hypothesis, we examined patterns of phenoloxidase (PO) activity in relation to nutrient consumption in Queensland fruit flies (Q-flies). In the first experiment, flies were allowed to choose their preferred nutrient intake. Compared with males, female Q-flies had higher PO activity, consumed more calories, and preferred a higher protein:carbohydrate (P:C) diet, suggesting that differential acquisition could explain sex differences. In the second experiment, we restricted flies to one of 12 diets varying in protein and carbohydrate concentrations and mapped PO activity for each sex onto a nutritional landscape. Counter to our hypothesis, females had higher PO activity than males at any given level of nutrient intake. Both carbohydrate and protein intake affected PO activity in females but only protein affected PO activity in males. Our results indicate that sex differences in Q-fly immune function are not solely explained by sex differences in nutrient intake, although nutrition does contribute to the magnitude of these sex differences.     

Selection on learning performance results in the correlated evolution of sexual dimorphism in life history

The evolution of learning can be constrained by trade‐offs. As male and female life histories often diverge, the relationship between learning and fitness may differ between the sexes. However, because sexes share much of their genome, intersexual genetic correlations can prevent males and females from reaching their sex‐specific optima resulting in intralocus sexual conflict (IaSC). To investigate if IaSC constraints sex‐specific evolution of learning, we selected Caenorhabditis remanei nematode females for increased or decreased olfactory learning performance and measured learning, life span (in mated and virgin worms), reproduction, and locomotory activity in both sexes. Males from downward‐selected female lines had higher locomotory activity and longer virgin life span but sired fewer progeny than males from upward‐selected female lines. In contrast, we found no effect of selection on female reproduction and downward‐selected females showed higher locomotory activity but lived shorter as virgins than upward‐selected females. Strikingly, selection on learning performance led to the reversal of sexual dimorphism in virgin life span. We thus show sex‐specific trade‐offs between learning, reproduction, and life span. Our results support the hypothesis that selection on learning performance can shape the evolution of sexually dimorphic life histories via sex‐specific genetic correlations.     

Costs of reproduction in Nyssa sylvatica: sexual dimorphism in reproductive frequency and nutrient flux

Summary We examined the influence of differential reproductive frequency between the sexes on tertiary (phenotypic) sex ratios in the the dioecious tree Nyssa sylvatica (Nyssaceae). Reproduction was evaluated in relation to sex, size and canopy exposure using flowering data collected from 1229 marked trees over a four year period. For subsets of each population we used data on flower number, fruit crop size, fruit/flower ratios, and individual flower and fruit mass to compare biomass invested in reproductive structures of males and females. We also examined seasonal changes in stem nitrogen and soluble carbohydrate content in relation to flower and fruit production for trees of each sex. Our results indicate that: 1) Male-biased tertiary sex ratios could be explained by more frequent reproduction by male trees; 2) Estimated secondary sex ratios based on sums of all known males and females were not significantly different from 1:1; 3) Flowering frequency of males and females was significantly related to plant size (DBH) and exposure of the canopy to light; 4) Estimtes of reproductive biomass allocation ranged from 1.36 to 10.8 times greater for females relative to males; 5) Flower production was related to stem nutrient status for both sexes, but nutrient depletion and its effect on subsequent flowering was much more pronounced for female trees. We conclude that less frequent flowering by female trees may result from depletion of stored reserves, and that differential flowering frequency in N. sylvatica may ultimately reduce apparent sexual differences in the costs of reproduction.     

Both sexes suffer increased parasitism and reduced energy storage as costs of reproduction in the brown anole,Anolis sagrei

Sexual selection theory proposes that males suffer reduced immune function and increased parasitism as costs of expressing sexual signals. Life‐history theory proposes that females suffer the same costs because of inherent trade‐offs between reproduction and self‐maintenance. Mechanistically, each theory invokes an energetic trade‐off, although few experiments have directly compared these costs of reproduction between the sexes as a result of fundamental sex differences in the nature of reproductive investment and a tendency for each theory to focus on a single sex. To test whether males and females experience comparable costs of reproduction in terms of energetics, immune function, and parasitism, we used gonadectomy to eliminate most aspects of reproductive investment in wild brown anole lizards (Anolis sagrei) of both sexes. We compared these nonreproductive males and females with intact, reproductive controls with respect to stored energy (fat bodies), immune function (swelling response to phytohemagglutinin), and the prevalence and intensity of infection by four types of parasite (gastric nematodes, intestinal nematodes, faecal coccidia, and ectoparasitic mites). Gonadectomized anoles experienced dramatic increases in fat storage that were accompanied by decreases in the prevalence of intestinal nematodes and in the intensity of coccidia infection. These costs of reproduction were comparable between males and females, although neither sex exhibited the predicted increase in immune function after gonadectomy. Our results suggest that, despite fundamental sex differences in the nature of reproductive investment, both male and female anoles experience similar costs of reproduction with respect to energy storage and some aspects of parasitism.     

The complex interplay between macronutrient intake,cuticular hydrocarbon expression and mating success in male decorated crickets

The condition dependence of male sexual traits plays a central role in sexual selection theory. Relatively little, however, is known about the condition dependence of chemical signals used in mate choice and their subsequent effects on male mating success. Furthermore, few studies have isolated the specific nutrients responsible for condition‐dependent variation in male sexual traits. Here, we used nutritional geometry to determine the effect of protein (P) and carbohydrate (C) intake on male cuticular hydrocarbon (CHC) expression and mating success in male decorated crickets (Gryllodes sigillatus). We show that both traits are maximized at a moderate‐to‐high intake of nutrients in a P:C ratio of 1 : 1.5. We also show that female precopulatory mate choice exerts a complex pattern of linear and quadratic sexual selection on this condition‐dependent variation in male CHC expression. Structural equation modelling revealed that although the effect of nutrient intake on mating success is mediated through condition‐dependent CHC expression, it is not exclusively so, suggesting that other traits must also play an important role. Collectively, our results suggest that the complex interplay between nutrient intake, CHC expression and mating success plays an important role in the operation of sexual selection in G. sigillatus.     

Linking larval nutrition to adult reproductive traits in the European corn borer Ostrinia nubilalis

Throughout an organism's lifetime, resources are strategically allocated to many different functions, including reproduction. Reproduction can be costly for both sexes; females produce nutrient‐rich eggs, whereas males of many species produce large and complex ejaculates. In capital breeding insects, nutrients are mainly acquired during the larval period, yet allocation decisions impact the reproductive fitness of adults. The present study examines the effect of larval dietary nitrogen on both male and female reproductive traits in the European corn borer moth Ostrinia nubilalis Hübner, whose adults do not feed and whose males transfer a large, nitrogen‐rich spermatophore. One day post‐eclosion, O. nubilalis adults reared on one of three different diets (3.0%, 1.6%, or 1.1% nitrogen) are mated and two experiments are undertaken: one to measure nitrogen and carbon content of male ejaculates, and the other to determine female fecundity and fertility. Although male larval diet does not alter the percentage nitrogen content of adult somatic tissue, males reared on the higher nitrogen diet (3.0%) produce spermatophores with increased nitrogen relative to somatic nitrogen. Furthermore, females raised on the 3.0% nitrogen diet receive spermatophores with lower carbon : nitrogen ratios and thus more nitrogen. Overall, females lay more eggs as their larval dietary nitrogen increases, although they lay fewer eggs when their mates are raised on the higher (3.0%) nitrogen diet. This suggests that O. nubilalis females may use male‐derived nitrogen not to supplement egg production, but rather for somatic maintenance. Overall, the present study furthers our understanding of how larval diet can affect adult fitness in Lepidoptera.     

Mating experience weakens starvation tolerance in the seed bug Togo hemipterus (Heteroptera: Lygaeidae)

Organisms are exposed to various stresses caused by environmental fluctuations. One of the most common stresses is the shortage of food. Individuals of many species must survive periods of starvation. There appears to be a trade‐off between reproduction and survival. When residual reproductive value declines for an individual, life‐history theory predicts an increase in current reproductive investment. Current reproductive investment differs between virgin and mated individuals. It is likely that mating experience influences starvation tolerance. However, few studies have investigated sex differences in the effect of mating experience on starvation tolerance or clarified the causes of reductions in starvation tolerance in both sexes. In the present study, these questions are investigated using the seed bug Togo hemipterus (Heteroptera: Lygaeidae).The results of the present study demonstrate that mating is costly for both sexes. Mated males show very short survival times and a daily reduction in weight, and daily energy expenditures are significantly greater in mated males than in virgin males. It is possible that starvation increases the mating effort of males, such as behavioural activities and the amount of time spent searching for females. A trade‐off between survival duration and lifetime fecundity is found in virgin females. However, there is no trade‐off in mated females, which have very short survival times. Whether male seminal substances contribute to the short survival times of mated females is considered. This is the first report demonstrating the influence of sex and mating experience on starvation tolerance. Sex‐specific causes for reductions in starvation tolerance are discussed.     

Impacts of diet quality on life‐history and reproductive traits in male and female armed beetle,Gnatocerus cornutus

1. The energy available for reproduction is usually limited by resource acquisition (i.e. condition). Because condition is known to be strongly affected by environmental factors, reproductive investments also vary across heterogeneous environments. 2. Although the condition dependence of reproductive investment is common to both sexes, reproductive traits may exhibit sexually different responses to environmental fluctuation due to sex‐specific life‐history strategies. However, few direct experimental studies have investigated the condition dependence of reproductive investments in both sexes. 3. We investigated the condition dependence of life‐history and reproductive traits of males and females in the beetle Gnatocerus cornutus Fabricus by manipulating larval and adult diet quality. We found that male and female life‐history traits exhibited similar responses to environmental fluctuations. 4. By contrast, the sexes exhibit different patterns of condition dependence in reproductive traits (i.e. the adult nutritional environment has a strong impact on the female lifetime reproductive success, whereas larval nutritional environment strongly affects the secondary sexual trait in males). 5. This difference in the plasticity of reproductive traits may lead to different selection pressures for each sex, even if both sexes develop and/or live in the same environment.     

Sex ratio at mating does not modulate age fitness effects in Drosophila melanogaster

Understanding the effects of male and female age on reproductive success is vital to explain the evolution of life history traits and sex‐specific aging. A general prediction is that pre‐/postmeiotic aging processes will lead to a decline in the pre‐ and postcopulatory abilities of both males and females. However, in as much the sexes have different strategies to optimize their fitness, the decline of reproductive success late in life can be modulated by social context, such as sex ratio, in a sex‐specific manner. In this study, we used Drosophila melanogaster to investigate whether sex ratio at mating modulates age effects on male and female reproductive success. As expected, male and female age caused a decrease in reproductive success across male‐biased and female‐biased social contexts but, contrary to previous findings, social context did not modulate age‐related fitness decline in either of the two sexes. We discuss these results in the light of how sex ratio might modulate pre‐/postcopulatory abilities and the opportunity for inter‐ and intrasexual competition in D. melanogaster, and generally suggest that social context effects on these processes are likely to be species specific.