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Coevolutionary arms races between brood parasites and hosts provide tractable systems for understanding antagonistic coevolution in nature; however, little is known about the fate of frontline antiparasite defenses when the host “wins” the coevolutionary arms race. By recreating bygone species interactions, using artificial parasitism experiments, lingering defensive behaviors that evolved in the context of parasitism can be understood and may even be used to identify the unknown agent of parasitism past. Here we present the first study of this type by evaluating lingering “frontline” nest defenses that have evolved to prevent egg laying in a former brood parasite host. The Australian reed warbler Acrocephalus australis is currently not parasitized but is known to exhibit fine-tuned egg discrimination—a defensive behavior indicative of a past brood parasite–host arms race and common in closely related parasitized species. Here, using 3D-printed models of adult brood parasites, we examined whether the Australian reed warbler also exhibits frontline defenses to adult brood parasites, and whether we could use these defenses to identify the warbler’s “ghost of parasitism past.” Our findings provide evidence that the Australian reed warbler readily engages in frontline defenses that are considered adaptive specifically in the context of brood parasitism. However, individuals were unable to discriminate between adults of different brood parasite species at their nest. Overall, our results demonstrate that despite a relaxation in selection, defenses against brood parasitism can be maintained across multiple stages of the host’s nesting cycle, and further suggest that, in accordance with previous findings, that learning may be important for fine-tuning frontline defense.

Sexual traits are subject to evolutionary forces that maximize reproductive benefits and minimize survival costs, both of which can depend on environmental conditions. Latitude explains substantial variation in environmental conditions. However, little is known about the relationship between sexual trait variation and latitude, although body size often correlates with latitude. We examined latitudinal variation in male and female sexual traits in 22 populations of the false blister beetle Oedemera sexualis in the Japanese Archipelago. Males possess massive hind legs that function as a female‐grasping apparatus, while females possess slender hind legs that are used to dislodge mounting males. Morphometric analyses revealed that male and female body size (elytron length), length and width of the hind femur and tibia, and allometric slopes of these four hind leg dimensions differed significantly among populations. Of these, three traits showed latitudinal variation, namely, male hind femur was stouter; female hind tibia was slenderer, and female body was smaller at lower latitudes than at higher latitudes. Hind leg sizes and shapes, as measured by principal component analysis of these four hind leg dimensions in each sex, covaried significantly between sexes, suggesting coevolutionary diversification in sexual traits. Covariation between sexes was weaker when variation in these traits with latitude was removed. These results suggest that coevolutionary diversification between male and female sexual traits is mediated by environmental conditions that vary with latitude.

Host genetic variation plays an important role in the structure and function of heritable microbial communities. Recent studies have shown that insects use immune mechanisms to regulate heritable symbionts. Here we test the hypothesis that variation in symbiont density among hosts is linked to intraspecific differences in the immune response to harboring symbionts. We show that pea aphids (Acyrthosiphon pisum) harboring the bacterial endosymbiont Regiella insecticola (but not all other species of symbionts) downregulate expression of key immune genes. We then functionally link immune expression with symbiont density using RNAi. The pea aphid species complex is comprised of multiple reproductively-isolated host plant-adapted populations. These ‘biotypes’ have distinct patterns of symbiont infections: for example, aphids from the Trifolium biotype are strongly associated with Regiella. Using RNAseq, we compare patterns of gene expression in response to Regiella in aphid genotypes from multiple biotypes, and we show that Trifolium aphids experience no downregulation of immune gene expression while hosting Regiella and harbor symbionts at lower densities. Using F1 hybrids between two biotypes, we find that symbiont density and immune gene expression are both intermediate in hybrids. We propose that in this system, Regiella symbionts are suppressing aphid immune mechanisms to increase their density, but that some hosts have adapted to prevent immune suppression in order to control symbiont numbers. This work therefore suggests that antagonistic coevolution can play a role in host-microbe interactions even when symbionts are transmitted vertically and provide a clear benefit to their hosts. The specific immune mechanisms that we find are downregulated in the presence of Regiella have been previously shown to combat pathogens in aphids, and thus this work also highlights the immune system’s complex dual role in interacting with both beneficial and harmful microbes., Author summary Insects frequently form beneficial partnerships with heritable microbes that are passed from mothers to offspring. Natural populations exhibit a great deal of variation in the frequency of heritable microbes and in the within-host density of these infections. Uncovering the mechanisms underlying variation in host-microbe interactions is key to understanding how they evolve. We study a model host-microbe interaction: the pea aphid and a heritable bacterium that makes aphids resistant to fungal pathogens. We show that aphids harboring bacteria show sharply reduced expression of innate immune system genes, and that this leads to increased densities of symbionts. We further show that populations of aphids that live on different species of plants vary in differential immune gene expression and in the density of their symbiont infections. This study contributes to our mechanistic understanding of an important model of host-microbe symbiosis and suggests that hosts and heritable microbes are evolving antagonistically. This work also sheds light on how invertebrate immune systems evolve to manage the complex task of combatting harmful pathogens while accommodating potentially beneficial microbes.

Coevolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by reestablishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. The TART-A TE functions as an important component of Drosophila telomeres but has also reportedly inserted into the Drosophila melanogaster nuclear export factor gene nxf2. We find that, rather than inserting into nxf2, TART-A has actually captured a portion of nxf2 sequence. We show that TART-A produces abundant Piwi-interacting small RNAs (piRNAs), some of which are antisense to the nxf2 transcript, and that the TART-like region of nxf2 is evolving rapidly. Furthermore, in D. melanogaster, TART-A is present at higher copy numbers, and nxf2 shows reduced expression, compared to the closely related species Drosophila simulans. We propose that capturing nxf2 sequence allowed TART-A to target the nxf2 gene for piRNA-mediated repression and that these 2 elements are engaged in antagonistic coevolution despite the fact that TART-A is serving a critical role for its host genome., Co-evolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by re-establishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. This study shows that a specialized Drosophila retrotransposon that functions as a telomere has captured a portion of a host piRNA gene which may allow it to evade silencing.

Male mating plugs have been used in many species to prevent female re-mating and sperm competition. One of the most extreme examples of a mating plug is the sphragis, which is a large, complex and externalized plug found only in butterflies. This structure is found in many species in the genus Acraea (Nymphalidae) and provides an opportunity for investigation of the effects of the sphragis on the morphology of the genitalia, which is poorly understood. This study aims to understand morphological interspecific variation in the genitalia of Acraea butterflies. Using specimens from museum collections, abdomen dissections were conducted on 19 species of Acraea: 9 sphragis bearing and 10 non-sphragis bearing species. Genitalia imaging was performed for easier comparison and analysis and measurements of genitalia structures was done using ImageJ software. Some distinguishing morphological features in the females were found. The most obvious difference is the larger and more externalized copulatory opening in sphragis bearing species, with varying degrees of external projections. Females of the sphragis bearing species also tend to have a shorter ductus (the structure that connects the copulatory opening with the sperm storage organ) than those without the sphragis. These differences may be due to a sexually antagonistic coevolution between the males and females, where the females evolve larger and more difficult to plug copulatory openings and the males attempt to prevent re-mating with the sphragis.

We revise the Oriental species of Bruchomyiinae based on type and additional material, with first descriptions of the genus Alexanderia Wagner & Kvifte, gen. nov. and A. thailandensis Wagner, Rulik & Polseela, sp.nov. The genus further comprises Nemapalpus orientalis Edwards, 1928 (type species), Nemopalpus vietnamensis Quate, 1962 and Nemapalpus unicolor Edwards, 1928. Alexanderia thailandensis is described using morphology of males and females and DNA barcodes, whereas A. orientalis Edwards, 1928 comb.nov., A. unicolor Edwards 1928 comb.nov., and A. vietnamensis Quate 1962 comb. nov. are redescribed. The male and female internal genitalia in the genus are discussed in the context of sexual selection, and we suggest that the spermathecal ducts of the female and the basiphallic musculature of the male may be shaped by a male/female coevolutionary arms race.

Avoiding water loss for insects is critical for survival. Selection for reduced water loss will depend on trade-offs between resources allocated for reproduction and those allocated for resisting desiccation. However, we lack knowledge on how selection for desiccation resistance can affect the male ejaculate. Furthermore, as male ejaculate composition is complex, desiccation resistant females could evolve traits that enable them to derive longevity benefits from mating. Here, we assessed how selection for desiccation resistance impacts male testes and accessory gland size, protein content of these organs, female sperm storage and male ability to inhibit female remating behavior, in the Mexican fruit fly Anastrepha ludens. Additionally, we tested if mating increased longevity and fecundity in desiccation resistant females. Males selected for resistance to desiccation stress had smaller accessory glands and seminal vesicles and females mating with these males stored less sperm compared to control males. Females mating with resistant males had lower fecundity compared to females mating with control males. Desiccation resistant females lived longer than control females, yet this was irrespective of mating. Rapid evolutionary responses to hydric stress can have correlated effects in reproductive capabilities, which are not restricted to pre-copulatory traits. Trade-offs between resistance to desiccation stress are reflected in decreased allocation of resources to reproductive organs. Thus, production of the ejaculate may be costly for A. ludens males. Knowledge on the evolution of ejaculate traits and reproductive organ size in response to directional selection for desiccation resistance, will aid our understanding of differential sex-specific responses to environmental stress.

Parasite virulence is a key trait in host-parasite interactions and plays a crucial role in infection dynamics. Our study system offers the rare opportunity to study the virulence of an individual macroparasite (Schistocephalus solidus) in its vertebrate fish host (Gasterosteus aculeatus). The size of the tapeworm in the fish can be regarded as a good proxy for individual parasite virulence, as parasite size correlates negatively with fitness traits of the stickleback host (i.e. the bigger the parasite, the lower the host's reproductive success) as well as directly with the number of parasite offspring to be expected. To investigate how virulence is inherited, laboratory bred, parasite-naïve stickleback were infected with a cross of two S. solidus populations of either high or low virulence, as well as one hybrid cross between the two. The relative weight of the parasite as expressed in the parasite index served as a measure of virulence. Furthermore, we measured several condition and immune related traits in the fish host to assess parasite impact on the stickleback. We hypothesized that parasite virulence is to a large extent genetically determined and correlated with several fitness traits in the stickleback host. We found that virulence is inherited additively in S. solidus, with hybrids of high and low virulence parasites displaying intermediate levels. However, contrary to expectation, infection rate of S. solidus in three-spined stickleback is not related to virulence. Even though the presence of the parasite caused differences in host condition, these were indistinguishable between the different levels of virulence in this experiment. Fish immune traits also showed a response to infection but had no correlation with level of parasite virulence. With this experiment we have taken the first step towards understanding how virulence is inherited and how it is driven in the Schistocephalus-stickleback system, even though virulence, as measured here, does not directly translate into cost for the host. A better understanding of the costs inflicted on the host by S. solidus infection is needed to understand this interaction in greater detail.

All too often, studies of sexual selection focus exclusively on the responses in one sex, on single traits, typically those that are exaggerated and strongly sexually dimorphic. They ignore a range of less obvious traits and behavior, in both sexes, involved in the interactions leading to mate choice. To remedy this imbalance, we analyze a textbook example of sexual selection in the stalk‐eyed fly (Diasemopsis meigenii). We studied several traits in a novel, insightful, and efficient experimental design, examining 2,400 male–female pairs in a “round‐robin” array, where each female was tested against multiple males and vice versa. In D. meigenii, females exhibit strong mate preference for males with highly exaggerated eyespan, and so we deliberately constrained variation in male eyespan to reveal the importance of other traits. Males performing more precopulatory behavior were more likely to attempt to mate with females and be accepted by them. However, behavior was not a necessary part of courtship, as it was absent from over almost half the interactions. Males with larger reproductive organs (testes and accessory glands) did not make more mating attempts, but there was a strong tendency for females to accept mating attempts from such males. How females detect differences in male reproductive organ size remains unclear. In addition, females with larger eyespan, an indicator of size and fecundity, attracted more mating attempts from males, but this trait did not alter female acceptance. Genetic variation among males had a strong influence on male mating attempts and female acceptance, both via the traits we studied and other unmeasured attributes. These findings demonstrate the importance of assaying multiple traits in males and females, rather than focusing solely on prominent and exaggerated sexually dimorphic traits. The approach allows a more complete understanding of the complex mating decisions made by both males and females.

Male ejaculates in insects include a complex array of substances other than sperm whose proximate functions have proven to be diverse. Some function as allohormones that manipulate post-mating female physiology and behaviour. As each sex pursues their own reproductive interests to maximise fitness, seminal allohormones are expected to promote outcomes ranging from reproductive cooperation to sexual conflict and antagonistic coevolution. Most research on the evolutionary importance of male seminal donations has targeted highly polyandrous species, and more research is needed on usually monandrous species. Here, we explore in the mostly monandrous moth Lobesia botrana if there is variation among males in their ability to influence female post-mating receptivity (PMR), if the trait covariates with the polyandry level of the parental strain and if it could be mediated by ejaculate composition when taking into account spermatophore size. To do this, we conducted controlled reciprocal crosses between field-collected mostly monandrous strains and laboratory-selected highly polyandrous strains. We found that laboratory strain males were significantly less efficient than field strain males at inhibiting female PMR, and that such variation covariate with the polyandry level of the parental strain. Male strain also influenced the duration of the female refractory period, fecundity and fertility being high and roughly similar. Between-strain differences in the ability of males to influence female PMR suggest an effect of seminal fluid composition and its underlying genetic variation in male strains. Further research is needed to assess whether male donations that regulate female PMR are widespread in monandrous insect species to better understand the wider evolutionary significance of these findings in L. botrana. The available evidence suggests that male-donated allohormonal substances (including parasperm) can influence/manipulate female PMR in insects. Most research on this issue has targeted polyandrous species, as it is often implicitly assumed that in monandrous species eupyrene sperm itself plays the key role in inhibiting female PMR. We studied whether male donations could have some allohormonal effect on female PMR in the usually monandrous moth Lobesia botrana. Controlled crosses between field-collected mostly monandrous strains and artificially selected highly polyandrous strains suggest that there is genetic variation in ejaculate composition-mediated male ability to influence/manipulate female PMR.

Conflicts of interests between males and females over reproduction is a universal feature of sexually reproducing organisms and has driven the evolution of intersexual mimicry, mating behaviours and reproductive polymorphisms. Here, we show how temperature drives pre-reproductive selection in a female colour polymorphic insect that is subject to strong sexual conflict. These species have three female colour morphs, one of which is a male mimic. This polymorphism is maintained by frequency-dependent sexual conflict caused by male mating harassment. The frequency of female morphs varies geographically, with higher frequency of the male mimic at higher latitudes. We show that differential temperature sensitivity of the female morphs and faster sexual maturation of the male mimic increases the frequency of this morph in the north. These results suggest that sexual conflict during the adult stage is shaped by abiotic factors and frequency-independent pre-reproductive selection that operate earlier during ontogeny of these female morphs.

Evolutionary conflicts are pervasive in nature and have the potential to drive antagonistic coevolution of conflict-related traits. However, when such conflicts are weak or idiosyncratic, phenotypic signatures of coevolutionary arms races may be absent. Here, we ask whether variation in group-living traits among pine-sawfly species in the genus Neodiprion is consistent with a history of parent-offspring conflict. To address this question, we compile data on adult female clutch size, larval aggregation behavior, and larval group size for a monophyletic group of 19 eastern North American Neodiprion species from field observations, laboratory assays, and published descriptions. We then evaluate the extent to which each trait exhibits phylogenetic signal and, based on these results, examine correlations between group-size traits both with and without phylogenetic correction. Although female oviposition behavior and larval grouping behavior varies among species and variation in these traits is decoupled from phylogeny, we find no evidence of antagonistic coevolution between these traits. Furthermore, while larvae are physically capable of dispersal, female clutch size is a strong predictor of larval colony size, indicating that larvae do not substantially alter initial group size after hatching. Thus, although theoretical work demonstrates the potential for parent-offspring conflict over group size in animals that lack parental care, our data suggest that this type of conflict is not likely to be a long-term driver of phenotypic evolution.

Sexually antagonistic coevolution can drive the evolution of male traits that harm females, and female resistance to those traits. While males have been found to vary their harmfulness to females in response to social cues, plasticity in female resistance traits remains to be examined. Here, we ask whether female seed beetles Callosobruchus maculatus are capable of adjusting their resistance to male harm in response to the social environment. Among seed beetles, male genital spines harm females during copulation and females might resist male harm via thickening of the reproductive tract walls. We develop a novel micro computed tomography imaging technique to quantify female reproductive tract thickness in three-dimensional space, and compared the reproductive tracts of females from populations that had evolved under high and low levels of sexual conflict, and for females reared under a social environment that predicted either high or low levels of sexual conflict. We find little evidence to suggest that females can adjust the thickness of their reproductive tracts in response to the social environment. Neither did evolutionary history affect reproductive tract thickness. Nevertheless, our novel methodology was capable of quantifying fine-scale differences in the internal reproductive tracts of individual females, and will allow future investigations into the internal organs of insects and other animals.

In mating systems with strictly limited male mating opportunities, a male's reproductive success depends strongly on the quality of his mate. Female quality is often linked to body size and mass. Hence, males with limited mating opportunities should choose large and heavy females to maximize their reproductive success. However, high-quality females are likely to attract more than one male, which consequently results in male–male competition. This scenario can be found in the spider species Argiope lobata. Males can copulate twice at most and eventually die after mating, but can monopolize females through the application of mating plugs. These plugs are costly because males block the female's genital openings with parts of their sperm-transferring organs (pedipalps), rendering them dysfunctional. Plugging moreover increases the risk of sexual cannibalism. We tested whether male A. lobata adjust their mating investment to the expected gains, which are a function of female fecundity and the risk of sperm competition. We presented males with virgin females of different fecundity, in either the presence or absence of a rival. Indeed, we found that males were selective and preferred larger females under competitive conditions. When a rival was present and the female was small, males frequently performed ultrashort copulations of less than 3 s without sperm transfer. Ultrashort copulations may imply that males were not willing to invest in paternity under these conditions. In contrast, when two rivals competed for heavy and thus fecund females, males were significantly more likely to monopolize paternity by depositing a plug. In conclusion, our results suggest that males try to adapt their copulatory behaviour to female quality and the degree of sperm competition even in ‘dangerous’ mating systems.

The reversal of conventional sex roles was enigmatic to Darwin, who suggested that it may evolve when sex ratios are female biased [1]. Here we present direct evidence confirming Darwin's hypothesis. We investigated mating system evolution in a sex-role-reversed beetle (Megabruchidius dorsalis) using experimental evolution under manipulated sex ratios and food regimes. In female-biased populations, where reproductive competition among females was intensified, females evolved to be more attractive and the sex roles became more reversed. Interestingly, female-specific mating behavior evolved more rapidly than male-specific mating behavior. We show that sexual selection due to reproductive competition can be strong in females and can target much the same traits as in males of species with conventional mating systems. Our study highlights two central points: the role of ecology in directing sexual selection and the role that females play in mating system evolution.

The mechanisms driving the coevolution of male and female genital morphologies are still debated. Female genitalia in Drosophila species bear membranous "pouches" or hardened "shields," which the male genital armature contact during copulation. Although shield-like structures likely serve to mitigate the effects of harmful mating, some authors have suggested that soft pouches, which do not prevent male genitalia from inflicting wounds, represent a congruent sensory organ. To elucidate the evolutionary forces responsible for the development of such organs, I examined the effects of artificial damage to various genital parts of female Drosophila erecta on reproductive success. Despite a high survival rate among females, damage to the ovipositor plate resulted in frequent failure of insemination and in the embedment of eggs into the substrate. Damage to the vaginal shield resulted in increased mortality and frequent failure of egg embedment, with an egg blocking the vagina under the damaged shield in some females. Wounding of the pouch had less of an effect on both mating and oviposition success, suggesting that the structure "lures" the male trauma-causing organs to areas where the resultant wounds do not interfere with insemination or oviposition. These data show that the dual functions of female genitalia (mating and oviposition) mediate genital coevolution.

A key determinant of the intensity of sexual selection acting on a trait is how variation in that trait is related to variance in reproductive success of individuals. This connection compels efforts to assess lifetime mating number and how it varies among individuals in a population. In the Lepidoptera, female mating success can be assessed relatively easily by counting by the number of spermatophores in the female's copulatory sac but male mating success in the field can often only be documented by observing copulations. Here we report a method for identifying whether or not males have recently mated that relies on the effect of mating on the appearance of the male's reproductive tract in the pipevine swallowtail, Battus philenor. In this species laboratory experiments reveal that during mating, components of a male's reproductive tract become shorter, decrease in mass, and change in appearance, irrespective of male age. These changes persist for at least two days after mating. After documenting these indicators of recent mating, we examined the reproductive tract of 68 field-caught males and found that twelve (17.6%) showed strong evidence of having mated recently. We found that older males were more likely to have recently mated. In addition, the color of the dorsal hindwing, a feature that females use in mate choice, was significantly greener in males, that according to our criteria, had recently-mated than in males that had not.

Sexual receptivity and mating behavior of the cabbage aphid parasitoid Diaeretiella rapae McIntosh were studied under laboratory conditions. When male and female D. rapae were paired females, males actively courted females, while females kept themselves away from males and displayed grooming behavior. Males became sexually active immediately after emergence and made mating attempts, whereas females took longer to become receptive to mating. Virgin males quickly detected female presence, resulting in a significant increase in the frequency of male courtship. Males encountered females within 5 min of pairing, and 90% of the males displayed courtship behavior by fanning their wings and chasing the female for mating. Before successful mating, males tended to approach females more often than females approached males. The time between pairing and mating in newly emerged females was longer than in 1-d-old females. The overall mating success in D. rapae was about 70%, and successful mating was largely dependent on females’ decision to mate. Unlike females, males remained sexually receptive after mating.

Based on the phenotype-linked fertility hypothesis, sexual selection should favour females that can accurately assess the recent mating history of available sexual partners and preferentially avoid mating with recently-mated males [who may be sperm depleted (SD)] so as to minimize the risk of their eggs not being fertilized. This hypothesis has received to date only limited attention and empirical support. Therefore, in the current study, we investigated experimentally whether females of a vertebrate species, the Trinidadian guppy (Poecilia reticulata), are able to assess the recent mating history of males, and thus potentially their functional fertility, and choose to avoid mating with males that appear to have recently mated and who may be sperm limited. Individual virgin females were first given a dichotomous choice between a male that had not been recently observed to interact sexually with another female (i.e. not sperm-depleted) and another male that had been observed to interact sexually with a female (i.e. potentially sperm-depleted) as sexual partners. Paired males were matched for body length and coloration. Immediately following this test, the focal females were subjected to a free-swimming mate-choice test using the same paired stimulus males. As predicted, on average, female guppies avoided the apparently recently-mated (and potentially sperm-depleted) male and exhibited a significant preference for the other male not recently observed mating (and thus not likely sperm limited) during both tests. We do not yet fully understand the underlying mechanisms of this preference. Therefore, further research on the particular cues that females use to assess the recent mating history and fertility status of males is required.

The success of vector control strategies aiming to decrease disease transmission via the release of sterile or genetically-modified male mosquitoes critically depends on mating between laboratory-reared males and wild females. Unfortunately, mosquito colonization, laboratory rearing, and genetic manipulations can all negatively affect male competitiveness. Heterosis is commonly used to produce domestic animals with enhanced vigor and homogenous genetic background and could therefore potentially improve the mating performance of mass-reared male mosquitoes. Here, we produced enhanced hybrid males of the malaria mosquito Anopheles coluzzii by crossing two strains colonized >35 and 8 years ago. We compared the amount of sperm and mating plug proteins they transferred to females, as well as their insemination rate, reproductive success and longevity under various experimental conditions. Across experiments, widespread adaptations to laboratory mating were detected in the older strain. In large-group mating experiments, no overall hybrid advantage in insemination rates and the amount of sperm and accessory gland proteins transferred to females was detected. Despite higher sperm activity, hybrid males did not appear more fecund. However, individual-male mating and laboratory-swarm experiments revealed that hybrid males, while inseminating fewer females than older inbred males, were significantly more fertile, producing larger mating plugs and drastically increasing female fecundity. Heterotic males also showed increased longevity. These results validate the use of heterosis for creating hybrid males with improved fitness from long-established inbred laboratory strains. Therefore, this simple approach could facilitate disease control strategies based on male mosquito releases with important ultimate benefits to human health.

During insect copulation, males typically transfer to females complex ejaculates that contain more than just sperm. These fluids can have a variety of effects on females (e.g., they can supply energy and nutrients, increase egg production and egg laying, inhibit female re-mating, and reduce female longevity). Although these effects of seminal fluid on females are often volume-dependent, and despite the several functions of seminal fluids, few studies have investigated the effects of mating duration on female reproductive traits. We therefore controlled mating duration and investigated the effects of seminal fluid on reproductive traits (lifetime fecundity, oviposition time, and oviposition rate) and longevity of females of the seed bug Togo hemipterus (Scott) (Heteroptera: Lygaeidae). All mated females laid eggs, even after a short mating duration (10 min). After a short mating duration, however, only approximately half of the females laid fertilized eggs, possibly because they did not receive sufficient sperm to fertilize all their eggs. These results showed that female egg laying was induced by such physical stimuli as penis insertion and stretch reception in the bursa copulatrix, or by male seminal products other than sperm. Males must continue ejaculation for 20 min or more to ensure fertilization of the female’s eggs. Although males ejaculated all their sperm within 20 min, a single insemination did not fertilize all of a female’s eggs throughout her lifetime. Females that copulated once laid eggs for approximately 40 days, but laid fertilized eggs for approximately the first 20 days only; we believe the sperm were depleted or became inactive. The positive correlation between mating duration and lifetime fecundity (including both fertilized and unfertilized eggs) and rate of oviposition (the number of eggs laid per day) indicated that the seminal substances stimulated female egg production and/or egg laying, and were transferred to females in a time-dependent manner. Males manipulated females by use of seminal substances. Mating duration did not affect female longevity. T. hemipterus males affected female reproductive traits in several ways. These seemingly manipulative substances are likely to be costly to females because they laid unfertilized eggs when sperm were depleted or became inactive.

The expected strong directional selection for traits that increase a male's mating ability conflicts with the frequent observation that within species, males may show extreme variation in sexual traits. These male reproductive polymorphisms are usually attributed to direct male-male competition. It is currently unclear, however, how directional selection for sexually selected traits may convert into disruptive selection, and if female preference for elaborate traits may be an alternative mechanism driving the evolution of male polymorphism. Here, we explore this mechanism using the polyandric dwarf spider Oedothorax gibbosus as a model. We first show that males characterized by conspicuous cephalic structures serving as a nuptial feeding device ("gibbosus males") significantly outperform other males in siring offspring of previously fertilized females. However, significant costs in terms of development time of gibbosus males open a mating niche for an alternative male type lacking expensive secondary sexual traits. These "tuberosus males" obtain virtually all fertilizations early in the breeding season. Individual-based simulations demonstrate a hitherto unknown general principle, by which males selected for high investment to attract females suffer constrained mating opportunities. This creates a vacant mating niche of unmated females for noninvesting males and, consequently, disruptive selection on male secondary sexual traits.

Reproduction induces non-trivial costs, such that both males and females should choose their mates carefully and invest their resources prudently. Male performance and thus their investment into ejaculates are often predicted to decrease with age and mating frequency, which may in turn negatively affect female fitness and thus feedback on the attractiveness of old males. Such reproductive senescence may be mediated by changes in the males’ oxidative status. Here, we investigated the effects of male mating frequency and age on male reproduction and oxidative status, and the respective consequences for female reproduction. We used the tropical butterfly Bicyclus anynana, in which counterintuitively older males have a higher mating success than younger ones. In once-mated males, spermatophore mass and sperm numbers strongly increased with age, while antioxidant defences and oxidative damage declined with age. In repeatedly mated males, spermatophore mass and sperm number showed little variation being similar to young once-mated males, while antioxidant defences increased and oxidative damage decreased with mating frequency. Female reproductive success was highest when mating with young once-mated males, although these produced small spermatophores with low sperm numbers. Our findings suggest that in B. anynana, (1) ejaculate size and sperm number are not reliable proxies of male quality, (2) ejaculate quality diminishes with age and mating number, and that (3) old male mating advantage likely results from sexual conflict owing negative effects on female fitness.

In insects with sex role reversal in mating, in which females actively court males, large and nutritious ejaculates are a common direct benefit to females. Such ejaculates are costly for males to produce and their size and composition can depend on male condition. However, the fitness effects to males and females of such condition-dependent provisioning are less clear. Here, we studied the effects of phenotypic condition on mating behaviour, ejaculate size and reproductive output in honeylocust beetles, Megabruchidius dorsalis. Our experimental design allowed us to disentangle the independent effects of juvenile resource acquisition in both sexes (as reflected by body size) and resource acquisition by adult males (feeding). We show that phenotypic condition of both sexes had sizeable independent and interactive effects on mating and reproductive output. In males, resources accrued during the juvenile phase had significant but relatively marginal effects on male mating and reproduction. Male adult feeding, in contrast, had sizeable effects on almost all aspects of male and female reproduction, through the nutritional effects of ejaculates in females. We discuss our findings in light of the reversal of both sex roles and sexual size dimorphism exhibited by this species, relative to related species. Our results highlight the importance of testing the interaction of male and female condition on components of fitness to understand the evolution and maintenance of mating systems.

In Calopteryx damselflies, males remove rivals’ sperm stored by the female, thereby reducing sperm competition. This behaviour may create a sexual conflict, because females could lose the sperm stored in the spermatheca, used for long-term storage. Comparative evidence suggested antagonistic coevolution between sexes, which might prompt the evolution of narrow spermathecal ducts, or longer spermathecae, hindering sperm removal. Calopteryx haemorrhoidalis and C. splendens coexist and sometimes hybridize. Therefore, here I predicted that if females coevolve with conspecific males, heterospecific males should have an advantage when interspecific matings occur because females will show less resistance to them than to conspecific males. By hand-pairing females to males of both species, I found that in intraspecific and interspecific matings, sperm was almost completely removed from the bursa (97–100%), but only partially from the spermathecae, with more spermathecal removal in interspecific (63–71%) than intraspecific matings (14–33%). This suggests that heterospecific males are more efficient in sperm removal as predicted by a sexually-antagonistic coevolutionary scenario. Furthermore, in most cases, only the left spermatheca was emptied, suggesting that the evolution of more than one spermatheca might also be a female counter-adaptation to regain control over fertilization.

Polyandry is commonly maintained by direct benefits in gift-giving species, so females may remate as an adaptive foraging strategy. However, the assumption of a direct benefit fades in mating systems where male gift-giving behaviour has evolved from offering nutritive to worthless (non-nutritive) items. In the spider Paratrechalea ornata, 70% of gifts in nature are worthless. We therefore predicted female receptivity to be independent of hunger in this species. We exposed poorly-fed and well-fed females to multiple males offering nutritive gifts and well-fed females to males offering worthless gifts. Though the treatments strongly affected fecundity, females of all groups had similar number of matings. This confirms that female receptivity is independent of their nutritional state, i.e. polyandry does not prevail as a foraging strategy.ConclusionsIn the spider Pisaura mirabilis, in which the majority (62%) of gifts in nature are nutritive, female receptivity depends on hunger. We therefore propose that the dependence of female receptivity on hunger state may have evolved in species with predominantly nutritive gifts but is absent in species with predominantly worthless gifts. Fil: Pandulli Alonso, Irene. Laboratorio de Etología, Ecología y Evolución. Instituto de Investigaciones Biológicas Clemente Estable; Uruguay Fil: Quaglia, Agustín Ignacio Eugenio. Universidad Nacional de Cordoba. Facultad de Medicina. Instituto de Virologia "Dr. J.M. Vanella". Laboratorio de Arbovirus; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Albo, Maria J.. Laboratorio de Etología, Ecología y Evolución. Instituto de Investigaciones Biológicas Clemente Estable; Uruguay

Females often mate with multiple males even when a single mating is sufficient to fertilize their eggs. Remating can lead to direct and indirect benefits for females, but these benefits trade-off against the potential costs associated with polyandry. There is a growing understanding that not all males are equal in their ability to deliver sperm to the site of fertilization. Such differences can arise both from environmental (e.g., mating history) and intrinsic (genetic) sources of variation. Most studies that investigate female fitness control male mating history to overcome such effects, but this control may bias interpretations of the benefits of polyandry. Here, we tried to avoid overestimating the benefits of polyandry that might accrue from mating repeatedly with virgin males. To do this, we quantified 6 components of fitness in female bruchid beetles, Callosobruchus maculatus, that were mated between 1 and 4 times to males with unknown mating histories, either in isolation or with rival males present. As copulation number increased, fecundity, offspring production, and egg-to-adult survival declined. In contrast to these short-term costs, the probability that a female remained completely infertile was highest at 1 copulation, and geometric mean fitness peaked after 3 copulations. Pericopulatory harassment by males did not affect female productivity. There was a significant interaction between this harassment and copulation number on longevity such that harassed females mating 2 or 3 times, and females mating twice in isolation, died soonest. Our results suggest that females may be selected to mate multiply despite short-term costs to fitness.

Male Japanese quail (Coturnix japonica) engage in vigorous same-sex sexual interactions that have been interpreted as aggressive behavior reflecting dominance relationships. The consequences of this behavior for reproductive success, and whether it is a form of competition over mating and fertilization, are unclear. Three experiments were conducted to determine the effect of seeing or interacting with another male on a male's subsequent mating and fertilization success with females. A vigorous interaction with another male in which the subject performed more cloacal contact movements (movements to try to make contact with the other bird's cloacal opening) reduced subsequent mating and fertilization success with a female to a similar extent as a prior mating with a different female. Receiving one or more cloacal contacts from another male was less detrimental for subsequent success. The mere presence of another (stimulus) male delayed mating initiation in those male subjects that approached the stimulus first instead of the female. These results do not support the idea that the male "on top" in male-male sexual interactions is the dominant bird who goes on to achieve greater reproductive success. Instead, the results are consistent with male-male sexual behavior as an occasionally costly by-product of strong mating motivation.

In nature, females of several animal taxa exhibit considerable variation in their mating system, and this variation involves different balances of costs (e.g., energetic, reproductive) and benefits (e.g., increased net reproductive rate of the female, increased longevity). Many studies have focused on discovering the potential advantages and disadvantages that females could have when increasing their mating rate and the possible evolutionary consequences that may result. Butterflies and moths are an ideal study system because it is easy to determine and to manipulate experimentally their mating frequency. In this study, the effect of continuous availability of different numbers of males (1, 2, 4, 8) on female mating rate and fitness components was estimated by comparing the number of spermatophores in the corpus bursa (an estimate of the number of copulations, but not of the number males involved in these copulations), female longevity, lifetime number of laid eggs (fecundity), and proportion of hatching eggs (fertility) in the moth Sangalopsis veliterna Druce (Lepidoptera: Geometridae). The results showed that there were no significant differences in either fertility or fecundity when treatments were compared, but longevity and in some cases fecundity increased when females had several matings. Resumen En la naturaleza, hembras de varios taxa animal muestran una variación considerable en su sistema de apareamiento, esta variación involucra diferentes costos (energéticos, reproductivos, etc) y beneficios (aumento de la tasa reproductiva neta de la hembra, mayor longevidad, entre otros). En años recientes, muchos estudios se han enfocado en descubrir las potenciales ventajas y desventajas que las hembras podrían tener al aumentar su número de cópulas y las posibles consecuencias evolutivas que podrían resultar. Las mariposas y polillas son un sistema de estudio ideal, dada la facilidad para determinar y manipular experimentalmente su frecuencia de apareamiento. En este estudio, el efecto de la disponibilidad continua de diferente número de machos (1, 2, 4, 8) sobre la frecuencia de apareamiento de las hembras y los componentes del potencial reproductivo (fitness) fueron estimados al comparar el número de espermatóforos hallados en la bursa copulatrix (un estimado del número de copulas, pero no del número de machos involucrados en estas copulas), la longevidad de las hembras, número de huevos colocados (fecundidad) y proporción de huevos fecundados (fertilidad) en la polilla Sangalopsis veliterna Druce (Lepidóptera: Geometridae). Los resultados indican que no existen diferencias en la fertilidad ni en la fecundidad; sin embargo la longevidad aumentó a medida que se las hembras presentaron más de una cópula y de igual manera en algunos casos la fecundidad aumentó con varios apareamientos.

We examined the female mating choice of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) when exposed to a male with which she had mated before vs. a novel male which she never encountered. After first mating, most females chose to remate with the same male and showed a shorter mating latency period to copulation with the familiar male as compared to a new male. Then, we allowed a female to mate once, 5× with the same, or 5× with different males to evaluate how different mating patterns influence the females’ reproductive performance and offspring fitness. Mating 5× with the same male or different males improved female egg production, but had no effect on hatching rate or offspring fitness. Our findings suggest that female C. montrouzieri are able to distinguish between familiar and unfamiliar males and prefer to mate with the former. Further, multiple mating appears to offer material benefits to female C. montrouzieri specifically by increasing fecundity.

SummarySex-specific elaborations are common in animals and have attracted the attention of many biologists, including Darwin [1]. It is accepted that sexual selection promotes the evolution of sex-specific elaborations. Due to the faster replenishment rate of gametes, males generally have higher potential reproductive and optimal mating rates than females. Therefore, sexual selection acts strongly on males [2], leading to the rapid evolution and diversification of male genitalia [3]. Male genitalia are sometimes used as devices for coercive holding of females as a result of sexual conflict over mating [4, 5]. In contrast, female genitalia are usually simple. Here we report the reversal of intromittent organs in the insect genus Neotrogla (Psocodea: Prionoglarididae) from Brazilian caves. Females have a highly elaborate, penis-like structure, the gynosome, while males lack an intromittent organ. The gynosome has species-specific elaborations, such as numerous spines that fit species-specific pouches in the simple male genital chamber. During prolonged copulation (∼40–70 hr), a large and potentially nutritious ejaculate is transferred from the male via the gynosome. The correlated genital evolution in Neotrogla is probably driven by reversed sexual selection with females competing for seminal gifts. Nothing similar is known among sex-role reversed animals.

Female reproductive status can have strong selective effects on male mating strategies due to the threat of sperm competition, which may explain why males prefer virgin over mated females. However, in mating systems with female multiple mating rates and mating plugs, males should not only respond to the risk but also to the level of sperm competition and should be sensitive to the interference from mating plugs. In the orb-web spider Argiope keyserlingi, females possess paired sperm-storage organs facilitating separate sperm storage from different males. Males are limited to 2 copulations due to mutilation of their paired genitals (pedipalps). By conducting binary choice experiments, we tested whether males of different mating status can distinguish between females that mated with 1 or 2 males and whether single-mated males discriminate between single-mated females with matched or unmatched virgin genital openings. Furthermore, we investigated whether males adapt their mating strategies to the intensity of sperm competition by providing males with varying qualities of females in their immediate vicinity. Our results demonstrated that males are sensitive to the level of sperm competition and preferred single-mated females over double-mated females. However, they failed to identify single-mated females whose virgin genital opening matched their unused pedipalp, which is required due to their fixed ipsilateral insemination. Surprisingly, males never mated twice with the same female independently of the quality of surrounding females. This suggests that the benefits from searching and mating with a different female are greater than the benefits of monopolizing the female by mating twice with her.

Immune responses against opportunistic pathogens have been extensively studied in Drosophila, leading to a detailed map of the genetics behind innate immunity networks including the Toll, Imd, Jak-Stat, and JNK pathways. However, immune mechanisms of other organisms, particularly plants, have primarily been investigated using natural pathogens. It was the use of natural pathogens in plant research that revealed the plant R/Avr system, a specialized immune response derived from antagonistic coevolution between plant immune proteins and their natural pathogens’ virulence proteins. Thus, we recommend that researchers begin to use natural Drosophila pathogens to identify novel immune mechanisms that may have arisen through antagonistic coevolution with common natural pathogens. In this review, we address the benefits of using natural pathogens in research, describe the known natural pathogens of Drosophila, and discuss exciting prospects for future research on select natural pathogens of Drosophila.

The present study investigates the coevolution of a particular male genital process and the female spermathecal ducts in a clade of stalk-eyed flies (Diptera, Diopsidae) and debates the underlying evolutionary mechanisms. The fine morphology and interaction of the male and female genitalic structures are reconstructed from serial sections of mating pairs in one of the species. It is found that the male genital process traverses the common spermathecal duct to enter the base of one of the separate spermathecal ducts during the mating. Spermatozoa and accessory secretions are not transferred through the male genital process but can be discharged only from the male gonopore near its base. A detailed morphometric study reveals low intraspecific variation and hypoallometry of the male genital process. Across 17 species studied comparatively, the lengths of the male genital process and the female common and separate spermathecal ducts are highly variable. The length of the male genital process is correlated significantly with that of the female common spermathecal duct, but not with that of the separate spermathecal ducts. Based on the combined evidence it is concluded that the male genital process and the female common spermathecal duct have coevolved, and that sexual selection by cryptic female choice constitutes a possible and parsimonious explanation for their coevolution. Alternative or additional explanations in terms of sexually antagonistic coevolution cannot be ruled out conclusively, but are not supported by the available evidence.

The correlated evolution of genitalia between sexes has been demonstrated in many taxa. However, it remains unclear whether female rather than male genitalia can play a key role in the correlated evolution of male and female genitalia. We conducted an extensive cross-population analysis of the divergence patterns of genital structures, weights of whole genital organs, and the bodies of both sexes, and male genital length in a group of xystodesmid millipedes showing diverse genital morphologies. We demonstrate that the correlated evolution of male and female genitalia toward exaggerated states has occurred in the millipedes, which have evolved novel traits in both males (forceps-like gonopods) and females (retractable bellows). Enlargement and elongation of forceps-like gonopods may be advantageous in sperm competition, whereas enlargement and elongation of the bellows may facilitate acceptance/rejection of insemination for ensuring the female's fitness. These male and female genital parts have affected the correlated evolution in the opposite sex, resulting in diversification and exaggeration of genital morphology. Our study suggests that evolutionary novel traits in not only males but also in females could play an important role in the correlated evolution of genitalia between the sexes.

Dermaptera (earwigs) is a relatively small polyneopteran order with approximately 2200 described species. They are characterized by a pair of forceps, which are hardened, unsegmented cerci at the caudal end of the abdomen. In most species, males have more exaggerated forceps than females, indicating an effect of sexual selection on them. Earwigs also exhibit astonishing diversity in the number, laterality and size of both male and female genital components. This characteristic has promoted the study of postcopulatory sexual selection in several representative species. Here, previous studies of earwigs that examined pre- and postcopulatory sexual selection are reviewed in detail. Related topics included here are sexually antagonistic coevolution, evolution of laterally asymmetrical morphologies, and developmental aspects of intra-sexually dimorphic traits. A new terminology system for male genitalia is also proposed.

To the extent that sperm production or mating opportunities are limited, males are expected to allocate their sperm optimally, so as to increase their overall fitness. Among spiders, sperm depletion and monogyny are known to be optimal male mating decisions either under strong sperm competition or as terminal investment strategies, when future mating opportunities are limited. In a medium-sized wolf spider, Hogna radiata (Latreille 1817), we investigated sperm depletion, terminal sperm investment and the potential for sperm competition in laboratory mating trials in which we allowed males and females to pair sequentially with two mates. Males mated with as many females as they encountered. We found no evidence of sperm depletion or terminal sperm investment, as mating duration and female fitness were unaffected by male mating history or age. Polyandry was rare and did not involve any clear fitness benefit to females, whereas premating sexual cannibalism was a rather common outcome of mating interactions involving inseminated females. Our results indicate that H. radiata males are not sperm limited and support the hypothesis that the potential for sperm competition shapes the evolution of sperm allocation in this species. Monandrous females do not incur any fitness cost and could potentially benefit from cannibalizing their prospective mates., This study was financially supported by the Spanish Ministerio de Educación y Cultura to C.F.M. (BSO2002-03264).

Graphical abstract, Highlights • Many reproductive traits are shared across the sexes. • Shared traits can be influenced by both sexes or just one. • We identified male-specific control of mating duration in response to sexual competition in fruitflies. • Male-specific control is associated with significant male fitness benefits and could arise because of sexual conflict., Males of many species assess the likely level of sperm competition and respond adaptively, for example by increasing the level of courtship they deliver, by transferring more sperm or seminal fluids or by extending matings. In mechanistic terms, it may be easier for males to adjust the level of their investment to the likely level of sperm competition for male-limited traits such as sperm and seminal fluid production over which they have control. However, for shared traits, such as mating duration, that are expressed at a level determined by direct interactions between males and females, adaptive responses by males to competition could be constrained. This need not be the case, however, if males have significant influence over the expression of such traits. Understanding which sex can most influence the expression of shared traits in response to sexual competition is important in order to document the range of strategic, plastic responses that are available to each sex. However, direct tests of these ideas require, as in this study, measurements of the effect on a shared trait of manipulating the ability of one, but not the other, sex to influence it. We studied the responses of male Drosophila melanogaster to sexual competition, in which mating duration is increased following exposure to rivals, resulting in significantly increased paternity share. Males were allowed to respond normally to the presence of rivals prior to mating, but female responses to males were reduced via decapitation and immobilisation. We found that matings with both intact and decapitated, immobilised females were significantly longer with males that had been exposed to rivals prior to mating. Hence males could maintain their responses to rivals with intact and decapitated females, suggesting significant male influence over the ability to extend mating duration in this context. However, overall, mating duration was significantly longer with intact in comparison to decapitated females. Whether this is due to a female influence over mating duration in general, or whether males respond differently to immobilised females, is not yet known. Gaining a fuller understanding of sex-specific control of plastic traits will be important in the future for understanding how reproductive traits evolve and function.

In sex-role-reversed species, sexual selection acts more strongly on females than on males, a situation that can result in the evolution of secondary sexual traits in females and strong mating preferences in males. While some research exploring mating preferences in sex-role-reversed species has been conducted, overall, this topic remains relatively unexplored. The Gulf pipefish, Syngnathus scovelli, is a highly polyandrous pipefish species. Sexual selection is significantly stronger in females than in males, which has led to the evolution of both morphological and behavioral female secondary sexual traits. However, because males gestate the offspring in specialized pouches and make a substantial investment in embryos during development, females may also benefit from being choosy. The goal of this study was to examine both male and female mating preferences in this species. We found that male mating preference was significantly associated with female courtship behavior. Larger females were also able to maintain these behaviors for longer intervals than smaller females. No evidence of female mating preference in regard to male size was observed but the data suggest that male behaviors may be providing positive reinforcement to courting females. This research provides further insight into how mate preferences vary among sex-role-reversed species.

Understanding mating behavioral sequence helps us identify the mechanisms of mate assessment and choice, and better evaluate behavior-based pest control strategies. Here we describe the mating behavior of Cnephasia jactatana Walker whose females release a sex pheromone, and determine the effect of male mating status on reproductive success. The mating sequence starts when males approach females and display courtship behavior with antennation and fanning wings. Both males and females may end a mating attempt at any stage of the sequence. Both sexes assess their mates from the initial contact to copulation. Females appear to be choosier at the early and mid-stages than at the late stage of the sequence. Virgin males approach and court females significantly earlier than nonvirgin males. As compared with nonvirgin males, virgin males are ≈1.6 times more likely to approach and 1.8 times more likely to court females, and four times more likely to achieve mating. This may be attributed to depletion of s...

Mating behavior and sexual selection in relation to morphometric traits in a polygamous beetle, Glenea cantor (F.) (Coleoptera: Cerambycidae), were investigated. Upon encounter, a male approached a female, mounted her, grasped her terminal abdomen with his hind tarsi, and attempted to mate. Successful mating lasted about 3.5 h. Although all traits measured in females and half of traits in males were significantly correlated with mating success, the primary selection on virgin females was the genital trait, the bursa copulatrix length, and that on males was the body length and hind tarsal length. Longer bursa copulatrix accommodated a larger ejaculate, suggesting that this female trait benefits the male that first mates with the female in terms of increasing ejaculate size to beat subsequent males in sperm competition. Under a female-biased sex ratio, more than 20% of matings failed within 20s after the male genitalia had been inserted into hers, suggesting that males assess genital features of the female before insemination and undertake cryptic male mate choice. Larger males were more capable of grasping females and achieving mating. During the premating struggle the male almost always used his hind tarsi to lift the female terminal abdomen to the position for his genitalia to insert, and as a result, males with longer hind tarsi achieved higher mating success.

Traumatic mating (or copulatory wounding) is an extreme form of sexual conflict whereby male genitalia physically harm females during mating. In such species females are expected to evolve counter-adaptations to reduce male-induced harm. Importantly, female counter-adaptations may include both genital and non-genital traits. In this study, we examine evolutionary associations between harmful male genital morphology and female reproductive tract morphology and immune function across 13 populations of the seed beetle Callosobruchus maculatus . We detected positive correlated evolution between the injuriousness of male genitalia and putative female resistance adaptations across populations. Moreover, we found evidence for a negative relationship between female immunity and population productivity, which suggests that investment in female resistance may be costly due to the resource trade-offs that are predicted between immunity and reproduction. Finally, the degree of female tract scarring (harm to females) was greater in those populations with both longer aedeagal spines and a thinner female tract lining. Our results are thus consistent with a sexual arms race, which is only apparent when both male and female traits are taken into account. Importantly, our study provides rare evidence for sexually antagonistic coevolution of male and female traits at the within-species level.

To increase fertilization chances compared with rivals, males are favoured to transfer accessory gland proteins to females during mating. These substances, by influencing female physiology, cause alteration of her sperm usage and remating rate. Simultaneously hermaphroditic land snails with love-darts are a case in point. During courtship, a love-dart is pierced through the partner's body wall, thereby introducing accessory mucous gland products. This mucus physiologically increases paternity by inhibiting the digestion of donated sperm. The sperm, which are packaged in a spermatophore, are exchanged and received in an organ called the diverticulum. Because of its length, this organ was previously proposed to be a female anatomical adaptation that may limit the dart interference with the recipient's sperm usage. For reproductive success of the donor, an anatomically long spermatophore, relative to the partner's diverticulum, is beneficial as sperm can avoid digestion by exiting through the spermatophore's tail safely. However, the snail Eobania vermiculata possesses a diverticulum that is three times longer than the spermatophore it receives. Here, we report that the love-dart mucus of this species contains a contraction-inducing substance that shortens the diverticulum, an effect that is only properly revealed when the mucus is applied to another helicid species, Cornu aspersum. This finding suggests that E. vermiculata may have evolved a physiological resistance to the manipulative substance received via the love-dart by becoming insensitive to it. This provides useful insight into the evolution of female resistance to male manipulations, indicating that it can remain hidden if tested on a single species., Summary: The effect of accessory gland proteins transferred on the love-dart of land snails can remain hidden within a species as a result of physiological female resistance to male manipulation.

The fruit fly Drosophila melanogaster has short time life span, these flies, are particular advantage for ageing work, including , life history which divided up into distinct, morphological stages so that the period growth and development can be readily distinguished from the sexual mature ageing adult phase. Sexual selection aging means differential reproduction owing variation in the ability to obtain mates and fertilized oocytes. A few experimental studies have shown that the optimum strategy for males is often to mate with as many females as possible, whereas the optimum strategy for females is likely to select the most attractive male. As a result the mating males to females, the repetitive of mating is very important on the rate of fertility of females, if males has been twice mating by females usually the fertility will be decreased, here the function some secretion from ejaculate of males is very important. Recently the performance of male accessory gland proteins (Acps) were found in Drosophila melanogaster. Acps have been observed cause of increasing female oviposition rates, also increasing the rate of fertility, hatchability, son mating ability, mediate sperm storage, cause part of the survival cost mating male to females, may protect reproductive tracts or gametes from microbial attack, and also hundreds function known and unknown on the reproductive performance in males and females. However, until to date were found almost 25 to 150 proteins in male accessory glands, but also still were not distinguished function of all those proteins. Supporting these hypotheses, here we study the function of ageing on the rate of male sexual secretion and reproductive performance in offspring fitness. The objective of the current study is two-fold: the first aim is to evaluate mechanisms of sexual selection on the age affective in parental traits and second aim, is to evaluate mechanisms of sexual selection on the offspring fitness traits for their potential explained by random mating in the species Drosophila melanogaster.

The processes underlying reproductive isolation, and the traits involved, are the subject of considerable debate in evolutionary biology. Studying the costly sexual interaction of species in secondary sympatry, a phenomenon known as reproductive interference, can help to shed light on past and present isolating mechanisms, as well as the implications of sympatry for individual fitness. We investigated the roles of two sets of traits, genitalic and behavioural, in reproductive isolation and interference in two species of Australian neriid flies, Telostylinus lineolatus and T. angusticollis. Surprisingly, although these species differ markedly in male but not in female genitalia, we found evidence that genital morphology resulted in asymmetric reproductive isolation: T. lineolatus males could transfer sperm to T. angusticollis females, but T. angusticollis males were unable to transfer sperm to T. lineolatus females. However, neither type of cross produced any viable hybrids. Behavioural responses also contributed asymmetrically to both reproductive isolation and reproductive interference. Males pursued both conspecific and heterospecific females. Females of both species discriminated against heterospecific males, but T. lineolatus females exhibited stronger discrimination than T. angusticollis females. Curiously, T. angusticollis males both fought and attempted to copulate with T. lineolatus males, resulting in reduced mating success for T. angusticollis males with conspecific females. Our findings show that both genitalic and behavioural traits can play important roles in reproductive isolation, but the consequences of interspecific divergence in these traits can be surprisingly complex, resulting in asymmetric effects on many aspects of interspecific interactions.

In water striders, the interests of both sexes diverge over the decision to mate, leading to precopulatory sexual conflict. The influence of mating rate and key persistence and resistance traits on reproductive success has seldom been investigated in the context of multiple matings. We used amplified fragment length polymorphism (AFLP) based genetic parentage analyses to estimate mating and reproductive success in Gerris gillettei Lethierry and Severin, 1896, while allowing for free multiple matings. We tested the hypotheses that males should display stronger opportunity for sexual selection and steeper Bateman gradients. In each sex, persistence and resistance traits should also impact mating and reproductive success. Surprisingly, males and females had similarly high and variable effective mating rates (i.e., number of genetic partners), and both sexes produce more offspring when mating with more partners. As predicted, exaggerated persistence traits allowed males to mate with more partners and sire more offspring. However, we found no evidence for an impact of resistance traits for females. The mating environment may have favoured low resistance in females, but high promiscuity can be beneficial for females. This first description of the genetic mating system for a water strider species suggests that the determinants of fitness can be further deciphered using the sexual selection framework.

Mating frequency and the amount of sperm transferred during mating have important consequences on progeny sex ratio and fitness of haplodiploid insects. Production of female offspring may be limited by the availability of sperm for fertilizing eggs. This study examined multiple mating and its effect on fitness of the cabbage aphid parasitoid Diaeretiella rapae McIntosh (Hymenoptera: Aphidiidae). Female D. rapae mated once, whereas males mated with on average more than three females in a single day. The minimum time lag between two consecutive matings by a male was 3 min, and the maximum number of matings a male achieved in a day was eight. Sperm depletion occurred as a consequence of multiple mating in D. rapae. The number of daughters produced by females that mated with multiple-mated males was negatively correlated with the number of matings achieved by these males. Similarly, the proportion of female progeny decreased in females that mated with males that had already mated three times. Although the proportion of female progeny resulting from multiple mating decreased, the decrease was quicker when the mating occurred on the same day than when the matings occurred once per day over several days. Mating success of males initially increased after the first mating, but then males became ‘exhausted’ in later matings; their mating success decreased with the number of prior matings. The fertility of females was affected by mating with multiple-mated males. The study suggests that male mating history affects the fitness of male and female D. rapae.

Multiple mating by individuals successful in sexual competition results in other individuals failing to mate. This leads to sexual selection within a sex, typically the males. However, more species are coming to light in which females are subject to sexual selection. We review the contexts for and nature of sexual selection on females in several insect species where female mating failures have been noted. We then examine evidence of mating failures in two groups of insects, empidid flies (Diptera) and tettigoniid Orthoptera (katydids), in which sexual selection is expected to be relatively stronger on females. Using data from the field, we show for two species of katydids that, as predicted, there are mating failures by females in populations in which the direction of sexual selection appears to be reversed, but not in populations where sexual selection appears to be stronger on males.

Multiple mating often imposes direct fitness costs on females but can provide indirect benefits such as enhanced genetic diversity and offspring quality. The costs and benefits of multiple mating have been investigated extensively in separate-sex species but less so in simultaneous hermaphrodites, despite being highly relevant given their flexible resource allocation and ability to compensate for costs experienced in one sexual role by gains in the opposite role. At high mating rates, the promiscuous hermaphroditic pond snail Lymnaea stagnalis experiences depressed female fecundity mediated by seminal fluid compounds. By experimentally manipulating mating opportunities, we tested for effects on female reproductive investment over 10 weeks. As expected, continuous access to mating partners resulted in decreased female investment, in terms of both total number of eggs (fecundity) and egg mass dry weight. Total investment in offspring increased over time for all treatments but was significantly less pronounced in treatments with continuous access to partners, and this was irrespective of partner identity. Investment per offspring was positively correlated with higher mating rates across treatments. Thus, multiple mating resulted in higher investment in egg masses at low than at higher mating rates. In contrast, at higher mating rates the investment per egg was higher. We conclude that, in L. stagnalis, mating multiply can severely impact female reproductive success and, although we cannot entirely exclude reallocation of resources to the male function from this study, we argue that this is probably the result of sexual conflict caused by previously identified seminal fluid components. © 2012 The Association for the Study of Animal Behaviour.

The paradigm that females produce few costly eggs, whereas males produce an unlimited quantity of sperm holds true when matings are dispersed over time and males can replenish their sperm supply. In such a system, the best strategy for males is to mate with as many females as possible, as more is always better. However, in parasitoid species, mating often occurs at the emergence site and males may have to mate successively several females in a short period of time. This can lead to sperm depletion that can be temporary in synspermatogenic species whose males produce sperm throughout their adult life, or definitive in prospermatogenic species whose males emerge with their full sperm complement and do not produce more during their adult life. Both the spermatogeny index and the mating structure of a species will therefore influence the probability and intensity of sperm depletion in males. Sperm-limited males can court and mate females even in prospermatogenic species. These males still gain some inclusive fitness by preventing competitor males to fully inseminate females, therefore increasing the representation of their daughters in the following generation. Females that mate with partially or completely sperm-depleted males produce a constrained sex ratio that decreases their lifetime fitness. In species where sperm-depleted males occur, female choosiness based on sperm supply is predicted, as the cost of mating sperm-depleted males can be high. In addition, males are also expected to be choosy in prospermatogenic species as mating with sub-optimal females can be costly when sperm is limited.