The evolution and significance of male mate choice

Human-induced pheromone pollution leads to changes in alternative mating tactics of moths

Environmental changes driven by anthropogenic activities often disrupt animal communication and mating behavior. Consequently, these changes may force animals to adopt alternative mating tactics and strategies to find a mate. The mating disruption technique is an environmentally friendly tactic often used to control the pink-bollworm moth population in cotton fields. Though mating disruption is eco-friendly, it represents a Human-Induced Rapid Environmental Change for the targeted moths. Mating disruption involves spreading a synthetic version of the species-specific sex pheromone in the field, creating a pheromone-polluted environment, making it difficult for male moths to locate females and thereby reducing mating rates. We hypothesized that the intense sexual selection and environmental changes affecting communication would lead moths to increase their use of alternative mating strategies. An observed alternative mating behavior in male pink bollworm moths is disturbing mating pairs to displace the male and mate with the female. We compared this behavior between two populations and found that males long exposed to mating disruption disturbed mating pairs more frequently than those never exposed to it. In addition, males with a prolonged history of exposure to mating disruption showed reduced choosiness of females and increased their mating rate with small females of lower reproductive potential. The success rate of the observed couple disturbance was low. Nonetheless, this strategy, alongside other strategies, may contribute to the males' reproductive success when facing the additional challenge of locating females due to the pheromone-polluted environment.

Strategic use of male alternative reproductive tactics in cooperatively breeding banded mongoose groups

Alternative reproductive tactics (ARTs) allow less competitive individuals to reproduce by avoiding direct fights through sneaky strategies. Within cooperatively breeding groups ARTs are rarely reported, potentially owing to observational difficulties or reproductive suppression by group members. In societies where mating opportunities cannot be monopolized by one male, young males could use sneaky tactics as an intermediate 'stepping-stone' tactic to gain limited reproductive success while growing in resource-holding potential (RHP). Using decades of pedigree, weight, group demography and behavioural data, we investigated the use of sneaky 'sneaker' ARTs in wild male banded mongooses. In this species, groups typically contain more adult males than breeding females, leading to intense male-male competition. Instead of as a stepping-stone, sneaking tactics were typically used by males who had been displaced from mate-guarding status by stronger rivals. Additionally, sneakers had lower siring success compared with mate guards, despite similar weight loss costs, which may explain why males typically avoided reproductive activity entirely rather than sneaking. However, young sneakers gain access to older, higher fecundity females in the group and sneaking may even facilitate inbreeding avoidance. Overall, ARTs in stable social groups can predictively emerge from changes in relative RHP and social status over the lifetime.

Indirect evidence of an early mating advantage in wild cooperatively breeding male banded mongooses

Promiscuous females reduce male reproductive control. Males can attempt to monopolise access to these females, but distractions and sneaky rivals mean extra copulations cannot always be blocked. By mating first, males can obtain a headstart in sperm competition, but this may be negated by sperm storage and cryptic female choice mechanisms. We carry out an indirect rare test of an early mating advantage in a population of free-living wild animals. Using Bayesian GLMM analysis of a long-term life history database spanning 17 years, we show that banded mongoose males who interacted with females in earlier days of oestrus had a higher chance of siring their offspring compared with later rivals. An early mating advantage would intensify initial male-male competition and hence selection for male choice, as any initial mistake identifying preferred mating partners could see paternity lost to rivals.

Genetic variation in age-dependent attractiveness in a fish with a mixed mating system

Reproductive senescence is common across taxa and females often show a predictable decline in fecundity after maturity. Attending to these age-dependent cues could help males make optimal mate choice decisions. Here, we examined reproductive senescence and male mate choice in the androdioecious mangrove rivulus (Kryptolebias marmoratus), where self-fertilizing hermaphrodites exist with rare males. Hermaphrodites showed a strong decline in fecundity as they aged and genetic lineages varied in their fecundity at both young and old ages. Surprisingly, when given a simultaneous choice between genetically identical old and young hermaphrodites, males did not simply prefer younger hermaphrodites. Instead, male preference for younger versus older partners depended on the genetic lineage of the partners, resulting in a strong genotype × age interaction. For some genetic lineages, hermaphrodites were more attractive to males when younger, but for other genetic lineages, hermaphrodites were more attractive when older. Our results suggest that the genetic identity of the partner is key to how males weigh age-dependent changes in fecundity and that males are able to assess genetic variation in attractiveness over a partner's reproductive lifespan. Exploring how gamete viability and outcrossing are affected by age across genetic lineages could help us further understand these male preferences.

Genetic Variation in Male Mate Choice for Large Females in Drosophila melanogaster

Males in many species show courtship and mating preferences for certain females over others when given the choice. One of the most common targets of male mate choice in insects is female body size, with males preferring to court and mate with larger, higher-fecundity females and investing more resources in matings with those females. Although this preference is well-documented at the species level, less is known about how this preference varies within species and whether there is standing genetic variation for male mate choice within populations. We used hemiclonal analysis in the fruit fly, Drosophila melanogaster, to test for heritable genetic variation in pre- and postcopulatory components of male mate choice for large females. We found additive genetic variation for both forms of male choice: Males from different hemiclone lines varied in the strength of their courtship preferences for large females and the degree to which they extended matings with large females. Although males from hemiclone lines with stronger courtship preferences for large females were more likely to mate with those females, there was no genetic correlation between pre- and postcopulatory components of male mate choice, suggesting that they are under independent genetic control. Genetic variation in male mate choice may be widespread, potentially impacting the fitness of both sexes and the adaptive evolution of populations.

Electroantennographic and behavioral responses of Bactrocera dorsalis (Diptera: Tephritidae) adults to the volatiles of plum fruits

Fruit volatiles play a crucial role in the host localization by the oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae). This study focused on identifying the fruit volatiles from Sanyue plum and Sanhua plum (Prunus salicina Lindl.), which are 2 varieties of the same species, and examined their impact on the behavior of B. dorsalis by using a Y-olfactometer. A total of 35 and 54 volatiles from Sanyue plum and Sanhua plum were identified, respectively. Among these, 23 volatiles elicited electroantennographic (EAG) responses by B. dorsalis adults, showing concentration-dependent effects in males and females. Ethyl butyrate, butyl acetate, butyl hexanoate, ethyl caproate, ethyl hexanoate, and hexyl acetate significantly attracted B. dorsalis compared to liquid paraffin, while nonaldehyde was avoided. There was no significant difference in the behavioral responses of both sexes to sorbitol esters, hexyl isobutyrate, and 1-tetradecene compared with the control liquid paraffin group. Interestingly, (3Z)-C-3-hexenyl acetate significantly attracted females, but not males. The above findings suggest that plum fruit volatiles are likely to facilitate the localization of host fruit by B. dorsalis adults and may even aid in mate-finding. This study opens up new avenues for exploring novel plant-based attractants that might be of value for the integrated management of B. dorsalis.

Wasted Efforts Impair Random Search Efficiency and Reduce Choosiness in Mate-Pairing Termites

AbstractRandom search theories predict that animals employ movement patterns that optimize encounter rates with target resources. However, animals are not always able to achieve the best search strategy. Energy depletion, for example, limits searchers' movement activities, forcing them to adjust their behaviors before and after encounters. Here, we investigate the cost of mate search in a termite, Reticulitermes speratus, and reveal that the costs associated with mate finding reduce the selectivity of mating partners. After a dispersal flight, termites search for a mating partner with limited reserved energy. We found that their movement activity and diffusiveness progressively declined over extended mate search. Our data-based simulations qualitatively confirmed that the reduced movement diffusiveness decreased the searching efficiency. Also, prolonged search periods reduced survival rate and the number of offspring. Thus, mate search has two different negative effects on termites. Finally, we found that termites with an extended mate search reduced the selectivity of mating partners, where males immediately paired with any encountering females. Thus, termites dramatically changed their mate search behavior depending on their internal states. Our finding highlights that accounting for the searchers' internal states is essential to fill the gap between random search theories and empirical behavioral observations.

Males discriminate between substrate-borne cues of conspecific females based on age and mating status in the jumping spider, Habronattus brunneus

Sexual selection is often studied with a focus on female mate choice, wherein females evaluate male signals to select an optimal mate. However, in some systems, males should also make careful decisions about the females they choose to court, particularly when faced with the risk of precopulatory sexual cannibalism. Here, we explore the idea that male jumping spiders (Habronattus brunneus) may mitigate this risk by responding to female cues probably associated with female aggression and/or receptivity. We tested mature male spiders' ability to discriminate between substrate-borne cues (i.e. silk and excreta) produced by conspecific females of different ages and mating statuses. We found that males spent more time exploring cues produced by mature, non-mated females compared with either immature females or mated females. Heightened interest in cues produced by females that are sexually mature but not yet mated may allow males to reduce cannibalism risk, reduce wasted courtship effort and increase their reproductive success. The use of chemical and/or tactile cues in jumping spider courtship behaviour has been vastly understudied compared with the ways they use vision; this study provides the groundwork for understanding how these sensory modalities interact.

Comparative analysis reveals assortative mate preferences in darters independent of sympatry and sex

A preference for mating with conspecifics over heterospecifics is fundamental to the maintenance of species diversity in sexually reproducing organisms. This type of positive assortative preference results in sexual isolation, and a reduction in gene flow between species due to differences in mate choice. The proximate and ultimate causes of sexual isolation therefore constitute active areas of research in evolutionary biology. Sexual isolation is often stronger between closely related sympatric species as compared to allopatric species because of processes such as reinforcement. In addition, traditional theories of sexual selection suggest that because reproduction is more costly to females, they should be the choosier sex and play a more central role in sexual isolation. We conducted a comparative analysis of assortative mate preferences in males and females of sympatric and allopatric species pairs of darters (fish genus Etheostoma). We performed a meta-analysis of 17 studies, encompassing 21 species, in which assortative preference was measured when fish were (in most cases) allowed only visual information. As expected, we found stronger preferences for conspecifics over heterospecifics across studies and species. However, we did not find an effect of sympatry or sex on the strength of preference for conspecifics, but rather remarkable variation across species. We offer several testable hypotheses to explain the variation we observed in the strength of assortative preference.

Comparative transcriptome analysis of differentially expressed genes and pathways in male and female flowers of Fraxinus mandshurica

Fraxinus mandshurica Rupr. (F. mandshurica) is a dioecious tree species with important ecological and application values. To delve deeper into the regulatory pathways and genes responsible for male and female flowers in F. mandshurica, we conducted transcriptome sequencing on male and female flowers at four distinct stages. The analysis revealed that the female database generated 38,319,967 reads while the male database generated 43,320,907 reads, resulting in 2930 differentially expressed genes with 1441 were up-regulated and 1489 down-regulated in males compared to females. Following an analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), four distinct pathways (hormone signal transduction, energy metabolism, flavonoid biosynthesis, and photoperiod) linked to female and male flowers were identified. Subsequently, qRT-PCR verification revealed that FmAUX/IAA, FmEIN3, and FmA-ARR genes in hormone signal transduction pathway are related to female flower development. Meanwhile, FmABF genes in hormone signal transduction pathway, FmGS and FmGDH genes in energy metabolism pathway, FmFLS genes in flavonoid biosynthesis pathway, and FmCaM, FmCRY, and FmPKA genes in photoperiod pathway are related to male flower development. This study was the first to analyze the transcriptome of male and female flowers of F. mandshurica, providing a reference for the developmental pathways and gene expression levels of male and female plants.

Sexual conflict and sexual networks in bed bugs: the fitness cost of traumatic insemination, female avoidance and male mate choice

Sexual conflict is prevalent among animals and is primarily caused by the fact that the optimal mating rates are often higher in males than in females. While there is a growing appreciation that females can also gain from multiple matings, we still know relatively little about which sex controls the observed mating rates and how close it is to the optimal female mating rates. To address this issue, we tracked female bed bugs (Cimex lectularius) inseminated daily versus weekly and found that weekly inseminated females lived longer and produced over 50% more offspring. In a follow-up experiment employing a social network framework, we placed 24 bed bugs into a semi-naturalistic arena and recorded all sexual interactions. While recently inseminated females did not avoid males more often, they were more frequently rejected by males. Finally, we tracked avoidance behaviour in a single cohort of female bed bugs as they received six successive daily inseminations. Avoidance rates increased and insemination durations decreased with increasing number of prior inseminations. Overall, our results indicate high costs of polyandry. Although females possess some plastic avoidance strategies, the observed rates of insemination fall closer to the male rather than female optimum.

Lie to me to lay with me: Females deceive males via terminal investment

Historically, males have frequently been portrayed as the manipulative and deceptive gender, while females are often seen as adopting a coy and passive role. In this context, it is proposed that males use a terminal investment strategy, misleading females about their true poor condition, while females passively opt to mate with these deceptive males. However, we hypothesize that females in suboptimal condition may also engage in a terminal investment strategy by mimicking or enhancing their attractiveness to match that of females in better conditions. We studied this hypothesis in Tenebrio molitor, by subjecting females to three varying doses of lipopolysaccharides of Escherichia coli (LPS; 0.25, 0.5, or 1 mg ml-1), or three doses of the pro-oxidant Paraquat (PQ; 20, 40 or 80 mM), and subsequently assessing their survival and attractiveness to males. The LPS treatments and 20 mM of PQ had no significant effect on the survival or attractiveness of the females. However, females treated with 40 or 80 mM PQ survived fewer days compared to the control group. Those injected with 40 mM were more attractive than their control counterparts, while those treated with 80 mM were less attractive. Since the identical doses of LPS, which induce terminal investment in males, had no effect on females, we suggest sexual dimorphism in terminal investment. Furthermore, similar to males, if the stressor reaches a sufficiently high level, the signal becomes honest. These findings highlight how the quantity of stressors influences support for the terminal investment strategy in both males and females. Notably, this study challenges prevailing notions regarding gender roles in sexual selection, indicating that females, not just males, conceal their poor condition to attract mating partners.

Sub-acute exposure of male guppies (Poecilia reticulata) to environmentally relevant concentrations of PFOA and GenX induces significant changes in the testis transcriptome and reproductive traits

Poly- and perfluoroalkyl substances (PFAS) are frequently detected in the environment and are linked to adverse reproductive health outcomes in humans. Although legacy PFAS have been phased out due to their toxicity, alternative PFAS are increasingly used despite the fact that information on their toxic effects on reproductive traits is particularly scarce. Here, we exposed male guppies (Poecilia reticulata) for a short period (21 days) to an environmentally realistic concentration (1 ppb) of PFOA, a legacy PFAS, and its replacement compound, GenX, to assess their impact on reproductive traits and gene expression. Exposure to PFAS did not impair survival but instead caused sublethal effects. Overall, PFAS exposure caused changes in male sexual behaviour and had detrimental effects on sperm motility. Sublethal variations were also seen at the transcriptional level, with the modulation of genes involved in immune regulation, spermatogenesis, and oxidative stress. We also observed bioaccumulation of PFAS, which was higher for PFOA than for GenX. Our results offer a comprehensive comparison of these two PFAS and shed light on the toxicity of a newly emerging alternative to legacy PFAS. It is therefore evident that even at low concentrations and with short exposure, PFAS can have subtle yet significant effects on behaviour, fertility, and immunity. These findings underscore the potential ramifications of pollution under natural conditions and their impact on fish populations.

Behavioural consequences of intraspecific variability in a mate recognition signal

Mate recognition is paramount for sexually reproducing animals, and many insects rely on cuticular hydrocarbons (CHCs) for close-range sexual communication. To ensure reliable mate recognition, intraspecific sex pheromone variability should be low. However, CHCs can be influenced by several factors, with the resulting variability potentially impacting sexual communication. While intraspecific CHC variability is a common phenomenon, the consequences thereof for mate recognition remain largely unknown. We investigated the effect of CHC variability on male responses in a parasitoid wasp showing a clear-cut within-population CHC polymorphism (three distinct female chemotypes, one thereof similar to male profiles). Males clearly discriminated between female and male CHCs, but not between female chemotypes in no-choice assays. When given a choice, a preference hierarchy emerged. Interestingly, the most attractive chemotype was the one most similar to male profiles. Mixtures of female CHCs were as attractive as chemotype-pure ones, while a female-male mixture negatively impacted male responses, indicating assessment of the entire, complex CHC profile composition. Our study reveals that the evaluation of CHC profiles can be strict towards 'undesirable' features, but simultaneously tolerant enough to cover a range of variants. This reconciles reliable mate recognition with naturally occurring variability.

Effects of past mating behavior versus past ejaculation on male mate choice and male attractiveness

Past reproductive effort allows males to assess their ability to acquire mates, but it also consumes resources that can reduce their future competitive ability. Few studies have examined how a male's reproductive history affects his subsequent mate choice, and, to date, no study has determined the relative contribution of past mating behavior and past ejaculate production because these two forms of investment are naturally highly correlated. Here, we disentangled the relative effects of past mating behavior and past ejaculate production in mosquitofish (Gambusia holbrooki) by experimentally preventing some males from ejaculating when trying to mate. We assessed the effect of mating behavior on mate choice by comparing males that had previously been with or without access to females and male rivals for 8 and 16 weeks and assessed the effect of ejaculation on mate choice by comparing males that either could or could not ejaculate when they had access to females for 16 weeks. Reproductive treatment did not affect male attractiveness, but it did affect male mate choice. Somewhat surprisingly, in five of the six treatment-by-age at testing combinations, males preferred a female in the vicinity of a male rival over a solitary female. This preference was marginally stronger for males that had previously engaged in mating behavior but were unaffected by past ejaculate production. We discuss the potential benefits to males of associating with another male when seeking mates. This is the first study to quantify the relative influence of pre- and post-copulatory reproductive investment on male mate choice.

No geographical differences in male mate choice in a widespread fish, Limia perugiae

Behavior, like most other traits, can have a spatial component, and variability of behavior at the population level is predicted. In this article, we explore male mate choice at this level. Male mate choice, while maybe not as common as female choice, is expected to evolve when males respond to significant variation in female quality and, for example, prefer females with higher fecundity. In fishes, higher fecundity is associated with larger body size, an easily measured trait. In this study, we investigated the presence of male mate choice for larger females in a widespread species of livebearing fish, Limia perugiae, while comparing preferences between populations. We hypothesized that environmental variation, for example, in the form of salinity, might result in population differences. Using dichotomous choice tests, we analyzed behavioral data for 80 individuals from 7 distinct populations from Hispaniola. We found that L. perugiae males significantly preferred large females, but there was no significant statistical variation between populations.

Neural mechanisms involved in female mate choice in invertebrates

Mate choice is a critical decision with direct implications for fitness. Although it has been recognized for over 150 years, our understanding of its underlying mechanisms is still limited. Most studies on mate choice focus on the evolutionary causes of behavior, with less attention given to the physiological and molecular mechanisms involved. This is especially true for invertebrates, where research on mate choice has largely focused on male behavior. This review summarizes the current state of knowledge on the neural, molecular and neurohormonal mechanisms of female choice in invertebrates, including behaviors before, during, and after copulation. We identify areas of research that have not been extensively explored in invertebrates, suggesting potential directions for future investigation. We hope that this review will stimulate further research in this area.

Meta-analytical evidence that males prefer virgin females

Males are often predicted to prefer virgin over non-virgin females because of the reduced risk of sperm competition. Does this prediction hold across studies? Our systematic meta-analysis of 138 studies, mainly conducted in invertebrates, confirms that males generally prefer virgin females. However, males preferred virgin females even in species with last male sperm precedence, suggesting that sperm competition alone does not drive male preferences. Furthermore, our results suggest that males may reject mated females even when no alternative exists. Preference for virgins is unlikely to influence female reproductive success since virginity cannot be selected for, but strong preference for virgin females could swamp or reinforce selection on other traits. Our results add to growing evidence that males are not indiscriminate in mating. However, given the unexplained heterogeneity in effect sizes, we urge caution in assuming that males will prefer virgins and recommend considering the natural context of mating decisions.

The neuropeptide drosulfakinin enhances choosiness and protects males from the aging effects of social perception

The motivation to reproduce is a potent natural drive, and the social behaviors that induce it can severely impact animal health and lifespan. Indeed, in Drosophila males, accelerated aging associated with reproduction arises not from the physical act of courtship or copulation but instead from the motivational drive to court and mate. To better understand the mechanisms underlying social effects on aging, we studied male choosiness for mates. We found that increased activity of insulin-producing cells (IPCs) of the fly brain potentiated choosiness without consistently affecting courtship activity. Surprisingly, this effect was not caused by insulins themselves, but instead by drosulfakinin (DSK), another neuropeptide produced in a subset of the IPCs, acting through one of the two DSK receptors, CCKLR-17D1. Activation of Dsk+ IPC neurons also decreased food consumption, while activation of Dsk+ neurons outside of IPCs affected neither choosiness nor feeding, suggesting an overlap between Dsk+neurons modulating choosiness and those influencing satiety. Broader activation of Dsk+ neurons (both within and outside of the IPCs) was required to rescue the detrimental effect of female pheromone exposure on male lifespan, as was the function of both DSK receptors. The same broad set of Dsk+ neurons was found to reinforce normally aversive feeding interactions, but only after exposure to female pheromones, suggesting that perception of the opposite sex gates rewarding properties of these neurons. We speculate that broad Dsk+ neuron activation is associated with states of satiety and social experience, which under stressful conditions is rewarding and beneficial for lifespan.

Bonding against the odds: Male prairie vole response to the "widow effect" among females

Although pair bonding is the preferred mating tactic among socially monogamous prairie voles, naturalistic observations have demonstrated many males remain non-bonded. Moreover, although males readily re-bond after the loss of a partner, females do not (i.e., the "widow effect'). Few studies have attempted to address why so many males remain non-bonded or if a reluctance of re-bonding in females contributes to this outcome. We investigate how female bonding history impacts male pair bond formation. Specifically, we test two alternative hypotheses for how sexually naïve males will behave when paired with widow females. The fecundity hypothesis predicts males will avoid bonding with widow females and be more receptive to novel bond-naïve females. The preference to bond hypothesis predicts males will choose to bond and express a partner preference, irrespective of if a pair-mate is a widow or sexually naïve. Our results demonstrated that males expressed a partner preference for females regardless of their social history. These data support the preference to bond hypothesis and suggest natural variation in bonding may not be strongly due to males forgoing bonding opportunities.

Multivariate Models of Animal Sex: Breaking Binaries Leads to a Better Understanding of Ecology and Evolution

"Sex" is often used to describe a suite of phenotypic and genotypic traits of an organism related to reproduction. However, these traits-gamete type, chromosomal inheritance, physiology, morphology, behavior, etc.-are not necessarily coupled, and the rhetorical collapse of variation into a single term elides much of the complexity inherent in sexual phenotypes. We argue that consideration of "sex" as a constructed category operating at multiple biological levels opens up new avenues for inquiry in our study of biological variation. We apply this framework to three case studies that illustrate the diversity of sex variation, from decoupling sexual phenotypes to the evolutionary and ecological consequences of intrasexual polymorphisms. We argue that instead of assuming binary sex in these systems, some may be better categorized as multivariate and nonbinary. Finally, we conduct a meta-analysis of terms used to describe diversity in sexual phenotypes in the scientific literature to highlight how a multivariate model of sex can clarify, rather than cloud, studies of sexual diversity within and across species. We argue that such an expanded framework of "sex" better equips us to understand evolutionary processes, and that as biologists, it is incumbent upon us to push back against misunderstandings of the biology of sexual phenotypes that enact harm on marginalized communities.

Mate Discrimination Using Chemical Cues by Male Guppies

Males often perform mate choice with the aim of maximizing reproductive success. To identify profitable mates, the males of some animals are known to use visual and chemical cues derived from females. In this study, we aimed to examine mate discrimination by male guppies (Poecilia reticulata) using chemical cues received from females under different reproductive statuses, i.e., virgin females, pregnant females, females after copulation with another male, and post-partum females. We conducted a dichotomous choice experiment for each combination of chemical stimuli from females under different reproductive statuses. In experiment 1, in which females were removed from water that was subsequently used as a chemical stimulus, male preferences did not differ significantly in all combinations of chemical stimuli from females under different reproductive statuses. However, in experiment 2, in which females remained within bottles containing the water used as a chemical stimulus, with the exception of one combination of chemical stimuli, significant differences in male preferences were detected for chemical stimuli derived from females under different reproductive statuses. Overall, males generally showed a preference for chemical stimulus received from females after copulation with other males. The findings of this study indicate that male guppies can discriminate the reproductive status of females based solely on chemical cues that may disappear or degenerate within a short period of time, thereby facilitating profitable mate choice.

Single fathers sacrifice their broods and re-mate quickly in a socially monogamous cichlid

When one of two parents disappears in the midst of caring for offspring, the remaining parent is left with several options. They can either (1) desert the brood, (2) continue caring on their own and reject propositions from new potential partners, or (3) continue caring but remain receptive to re-mating opportunities. The presence of a brood may increase re-mating success of single parents, either because brood care is perceived as a signal of partner quality, or because prospective mates perceive the brood as potential energy source. In this field experiment, we used the socially monogamous, biparental cichlid fish Variabilichromis moorii to examine the re-mating strategy of males with or without dependent offspring after the loss of their female partner. Partner vacancies were filled quickly by new females, and these females engaged in high levels of affiliative behavior with the males. The new females engaged in territorial defense, but focused primarily against intruding conspecifics, likely as a means to repel rivals. The males, in turn, took over the majority of territorial defense against intruding heterospecifics. Interestingly, males that still had offspring from their previous partnerships did not show aggression toward their new female partners, even when those females were infanticidal and cannibalizing the males' current offspring. Overall, our experiment shows that single fathers of a biparental species will re-mate quickly even at the detriment to their current offspring.

Male size does not affect the strength of male mate choice for high-quality females in Drosophila melanogaster

Theory predicts that the strength of male mate choice should vary depending on male quality when higher-quality males receive greater fitness benefits from being choosy. This pattern extends to differences in male body size, with larger males often having stronger pre- and post-copulatory preferences than smaller males. We sought to determine whether large males and small males differ in the strength (or direction) of their preference for large, high-fecundity females using the fruit fly, Drosophila melanogaster. We measured male courtship preferences and mating duration to show that male body size had no impact on the strength of male mate choice; all males, regardless of their size, had equally strong preferences for large females. To understand the selective pressures shaping male mate choice in males of different sizes, we also measured the fitness benefits associated with preferring large females for both large and small males. Male body size did not affect the benefits that males received: large and small males were equally successful at mating with large females, received the same direct fitness benefits from mating with large females, and showed similar competitive fertilization success with large females. These findings provide insight into why the strength of male mate choice was not affected by male body size in this system. Our study highlights the importance of evaluating the benefits and costs of male mate choice across multiple males to predict when differences in male mate choice should occur.

Sex roles and sex ratios in animals

In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question of why patterns of sex roles vary within and across species remains a key topic in behavioural and evolutionary ecology. New theoretical, experimental and comparative evidence suggests that variation in the adult sex ratio (ASR) is a key driver of variation in sex roles. Here, we first define and discuss the historical emergence of the sex role concept, including recent criticisms and rebuttals. Second, we review the various sex ratios with a focus on ASR, and explore its theoretical links to sex roles. Third, we explore the causes, and especially the consequences, of biased ASRs, focusing on the results of correlational and experimental studies of the effect of ASR variation on mate choice, sexual conflict, parental care and mating systems, social behaviour, hormone physiology and fitness. We present evidence that animals in diverse societies are sensitive to variation in local ASR, even on short timescales, and propose explanations for conflicting results. We conclude with an overview of open questions in this field integrating demography, life history and behaviour.

Evolution of female colours in birds: The role of female cost of reproduction and paternal care

Female ornamentation is frequently observed in animal species and is sometimes found as more evolutionary labile than male ornamentation. A complex array of factors may explain its presence and variation. Here we assessed the role of female cost of reproduction and paternal care. Both factors have been pinpointed as important by theoretical studies but have not been investigated yet in details at the interspecific level. We worked on 133 species of North temperate Passeriformes bird species for which both the clutch volume - here taken as the proxy of female cost of reproduction - and amount of paternal care are relatively well known. Using spectrometry, we measured the whole-body coloured plumage patches and quantified three metrics corresponding to brightness (i.e. achromatic component), colour chromaticity (i.e. intensity) and colour volume (i.e. diversity). We found a strong association between male and female colour metrics. Controlling for this association, we found additional small but detectable effects of both cost of reproduction and paternal care. First, females of species with more paternal care were slightly brighter. Second, the interaction between the level of paternal care and egg volume was correlated with female colour intensity: females with more paternal care were more chromatic, with this association mostly present when their investment in reproduction was low. Together these results suggest that female cost of reproduction and paternal care are part of the multiple factors explaining variation of female coloration, besides the strong covariation between male and female coloration.

Predation risk regulates prey assortative mating by reducing the expected reproductive value of mates

Many animals exhibit size assortative mating (SAM), but how predation affects it remains largely unknown. We hypothesized that predation risk may turn prey less choosy, disrupting SAM, or reduce the expected reproductive value of mates, maintaining SAM but with different size ratio between mates. Using a manipulative field experiment, we found that desert isopods under risk of scorpion predation maintained SAM, but that males that choose and fight over females were on average smaller for a given female size. Less pairs were formed in risky sites, but there were no differences in female sizes and progeny number, size and age near and away from scorpion burrows. Our complementary behavioral experiments revealed that bigger males stayed longer near safe burrows, and won more male-male contests than smaller conspecifics. Our findings highlight that prey can anticipate future costs of predation and use this information to assess the expected reproductive value of mates.

Sexual selection in females and the evolution of polyandry

Over the last decades, the field of sexual selection underwent a paradigm shift from sexual-stereotype thinking of "eager" males and "coy" females towards a more nuanced perspective acknowledging that not only males but also females can benefit from multiple mating and compete for mating partners. Yet, sexual selection in females is still considered a peculiarity, and the evolution of polyandry is often viewed to result from a higher mating interest of males. Here, we present meta-analytic evidence from 77 species across a broad range of animal taxa to demonstrate that female reproductive success is overall positively correlated with mating success, suggesting that females typically benefit from multiple mating. Importantly, we found that these fitness gains likely promote the evolution of polyandry. Our findings offer support for the idea that sexual selection is widespread in females and to play a key role for the evolution of animal mating systems. Thereby, our results extend our understanding of the evolutionary consequences of sexual reproduction and contribute to a more balanced view of how sexual selection operates in males and females.

Asymmetric Male Mating Success in Lek-Breeding Rhinella arenarum

Mate choice is the attempt of an individual to gain higher reproductive fitness by preferring to mate with some individuals and not with others. We studied the role of mate choice in the mating system of the neotropical toad Rhinella arenarum by assessing male reproductive tactics for mate acquisition and the contribution of female choice for pair formation. In a shallow pond in central Argentina, we estimated male mating success and the corresponding reproductive tactics by focal observation. The variation of phenotypic and genotypic traits (size and shape, longevity, vocalization features, heterozygosity) was related to the observed mating success in 110 males. The phonotactic response of 21 reproductive females to conspecific advertisement call features was tested in arena experiments. Mating success was limited to 32 males, pair formation was size-assortative. The dominant reproductive tactics were advertising from call positions near suitable breeding sites and pre-mating fights with intruding males, whereas the interception of amplectant pairs and the displacement of mated males were never observed. Female phonotaxis was directed to conspecific choruses but complex and simple call structures were not distinguished. We conclude that the mating system is a lek combining pre-mating fights among males and female choice of slightly smaller males. Fights interfere with female choice, undermining size-assortative mating. This is a unique system in the R. marina species group, in which interception behavior dominates reproduction.

Hearing, touching, and multisensory integration during mate choice

Mate choice is a potent generator of diversity and a fundamental pillar for sexual selection and evolution. Mate choice is a multistage affair, where complex sensory information and elaborate actions are used to identify, scrutinize, and evaluate potential mating partners. While widely accepted that communication during mate assessment relies on multimodal cues, most studies investigating the mechanisms controlling this fundamental behavior have restricted their focus to the dominant sensory modality used by the species under examination, such as vision in humans and smell in rodents. However, despite their undeniable importance for the initial recognition, attraction, and approach towards a potential mate, other modalities gain relevance as the interaction progresses, amongst which are touch and audition. In this review, we will: (1) focus on recent findings of how touch and audition can contribute to the evaluation and choice of mating partners, and (2) outline our current knowledge regarding the neuronal circuits processing touch and audition (amongst others) in the context of mate choice and ask (3) how these neural circuits are connected to areas that have been studied in the light of multisensory integration.

Male mating preference in an ixodid tick

Background

Mate choice is a fundamental element of sexual selection and has the potential to shape the evolution of traits. Mate choice based on body size has been shown to be a common trait in several arthropod species. In hard ticks, a taxon of medical and veterinary importance, engorgement weight is positively correlated with reproductive output but it is unknown whether adult males show mate choice. Here, we experimentally investigated whether males (i) use chemical cues to choose their mating partner, (ii) consistently choose for the same female individual and (iii) prefer females with highest weight after feeding.

Methods

We used two experimental setups which allowed chemical communication between ticks: (i) a horizontal tube preventing physical contact with the female and (ii) an arena where tactile cues were allowed. In total, we tested 62 different triads in 124 tests (66 tests in the horizontal tube and 58 in the arena) composed of one male that could choose between two engorged females. Specifically, we tested 42 triads in the tube and 46 in the arena; 24 triads were repeatedly tested in the tube while 38 triads were tested in both setups.

Results

We found no preference for individual or heavier females in either setup. However, in the horizontal tube setup, males significantly preferred females that were not visited by them in the previous test.

Conclusions

Our results suggest a lack of male mate choice despite heavier females having higher fecundity. However, future studies should take into account that males may recognize the potential mating partners they previously met.

Graphical Abstract

Assortative mating enhances postzygotic barriers to gene flow via ancestry bundling

Hybridization and subsequent genetic introgression are now known to be common features of the histories of many species, including our own. Following hybridization, selection often purges introgressed DNA genome-wide. While assortative mating can limit hybridization in the first place, it is also known to play an important role in postzygotic selection against hybrids and, thus, the purging of introgressed DNA. However, this role is usually thought of as a direct one: a tendency for mates to be conspecific reduces the sexual fitness of hybrids, reducing the transmission of introgressed ancestry. Here, we explore a second, indirect role of assortative mating as a postzygotic barrier to gene flow. Under assortative mating, parents covary in their ancestry, causing ancestry to be "bundled" in their offspring and later generations. This bundling effect increases ancestry variance in the population, enhancing the efficiency with which postzygotic selection purges introgressed DNA. Using whole-genome simulations, we show that the bundling effect can comprise a substantial portion of mate choice's overall effect as a postzygotic barrier to gene flow. We then derive a simple method for estimating the impact of the bundling effect from standard metrics of assortative mating. Applying this method to data from a diverse set of hybrid zones, we find that the bundling effect increases the purging of introgressed DNA by between 1.2-fold (in a baboon system with weak assortative mating) and 14-fold (in a swordtail system with strong assortative mating). Thus, assortative mating's bundling effect contributes substantially to the genetic isolation of species.

Risky business: males choose more receptive adults over safer subadults in a cannibalistic spider

Understanding factors affecting male mate choice can be important for tracking the dynamics of sexual selection in nature. Male brown widow spiders (Latrodectus geometricus) mate with adult as well as immature (subadult) females. Mating with adults involves costly courtship with a repertoire of signaling behaviors, and typically ends with cannibalism ("self-sacrifice" initiated by male somersault). Mating with subadults involves brief courtship with behavioral repertoire reduced to one component (vibration) and no cannibalism. We examined male mate choice as a function of risks associated with different types of mates and the cues available to courting males. Previous studies showed male preference for adults based on air-borne pheromones, but it was unclear whether that preference is maintained after males reach female's webs. We show that males prefer adults also based on silk-borne contact cues. To determine which types of cues trigger different courtship components, we swapped adults and subadults between webs. We showed that contact with adult females' webs triggers two courtship behaviors from the repertoire, with adult female's bodies triggering additional behaviors. However, vibrational signals occur regardless of the web origin or female developmental stage. We conclude that males recognize subadult females as potential mates, but are more likely to invest in costly courtship behaviors and mating attempts with adults. In our experiments, subadults were less likely to mate than adults. We conclude that mating with adults could be the preferred option for males because of the higher likelihood of copulation, even at the cost of a higher risk of cannibalism.

Larger is not better: no mate preference by European common frog (Rana temporaria) males

In explosive breeding frogs, high intrasexual competition between males leads to a sexual coercion ruled mating system, where males presumably evolved preferences for specific female traits. We tested these preferences in the European Common Frog by excluding intrasexual competition. We hypothesized that all males show preferences towards larger female body size, due to higher fecundity. Our results did not show any preference considering female body size, neither in the attempt to amplex a female nor during the formation of pairs. Additionally, we witnessed a high failure rate of male mating attempts, which hints at high mating costs and offers an explanation for the lack of preferences in males. Nonetheless, we observed a non-random mating pattern in successfully formed pairs, where in the absence of size dimorphism females were on average larger than males. This indicates a different mechanism for selection which is independent from male mating preference or scramble competition.

Sex Differences in Mate Choice Preference Characteristics of Aequidens rivulatus

Simple Summary

Generally, animals prefer mating with partners of the opposite sex with specific features, which suggests that animals tend to choose mates with particular phenotypic traits. However, there are some differences in mate choice behavior and criteria between males and females. This study analyzed these differences between males and females in Aequidens rivulatus by quantifying body size, behavioral intention, and appearance. The results showed that males paid more attention to preference degree and female attractiveness, whereas females focused on ability and physical strength displays. Consequently, males who chose to mate were primarily associated with body size, behavioral intention, and appearance, whereas the preferences of females were body size, appearance, and behavioral intention. Collectively, our initial findings revealed that males and females have different criteria for mate choice, which is vital in determining successful mating and improving artificial mating.

Abstract

The mating roles of males and females, to a certain extent, are dynamic and variable. Several factors influence the mate choice process. Nonetheless, the main preference features have not yet been fully understood in Aequidens rivulatus. In this study, because of its natural pairing characteristics, A. rivulatus was selected to explore the mate choice preferences of different sexes. Specifically, male and female behavioral performances were described and quantified through a “no-choice paradigm” during mate choice. A total of 12 behavioral performances were defined in male mate choice (experiment 1), whereas 14 behavioral performances were defined in female mate choice (experiment 2). According to the obtained results, unselected females did not display any proactive behaviors in experiment 1, whereas unselected males exhibited proactive behaviors in experiment 2, including quivering, nipping, tail beating, swimming up and down, and aggression. It was also found that both male and female individuals tend to express dislike rather than like. Those behaviors with higher frequencies (e.g., quivering) often mean less energy expenditure, thus easier repeatability. Moreover, principal component analysis (PCA) was employed to extract and identify mate choice preference features. Preliminary results indicated that male preferences for a mate were mainly associated with body size, behavioral intention, and appearance, whereas the intensity of female preferences was in the order of body size, appearance, and behavioral intention. In addition, sex hormone levels were associated with mate choices.

Drosophila females have an acoustic preference for symmetric males

Theoretically, symmetry in bilateral animals is subject to sexual selection, since it can serve as a proxy for genetic quality of competing mates during mate choice. Here, we report female preference for symmetric males in Drosophila, using a mate-choice paradigm where males with environmentally or genetically induced wing asymmetry were competed. Analysis of courtship songs revealed that males with asymmetric wings produced songs with asymmetric features that served as acoustic cues, facilitating this female preference. Females experimentally evolved in the absence of mate choice lost this preference for symmetry, suggesting that it is maintained by sexual selection.

In many species, including humans and Drosophila, symmetric individuals secure more matings, suggesting that bilateral symmetry signals the quality of potential mates and is subject to sexual selection. However, this idea remains controversial, largely because obtaining conclusive experimental evidence has been hindered by confounding effects arising from the methods used to increase asymmetry in test subjects. Here, we show that altering gravity during development increases asymmetry in Drosophila melanogaster without a detrimental effect on survival, growth, and behavior. Testing males with altered-gravity–induced asymmetry in female mate-choice assays revealed symmetry-based discrimination of males via auditory cues. Females similarly discriminated against males with genetically induced asymmetry, suggesting that their preference for symmetry is not specific to altered gravity. By segmenting the male courtship song into left and right wing-generated song-bouts, we detected asymmetry in the courtship song of altered-gravity males with asymmetric wings that experienced rejection. Females experimentally evolved in the absence of mate choice lacked this preference for symmetry, suggesting that symmetry is maintained by sexual selection. Our data provide evidence for the role of symmetry in sexual selection and reveal how nonvisual cues can flag mate asymmetry during courtship.

The better, the choosier: A meta-analysis on interindividual variation of male mate choice

Male mate choice occurs in several animal species, but we know little about the factors that influence the expression of this behaviour. Males vary in their capacity to acquire mates (i.e. male quality), which could be crucial to male mate choice expression but it is often overlooked. Using a meta‐analytical approach, we explore interindividual variation in the expression of male mate choice by comparing the mating investment of males of different qualities and phenotypes to high‐ and low‐quality females. We used two datasets that together contained information from 60 empirical studies, comprising 52 species. We found that males of all qualities and phenotypes prefer high‐quality females, but differ in the strength of such preference. High‐ and medium‐quality males are choosier than low‐quality males. Similarly, males that are larger or in greater body condition are choosier than their counterparts. In contrast, male body mass and age are not associated with changes in male mate choice. We also show that experimental design may influence our understanding of male mating investment patterns, which may limit the generalisation of our findings. Nonetheless, we argue that male quality may be an important feature in the expression of male mate choice.

Sex-specific aging in animals: Perspective and future directions

Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age-associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer-lived females, species where males live longer, and species lacking sex differences in lifespan. The underlying causes of sex differences in aging remain mostly unknown. Currently, we do not understand the molecular drivers of sex differences in aging, or whether they are related to the accepted hallmarks or pillars of aging or linked to other well-characterized processes. In particular, understanding the role of sex-determination mechanisms and sex differences in aging is relatively understudied. Here, we take a comparative, interdisciplinary approach to explore various hypotheses about how sex differences in aging arise. We discuss genomic, morphological, and environmental differences between the sexes and how these relate to sex differences in aging. Finally, we present some suggestions for future research in this area and provide recommendations for promising experimental designs.

Behavioral and Evolutionary Perspectives on Visual Lateralization in Mating Birds: A Short Systematic Review

The division of cognitive processing between the two hemispheres of the brain causes lateralized eye use in various behavioral contexts. Generally, visual lateralization is shared among vertebrates to a greater extent, with little interspecific variation. However, previous studies on the visual lateralization in mating birds have shown surprising heterogeneity. Therefore, this systematic review paper summarized and analyzed them using phylogenetic comparative methods. The review aimed to elucidate why some species used their left eye and others their right to fixate on individuals of the opposite sex, such as mating partners or prospective mates. It was found that passerine and non-passerine species showed opposite eye use for mating, which could have stemmed from the difference in altricial vs. precocial development. However, due to the limited availability of species data, it was impossible to determine whether the passerine group or altricial development was the primary factor. Additionally, unclear visual lateralization was found when studies looked at lek mating species and males who performed courtship. These findings are discussed from both evolutionary and behavioral perspectives. Possible directions for future research have been suggested.

Male mate choice in mosquitofish: personality outweighs body size

Background

Despite its important implications in behavioural and evolutionary ecology, male mate choice has been poorly studied, and the relative contribution of personality and morphological traits remains largely unknown. We used standard two-choice mating trials to explore whether two personality traits (i.e., shyness and activity) and/or body size of both sexes affect mate choice in male mosquitofish Gambusia affinis. In the first set of trials involving 40 males, we tested whether males would prefer larger females and whether the preference would be affected by males’ body length and personality traits, and females’ activity level. In the second set of trials (using another 40 males), we tested whether males would prefer more active females and whether the preference would be affected by males’ body length and personality traits.

Results

Both shyness and activity in males were significantly repeatable and constituted a behavioural syndrome. No overall directional preference for large (or small) females with the same activity levels was detected because larger males preferred larger females and smaller males chose smaller females. Males’ strength of preference for larger females was also positively correlated with the activity level of larger females but negatively with the activity level of smaller females. Males spent more time associating with active females regardless of their body lengths, indicating males’ selection was more influenced by female activity level than body size. Males’ preference for inactive females was enhanced when females became active. There was no convincing evidence for the effect of males’ personality traits or body length on their preferences for females’ activity level.

Conclusions

Our study supports the importance of body size in male mate choice but highlights that personality traits may outweigh body size preferences when males choose mating partners.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12983-022-00450-3.

The significant role of post-pairing male behavior on the evolution of male preferences and female traits

Existing sexual selection theory postulates that a sufficiently large variation in female fecundity or other direct benefits are fundamental for generating male mate choice. In this study, we suggest that, in addition to pre-pairing preferences, choosy males can also have different post-pairing behaviors, a factor which has been comparatively overlooked by previous studies. We found that both male preferences and female traits could evolve much more easily than previously expected when the choosy males that paired with unpreferred females would allocate more efforts to seeking additional post-pairing mating opportunities. Furthermore, a costly female trait could evolve when there was a trade-off between seeking additional mating and paternal care investment within social pair for choosy males. Finally, a costly male preference and a costly female trait might still evolve and reach a stable polymorphic state in the population, which might give rise to a high variability in male choice and female traits in nature. We suggest that male mate choice may be even more common than expected, which needs to be verified empirically.

Lyu and colleagues use theoretical models to examine the relationship between post-pairing male behaviors and female trait evolution. They find that male mate choosiness can be surprisingly influential on the evolution of costly female traits, but also that costly male preference and costly female traits could evolve to a polymorphic equilibrium under certain conditions.

Dark-eyed females: sexually dimorphic prespawning coloration results from sex-specific physiological response to hormone exposure in the sand goby Pomatoschistus minutus (Gobiiformes: Gobiidae)

The function and regulation of female nuptial colour signals are poorly understood. In fish, colour is often mediated by chromatophores, allowing for rapid and versatile signalling. Here, we examine a distinct but temporary black line around the eyes and snout (‘dark eyes’) displayed by female sand gobies before spawning and never observed in males. We investigate the regulatory mechanism of the display by analysing the number of melanophores in both sexes in vitro and their response to hormonal exposure. We also test the hypothesis that dark eyes serve an anti-glare function and focus the line of sight, by analysing the frequency, intensity and duration of the display in bright and dim light, with and without males present. We show that the sexes do not differ in terms of the number of melanophores, but that males and females respond in different ways to exposure to melanocyte-stimulating hormone, which has a stronger dilatory effect in females and results in a darker line. However, the darkness of the iris is not affected. Neither light levels nor the presence of potential mates affect the frequency of the dark eye display, but the display is longer lasting and more intense in the presence of smaller nest-holding males.

Sterile males and females can synergistically suppress wild pests targeted by sterile insect technique

The sterile insect technique (SIT) involves periodically releasing artificially sterilized insects to inhibit normal mating between wild insect pests, ultimately resulting in the eradication of wild pest populations. It has often been discussed whether releasing either one sex, mainly males, of sterile insects (i.e., a unisexual release) can enhance the pest-control effect of the SIT more than releasing both sexes (i.e., a bisexual release). We constructed a mathematical model to examine the contribution of sterile males and females to the pest-control effect and the synergy between them. We consider that males seek out and court females in accord with their own female searching ability and preference, and that females subsequently choose one male from among males courting them in accordance with their own preference. Using this model, we compared the pest-control effect of bisexual and unisexual release, focusing on the difference in mating systems of the targeted insects. We showed that for swarm-type mating systems (with few courtship chances with higher encounter rates), bisexual release was the most effective, irrespective of the relative female searching ability between wild and sterile males. In this case, sterile females indirectly reduce wild females mating with either male by absorbing courtship from both wild and sterile males. By contrast, bisexual release is the most effective for scramble-type mating systems (more courtship chances with lower encounter rates) only when the female searching ability of sterile males is lower than that of wild males. In this case, sterile females absorb courtship from males with higher searching abilities. Therefore, the net impact of sterile females depends on the difference in sexual performance between wild and sterile males. Because the sexual performance of sterile insects is often degraded during the process of sterilization, we suggest that bisexual release can be a compatible measure to efficiently suppress wild pest populations.

Does sexual experience affect the strength of male mate choice for high-quality females in Drosophila melanogaster?

Although females are traditionally thought of as the choosy sex, there is increasing evidence in many species that males will preferentially court or mate with certain females over others when given a choice. In the fruit fly, Drosophila melanogaster, males discriminate between potential mating partners based on a number of female traits, including species, mating history, age, and condition. Interestingly, many of these male preferences are affected by the male's previous sexual experiences, such that males increase courtship toward types of females that they have previously mated with and decrease courtship toward types of females that have previously rejected them. D. melanogaster males also show courtship and mating preferences for larger females over smaller females, likely because larger females have higher fecundity. It is unknown, however, whether this preference shows behavioral plasticity based on the male's sexual history as we see for other male preferences. Here, we manipulate the sexual experience of D. melanogaster males and test whether this manipulation has any effect on the strength of male mate choice for large females. We find that sexually inexperienced males have a robust courtship preference for large females that is unaffected by previous experience mating with, or being rejected by, females of differing sizes. Given that female body size is one of the most common targets of male mate choice across insect species, our experiments with D. melanogaster may provide insight into how these preferences develop and evolve.