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Large structural variants in the genome, such as inversions, may play an important role in producing population structure and local adaptation to the environment through suppression of recombination. However, relatively few studies have linked inversions to phenotypic traits that are sexually selected and may play a role in reproductive isolation. Here, we found that geographic differences in the sexually selected plumage of a warbler, the common yellowthroat (Geothlypis trichas), are largely due to differences in the Z (sex) chromosome (males are ZZ), which contains at least one putative inversion spanning 40% (31/77 Mb) of its length. The inversions on the Z chromosome vary dramatically east and west of the Appalachian Mountains, which provides evidence of cryptic population structure within the range of the most widespread eastern subspecies (G. t. trichas). In an eastern (New York) and western (Wisconsin) population of this subspecies, female prefer different male ornaments; larger black facial masks are preferred in Wisconsin and larger yellow breasts are preferred in New York. The putative inversion also contains genes related to vision, which could influence mating preferences. Thus, structural variants on the Z chromosome are associated with geographic differences in male ornaments and female choice, which may provide a mechanism for maintaining different patterns of sexual selection in spite of gene flow between populations of the same subspecies. [ABSTRACT FROM AUTHOR]

Sexual selection is an important evolutionary force and despite extensive research, understanding mate choice on naturally occurring trait variation remains an intriguing area of study. The correlation between mass, a trait associated with courter viability and common target for mate choice, and signals is particularly noteworthy. This study focuses on Schizocosa mccooki, the largest member of a wolf spider genus renowned for its diverse complex male courtship. Our objective was to understand the relationship of male mass and other courtship signals on female choice within this species. We conducted lab experiments involving random pairings of field caught males and females, recording vibratory courtship and its outcomes. Our findings revealed that S. mccooki courtship consisted of vibratory signals with two major components, thumps and raps. Male mass, overall courtship vigor, and thump duration were found to predict mating success. Interestingly, we found no correlation between temporal traits and mass suggesting independent information and an absence of trade‐offs between mass, courtship vigor, and signal component rates/durations. Instead, we found that heavier males tend to produce thumps with lower frequencies. The finding that male mass predicts mating success contrasts with patterns observed in other species in this well‐studied genus. By uncovering the mate choice patterns of S. mccooki, this study underscores the importance of comparative studies to understand the ways in which sexual selection drives diversification, even among closely related taxa. [ABSTRACT FROM AUTHOR]

Sexual selection is critical to animal reproduction. Mate choice not only determines an individual’s capacity for reproduction but is also the primary mode of selection in sexual selection. Mate choice behavior relies on social information, and animals can extract useful information (e.g., genetic quality, hormone levels, physiological status, habitat) about potential mates based on morphological and behavioral traits they observe or perceive and can modify their mate choice strategy by detecting and integrating this information. The information conveyed by potential mates is multimodal. This paper synthesizes the effects of several factors, including individual biological characteristics, sensory systems, hormones and genotype on mate choice, demonstrating that mate choice preferences in the traditional sense are generally more favorable for individuals with superior genes and phenotypes. And the paper also explores the limitations of these studies on mate choice and proposes the future major trend of the correlational research in this field. This work will provide helpful information for guiding the subsequent studies of mate choice in animals. [ABSTRACT FROM AUTHOR]

Females' ability to select mates that can fertilize eggs directly impacts their fitness, but the secondary sexual traits that often guide mate choice may not be directly correlated with male fertility. In externally fertilizing species, such as many fish species, chemical cues in ejaculates may allow females to assess male fertilization capacity. However, chemical cues associated with sperm release have only been described in a few species, and evidence that females use these cues to discriminate among males remains limited. Female sea lamprey, Petromyzon marinus , use several chemical cues to find and interact with potential mates, including a sex pheromone released by males across their gill epithelia and a second sex pheromone released in their semen. Unlike males of many fish species that control pheromone release via urinary pulses, male sea lamprey continually broadcast the gill pheromone once they are sexually mature. This presents a potentially costly scenario for females because attraction to males that are not actively spawning or that are sperm-depleted likely wastes time and energy. We tested the hypothesis that female sea lamprey use pheromones present in seminal plasma to discriminate among potential mates. In-stream behavioural assays revealed that females (1) preferred seminal plasma + male-conditioned water (containing gill-released pheromones) over male-conditioned water alone, (2) preferred male-conditioned water + 2× seminal plasma over male-conditioned water + 1× seminal plasma and (3) oriented towards seminal plasma over large distances and when no male-conditioned water was applied. Taken together, our results indicate that female sea lamprey use seminal pheromones to find and remain near males with immediate fertilization capacity, thereby reducing the risk of wasting time and energy during their single, reproductive window. Finally, our study highlights the importance of multiple cues in mate choice. • We tested whether seminal pheromones provide cues to female lamprey about male status. • Females discriminated males based on the presence of seminal pheromones. • Females discriminated males based on the concentration of seminal pheromones. • Seminal pheromones are a potent, independent cue in sea lamprey. [ABSTRACT FROM AUTHOR]

To explain how populations with distinct warning signals coexist in close parapatry, we experimentally assessed intrinsic mechanisms acting as reproductive barriers within three poison-frog species from the Peruvian Amazon belonging to a Müllerian mimetic ring (Ranitomeya variabilis, Ranitomeya imitator and Ranitomeya fantastica). We tested the role of prezygotic and postzygotic isolation barriers between phenotypically different ecotypes of each species, using no-choice mating experiments and offspring survival analysis. Our results show that prezygotic mating preference did not occur except for one specific ecotype of R. imitator, and that all three species were able to produce viable inter-population F1 hybrids. However, while R. variabilis and R. imitator hybrids were able to produce viable F2 generations, we found that for R. fantastica, every F1 hybrid males were sterile while females remained fertile. This unexpected result, echoing with Haldane’s rule of speciation, validated phylogenetic studies which tentatively diagnose these populations of R. fantastica as two different species. Our work suggests that postzygotic genetic barriers likely participate in the extraordinary phenotypic diversity observed within Müllerian mimetic Ranitomeya populations, by maintaining species boundaries. [ABSTRACT FROM AUTHOR]

Mate choice is posited to explain the evolution and maintenance of numerous secondary sexual traits, including ornamentation. This study explores the role of ornamentation in the mating success of two sister-species of wolf spider with divergent ornamentation. Mature male Schizocosa crassipalpata lack ornamentation while males of its closest living relative, S. bilineata, express both dark pigmentation and foreleg brushes. Following phenotypic manipulations of foreleg ornamentation - i.e. adding ornamentation in the form of dark pigment to non-ornamented males (S. crassipalpata, Aim 1) and removing ornamentation in varying degrees from highly ornamented males (S. bilineata, Aim 2 - shaving brushes; Aim 3 - shaving brushes and painting over dark pigment in vibration present/absent environments) - we found no evidence that ornamentation alone improves male mating success in either species, regardless of the vibratory signaling environment. In both S. bilineata experiments, however, higher courtship rates resulted in higher mating success, suggesting selection for courtship performance. Furthermore, females were more likely to turn, a presumed receptivity display, in response to males that courted at a higher rate. Also, similar to findings in another relative (S. stridulans), we found indications that ornamentation may function to ease a male's reliance on courtship performance - i.e., at low courtship rates, only ornamented males can secure a mating. Our phenotypic manipulations also influenced courtship behavior in S. bilineata. Shaved males began courting earlier and courted more often over a longer time than intact males, yet ultimately acquired similar matings. This increased courtship effort likely compensated for reduced ornamentation. Finally, the vibratory environment appears crucial for female-male dialogue in S. bilineata, as vibratory absent environments resulted in increased female attacks and decreased male courtship rates. Together, our data suggest that S. crassipalpata females do not possess a preference for ornamentation and that S. bilineata females do not use ornamentation alone in mating decisions. Instead, our results are consistent with a hypothesis that ornamentation in Schizocosa evolved, and is likely maintained, due to its interactions with dynamic movement displays (i.e. leg movements), which can themselves be plastically altered based on the signaler's phenotype as well as the signaling environment. [ABSTRACT FROM AUTHOR]

Social animals need to keep track of other individuals in their group to be able to adjust their behaviour accordingly and facilitate group cohesion. This recognition ability varies across species and is influenced by cognitive capacities such as learning and memory. In reptiles, particularly Squamates (lizards, snakes, and worm lizards), chemical communication is pivotal for territoriality, reproduction, and other social interactions. However, the cognitive processes underlying these social interactions remain understudied. In our study, we examined the ability of male and female Tokay geckos (Gekko gecko) to chemically differentiate familiar and unfamiliar mating partners. Our findings suggest that both sexes can make this distinction, with males responding more to the odour of a familiar mate, and females responding more to unfamiliar mates. The lizards maintained their discriminatory abilities for two to three weeks but not up to six weeks after separation. This research highlights the efficacy of using odours as social stimuli for investigating social cognition in lizards, a promising avenue to better understand social cognition in these animals. [ABSTRACT FROM AUTHOR]

Many animals display numerous colors that can range from red, green, blue, and orange to ultraviolet, whereas others are dull or have a uniform coloration. The reason for this variation in coloration remains unknown. It has been hypothesized that different colors represent multiple signals that either reflect different components, redundant information, or simply no longer provide reliable information regarding body quality. Here, we analyzed the highly diverse coloration of male golden pheasants (Chrysolophus pictus) using an avian visual model from the avian visual system and related the different components of coloration to several phenotypic traits of body quality. We found that different components of plumage color correlated with the length of the body, tail, spur, and beak, suggesting that the multiple colors in male golden pheasants signal different components of body quality. In particular, tail length was correlated with many aspects of coloration, especially the green and orange colors of neck plumage, which are particularly important because male golden pheasants spread their neck plumage and show it to females during their courtship display. Therefore, these findings reveal that the plumage colors of male golden pheasants encode multiple signals that reflect their body condition during courtship displays. [ABSTRACT FROM AUTHOR]

How colour polymorphisms are maintained in natural populations constitutes a key subject of study for evolutionary ecologists. One of the mechanisms that has been put forward to explain this phenomenon is negative frequency-dependent selection, which can be caused by different mechanisms. Among these mechanisms is mate choice, or the selection as a potential mate of the rare or dissimilar colour morph by the choosy sex of a given species. In the context of colour polymorphism, mate choice predicts the occurrence of a negative assortative mating pattern, whereby different colour morphs mate more often than expected by chance alone. However, negative assortative mating can also result from other mechanisms, making it, at best, a fallible indicator of a mate choice-driven negative frequency-dependent selection. For this reason, experimental evidence explicitly connecting such a mating pattern to mate choice is necessary to claim that a particular colour polymorphism is being maintained by negative frequency-dependent selection. Here we present experimental evidence backing this relationship for the colour polymorphic marine gastropod Littorina saxatilis from the Ría de Vigo (NW Iberian Peninsula), although how specifically these organisms choose their mates remains unclear. This calls for further experimental efforts to clarify this issue and its relationship to the maintenance of colour polymorphism in L. saxatilis. [ABSTRACT FROM AUTHOR]

ABSTRACT Chemical pollutants and/or climate change have the potential to break down reproductive barriers between species and facilitate hybridization. Hybrid zones may arise in response to environmental gradients and secondary contact between formerly allopatric populations, or due to the introduction of non‐native species. In freshwater ecosystems, field observations indicate that changes in water quality and chemistry, due to pollution and climate change, are correlated with an increased frequency of hybridization. Physical and chemical disturbances of water quality can alter the sensory environment, thereby affecting chemical and visual communication among fish. Moreover, multiple chemical compounds (e.g. pharmaceuticals, metals, pesticides, and industrial contaminants) may impair fish physiology, potentially affecting phenotypic traits relevant for mate selection (e.g. pheromone production, courtship, and coloration). Although warming waters have led to documented range shifts, and chemical pollution is ubiquitous in freshwater ecosystems, few studies have tested hypotheses about how these stressors may facilitate hybridization and what this means for biodiversity and species conservation. Through a systematic literature review across disciplines (i.e. ecotoxicology and evolutionary biology), we evaluate the biological interactions, toxic mechanisms, and roles of physical and chemical environmental stressors (i.e. chemical pollution and climate change) in disrupting mate preferences and inducing interspecific hybridization in freshwater fish. Our study indicates that climate change‐driven changes in water quality and chemical pollution may impact visual and chemical communication crucial for mate choice and thus could facilitate hybridization among fishes in freshwater ecosystems. To inform future studies and conservation management, we emphasize the importance of further research to identify the chemical and physical stressors affecting mate choice, understand the mechanisms behind these interactions, determine the concentrations at which they occur, and assess their impact on individuals, populations, species, and biological diversity in the Anthropocene. [ABSTRACT FROM AUTHOR]

The role of hybridization as a formative process in evolution has received much attention in the past few decades. A particularly fascinating outcome of hybrid speciation is the formation of asexual hybrid species. The Amazon molly (Poecilia formosa) is such a hybrid and originated from a P. mexicana mother and a P. latipinna father. Consequently, a heterospecific mating must have occurred leading to the Amazon molly, indicating a breakdown of any potential prezygotic isolation between parental species. Here we studied the female mate preferences of extant P. mexicana and P. latipinna from several populations using standard binary choice tests with males of both sexual species that were matched for size. Poecilia mexicana and P. latipinna can be crossed in the lab, however, the offspring are not asexual, but sexual F1s. In our study, we generated F1s and tested their mating preferences with sexual males of both P. mexicana and P. latipinna against F1 males. Overall, our results show that in extant P. mexicana and P. latipinna no female preference for conspecific males was detectable. Consequently, heterospecific matings are possible and not hindered by any apparent behavioral prezygotic isolation. If female preferences in these species were comparable around the time the Amazon molly originated as a hybrid species ca. 100,000 years ago, matings leading to hybrids would be very likely. F1 females also have no discernable mating preferences for either sexual males or F1 males. Such lack of prezygotic behavioral isolation could potentially lead to F2 individuals, backcrosses, and introgression. [ABSTRACT FROM AUTHOR]

The way people create social connections and access information has been altered greatly by technology in recent decades. Online browsing of visual profiles has become a common means for seeking potential partners for both short- and long-term relationships. Little is known, however, about how people prioritize mate quality information while viewing online profiles. Using eye-tracking methods and self-report, this study investigated how people evaluated profile-based facial attractiveness and text-based financial resources information, represented by income and occupation. Heterosexual male and female participants, aged between 18 and 27 years, viewed opposite-sex profiles while their eye-movements were recorded using a remote eye-tracking camera. In line with current theory, resources information had little effect on men's overall attention to women's faces, whereas women's overall attention to men's faces varied depending on the level of income and occupation. Women evaluated men's faces more when income and occupation were low, regardless of attractiveness. Unexpectedly, however, men marginally increased their attention toward unattractive women who showed a high-level of income and more esteemed occupation. Men self-reported a higher interest in women for a short-term relationship and women self-reported a higher interest in men for a long-term relationship. This work provides a foundation to further examine how people browse profile-based information and to investigate the mate selection process, with real-world implications for online dating app users, profile design, and content. [ABSTRACT FROM AUTHOR]

Heterosexual men and women who report more than the average number of sexual partners also report greater exposure to interpersonal violence and substance use. This relationship is less well-understood in sexual minorities (e.g., gay, lesbian, and bisexual). In the current study, data from 12,407 participants from four waves of the National Longitudinal Study of Adolescent to Adult Health were examined. Psychological and sociological risk factors were controlled for in the analyses which included self-control, religiosity, depression, marital and cohabiting status, educational attainment, and employment. While exceptions are noted, the results overall lend support to the hypothesis that relationships with the opposite sex carry a greater risk of exposure to violence and substance use than do same-sex relationships. This was the case for heterosexual men and women, and also held true within some groups of sexual minorities. Among hetero and mostly heterosexual men, competition for women was found to be especially risky for violence perpetration, perhaps because the likely rivals would include other heterosexual men. The significant effects of same-sex partners were largely limited to women but were also significant and negative for heterosexual men's drug use. Mostly heterosexual and bisexual individuals were found to have experienced more violence/victimization, used more drugs, and drank to the point of getting drunk more often (on average) than other sexual minorities. Controlling for psychological and sociological risk factors did not explain the effects of sexual orientation or sexual experience. Limitations and directions for future research are discussed. [ABSTRACT FROM AUTHOR]

Background: Consistent across cultures and throughout time is the male preference for younger females. Given its prevalence, the mate choice theory proposes that age–disparate relationships may have contributed to the evolution of maternal mortality and menopause. Objectives: The objective is to document evidence for age disparity in marriage from past and present populations and evaluate their relevance to maternal mortality and menopause. Design: Cross-sectional data were collected from various regions and time points, ranging from the Roman era to the current decade. Methods: To analyze both the age disparity in marriage and age at marriage, data were collected from Ancestry.ca for Quebec, Massachusetts, India, South Africa, and England and Wales. Additional data were taken from the United Nations as a more recent and comprehensive source. To analyze the relationships between age disparity in marriage and different social factors, data on gross domestic product, maternal mortality rates, fertility, primary school enrollment, child marriage rates, and percentage of women in the total labor force were collected from the World Health Organization, World Bank, and United Nations International Children's Emergency Fund. Results: The results showed that males were significantly older than females at first marriage in all populations and time frames sampled, supporting the assumption underlying the mate choice theory. Maternal mortality rates were strongly associated with age–disparate relationships, increasing by 275 per 100,000 live births for each additional year in the age disparity. Conclusion: The results from this study provide support for the assumption underlying the mate choice theory of maternal mortality and menopause. Plain language summary: Changing patterns of global age disparity in marriage provide support for the mate choice theory of menopause, raising the possibility of a gradual shift in delayed reproduction and delayed menopause. Living things have inherent capacity to survive and reproduce until they die, with one exception: humans. Women go through menopause while men remain fertile. Among the many explanations offered for the origin of menopause, grandmother hypothesis is the leading one. Being too old to reproduce, it is argued, grandmothers stop reproducing and make up for the loss of fitness through helping (grand mothering) their grand offspring. There are two problems with this theory: first, grand mothering and menopause need not be connected, and second, grandmothers cannot be simultaneously too old to reproduce and not too old to be able to gather resources to make up for their loss of fitness. We proposed a mate choice theory of menopause which posits that human mating system is non-random, that is, males have preference for younger females, depriving older females from reproduction and allowing deleterious fertility mutations to accumulate giving rise to menopause. Male preference for younger females is consistent across cultures and dominates all social relations affecting mate choice including monogamy, serial monogamy, widowers remarrying, polygamy, harem, and others. In this study, we wanted to test if male preference for younger females has been widespread through time. We collected data on age disparity in marriage from past and present populations, from Roman era to the current decade, and evaluated their relevance to the origin of maternal mortality and menopause. The results showed that males were significantly older than females at first marriage in all populations and time frames sampled, supporting the assumption underlying the mate choice theory of menopause. Maternal mortality rates were strongly associated with age–disparate relationships, increasing by 275 per 100,000 live births for each additional year in the age disparity. Through repeated cycles of widowers marring younger women, maternal mortality would have functioned as a reinforcer of the origin of menopause. [ABSTRACT FROM AUTHOR]

Mate choice plays a fundamental role in speciation, yet we know little about the molecular mechanisms that underpin this crucial decision-making process. Stickleback fish differentially adapted to limnetic and benthic habitats are reproductively isolated and females of each species use different male traits to evaluate prospective partners and reject heterospecific males. Here, we integrate behavioural data from a mate choice experiment with gene expression profiles from the brains of females actively deciding whether to mate. We find substantial gene expression variation between limnetic and benthic females, regardless of behavioural context, suggesting general divergence in constitutive gene expression patterns, corresponding to their genetic differentiation. Intriguingly, female gene co-expression modules covary with male display traits but in opposing directions for sympatric populations of the two species, suggesting male displays elicit a dynamic neurogenomic response that reflects known differences in female preferences. Furthermore, we confirm the role of numerous candidate genes previously implicated in female mate choice in other species, suggesting evolutionary tinkering with these conserved molecular processes to generate divergent mate preferences. Taken together, our study adds important new insights to our understanding of the molecular processes underlying female decision-making critical for generating sexual isolation and speciation. [ABSTRACT FROM AUTHOR]

ABSTRACT Sexual selection has been a popular subject within evolutionary biology because of its central role in explaining odd and counterintuitive traits observed in nature. Consequently, the literature associated with this field of study became vast. Meta‐analytical studies attempting to draw inferences from this literature have now accumulated, varying in scope and quality, thus calling for a synthesis of these syntheses. We conducted a systematic literature search to create a systematic map with a report appraisal of meta‐analyses on topics associated with sexual selection, aiming to identify the conceptual and methodological gaps in this secondary literature. We also conducted bibliometric analyses to explore whether these gaps are associated with the gender and origin of the authors of these meta‐analyses. We included 152 meta‐analytical studies in our systematic map. We found that most meta‐analyses focused on males and on certain animal groups (e.g. birds), indicating severe sex and taxonomic biases. The topics in these studies varied greatly, from proximate (e.g. relationship of ornaments with other traits) to ultimate questions (e.g. formal estimates of sexual selection strength), although the former were more common. We also observed several common methodological issues in these studies, such as lack of detailed information regarding searches, screening, and analyses, which ultimately impairs the reliability of many of these meta‐analyses. In addition, most of the meta‐analyses' authors were men affiliated to institutions from developed countries, pointing to both gender and geographical authorship biases. Most importantly, we found that certain authorship aspects were associated with conceptual and methodological issues in meta‐analytical studies. Many of our findings might simply reflect patterns in the current state of the primary literature and academia, suggesting that our study can serve as an indicator of issues within the field of sexual selection at large. Based on our findings, we provide both conceptual and analytical recommendations to improve future studies in the field of sexual selection. [ABSTRACT FROM AUTHOR]

Multiple cues are often used for mate choice in complex environments, potentially entailing mismatches in the information conveyed by different sources. We address the consequences of this information mismatch for receivers using the spider mite Tetranychus urticae, in which virgin females are highly valuable mates compared to mated females, given first male sperm precedence. Accordingly, males are known to prefer virgins and distinguish them using cues from the females themselves and that they leave on the substrate. Whereas cues from females are highly reliable, those left on the substrate may not reflect the real female mating status if females move and/or mate. Here, we tested the consequences of such mismatch by exposing males to mated or virgin females on patches previously impregnated with cues deposited by females of either mating status. Male mating attempts were solely affected by substrate cues while female acceptance and the number of mating events were independently affected by both cues. Copulation duration, in contrast, depended mainly on the mating status of the female, with the number of copulations and the total time spent mating being intermediate in environments with mismatched information. We also show that males incur mating costs, reflected in reduced survival in environments with virgin cues. These results suggest that substrate cues left by females are instrumental for males to find their mates. However, in environments with mismatched information, males may pay survival costs without the associated benefit of mating with virgins, or they may lose opportunities to mate with virgins by responding to substrate cues from mated females. The benefit of using multiple cues will then hinge upon the frequency of information mismatch, which itself should vary with the dynamics of populations. [ABSTRACT FROM AUTHOR]

The ecological stage of mating interactions has crucial implications for trait divergence and speciation; the novel environments created by humans can undermine the speciation process. Sexually selected traits and the fitness benefits of mating interactions are often finely attuned to the environments in which they evolved; anthropogenic change alters signal–receiver dynamics and mating decisions, thereby often increasing hybridization. Hybridization can undermine biodiversity. Occasionally it can have a creative function by increasing potentially adaptive genetic diversity, allowing for adaptive introgression, or enhancing mating trait evolution. Yet, these outcomes are uncertain and may not fully compensate for biodiversity loss. We inject a much-needed global change perspective for understanding sexual selection as a driver of the speciation process in a rapidly changing world. Anthropogenic change threatens global biodiversity by causing severe ecological disturbance and extinction. Here, we consider the effects of anthropogenic change on one process that generates biodiversity. Sexual selection (a potent evolutionary force and driver of speciation) is highly sensitive to the environment and, thus, vulnerable to anthropogenic ecological change. Anthropogenic alterations to sexual display and mate preference can make it harder to distinguish between conspecific and heterospecific mates or can weaken divergence via sexual selection, leading to higher rates of hybridization and biodiversity loss. Occasionally, anthropogenically altered sexual selection can abet diversification, but this appears less likely than biodiversity loss. In our rapidly changing world, a full understanding of sexual selection and speciation requires a global change perspective. [ABSTRACT FROM AUTHOR]

The efficacy of sexual signals in communication is often maximized under specific environmental conditions. Anthropic alterations of these conditions might, thus, negatively affect communication during reproductive behavior. In fossorial animals, inhabiting visually restricted environments, chemical senses are very important. We examined whether climatic episodes of heat-waves with unusual high temperatures may affect the information provided to females by the sexual chemical signals of males of a fossorial reptile, the amphisbaenian Blanus cinereus. The results showed that experimentally heat-altered substrate scent marks of males can still provide information to females about the presence of a male. Females spent more time on males' scent marks, irrespective of the temperature treatment, than on control clean ones. However, heat-altered scent marks did not seem to convey information about the health state (immune response) of the producer. Females spent more time on unaltered scent marks of healthier males (probably indicating mating preferences for these males), while female preferences for some heat-altered scent marks were not related to size or immune response of the same individual males. Chemical analyses indicated that the overall chemical profile of precloacal secretions (used for scent marking) did not change with increased temperatures. However, the relationship between proportions of some compounds in secretions and males' immune response found in unaltered secretions was lost in heat-altered ones. We conclude that unusual increased environmental temperatures may decrease the efficacy of underground sexual chemical signals in this amphisbaenian (i.e., a loss of information on male quality), and consequently, may negatively affect sexual selection and reproduction. Significance statement: It's crucial to be as successful as possible when you show off to attract a mate. This may depend on how the surroundings affect the effectiveness of your exhibition. So, animals have evolved sexual signals tuned up to their local environmental conditions. A blind fossorial reptile uses substrate scent marks to transmit information to conspecifics. The projected rise in soil temperatures due to climate change could alter this communication. Although brief exposures to high temperatures still allows scent marks to inform females that a male is around, the information related to that male quality is disrupted. This could have detrimental effects on female reproductive success by drastically decreasing their capacity to select a suitable partner. It is unknown if animals could change their sexual signals in order to re-adjust to the rapidly shifting new climatic conditions. [ABSTRACT FROM AUTHOR]

Abstract To explain how populations with distinct warning signals coexist in close parapatry, we experimentally assessed intrinsic mechanisms acting as reproductive barriers within three poison-frog species from the Peruvian Amazon belonging to a Müllerian mimetic ring (Ranitomeya variabilis, Ranitomeya imitator and Ranitomeya fantastica). We tested the role of prezygotic and postzygotic isolation barriers between phenotypically different ecotypes of each species, using no-choice mating experiments and offspring survival analysis. Our results show that prezygotic mating preference did not occur except for one specific ecotype of R. imitator, and that all three species were able to produce viable inter-population F1 hybrids. However, while R. variabilis and R. imitator hybrids were able to produce viable F2 generations, we found that for R. fantastica, every F1 hybrid males were sterile while females remained fertile. This unexpected result, echoing with Haldane’s rule of speciation, validated phylogenetic studies which tentatively diagnose these populations of R. fantastica as two different species. Our work suggests that postzygotic genetic barriers likely participate in the extraordinary phenotypic diversity observed within Müllerian mimetic Ranitomeya populations, by maintaining species boundaries.

Evolutionary changes and interspecific diversity in sexual coercion and autonomy are often linked to indirect selection on mate preferences. Yet, this approach overlooks the small fraction of indirect selection in total selection on mate choice and assumes unnecessarily specific conditions in the recent ‘autonomy-enhancing’ risk-reduction model. This paper proposes a more parsimonious approach based on direct selection and basic signalling theory, incorporating ecological variables to better explain sexual biodiversity. Particularly, the spatial dimensionality of mating environments is emphasized for its role in enhancing sexual freedom through both diminishing monopolization and elevating escape potential from sexual coercion. Empirical evidence, ranging from waterfowl to humans, seems to better align with this ecologically constrained signalling perspective. Furthermore, it suggests that choosers keep coercion risk at ecological baseline by leveraging their escape potential. This repositions intriguing protective elements like bowerbirds' constructions as courtship features that have been bargained to respect sexual autonomy rather than enhancing it through indirect selection. It implies that courtship induced risks, such as reduced mobility, may in principle increase substantially precisely because they are offset by protective measures. Future research could reveal the prevalence of such risk-balancing strategies, advancing our understanding of mating dynamics. This work suggests new theoretical and empirical research avenues within the ecology of mating dynamics. [ABSTRACT FROM AUTHOR]

Choosing a romantic partner for a long-term relationship is one of the most significant decisions one makes during our lifetime. We have inherited an evolved framework from our ancestors that contains traits, as well as preferences for these traits, to solve this task. We use this framework consciously or unconsciously to choose prospective romantic partners. Following this reasoning, sexual strategy theory (SST) has been proposed for predicting which traits women and men prefer in a romantic partner for a long-term relationship. These predictions were empirically tested in the current work based on a sample of 1193 Norwegian adolescents who responded to an online questionnaire. We implemented the study hypotheses, derived from SST, in three statistical models, which were tested using structural equation modeling. In brief, our results revealed that women only valued resources more than men when we controlled for materialistic traits. This finding contrasts with SST's prediction that women would value resources more than men, independently of other variables. As for the second prediction that men value physical attractiveness more than women, this pattern existed universally and was independent of, for instance, how egalitarian they were. We thus conclude that SST was only partially supported and that variables that may reflect societal circumstances (e.g., wealth, gender, equality) should be considered when examining the mate choice behavior of women and men. The theoretical and practical implications of the study are also discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Historically, researchers' biases about male and female behavior have affected the study of mate choice (animals' selective responses to certain sexual partners over others), and female mate choice has often been dismissed as unimportant. In this study, we investigated whether female blue monkeys could exercise mate choice successfully by siring offspring with their preferred males. Blue monkeys generally live in a one-male multi-female social organization, but multiple males may join the group during the breeding season. Female blue monkeys, thus, have access to multiple potential mates, and initiate sexual interactions more than males, making them an appropriate species in which to study female choice. We found that a female's most preferred male was most likely to be the father of her infant, even if he was not a consistent group member. Though competition between males may still influence paternity outcomes, these results suggest that blue monkey females can exercise mate choice successfully, even in a social organization that would seem to favor male control. Female mate choice may drive sexual selection, but discerning whether female behaviors reflect free expression of choice or responses to constraints can be difficult. We investigated the efficacy of female choice in wild blue monkeys using 10 years of behavior and paternity data (N = 178 male–female dyads). Although blue monkeys live modally in one-male polygynous groups, where male-biased intersexual power is expected, females can access multiple potential mates during seasonal male influxes and occasional intergroup encounters. Additionally, extra-group males sire offspring. We examined female resistance rates to male-initiated sexual interactions, and unsolicited proceptive behavior that females directed to males (corrected for male availability). Females seldom resisted male solicitation, but initiated sexual interactions more than males. Females generally preferred residents. Those who preferred non-residents tended to have residents with longer tenures, but neither female parity nor rank influenced the tendency to prefer non-residents vs. residents. The male most solicited by a particular female fathered that female's infant 82% of the time; odds of siring were 26 times higher for most vs. nonpreferred males. Female preference predicted paternity even more strongly among non-resident males, with odds of siring 33 times higher for most vs. nonpreferred non-residents. Neither female rank nor parity influenced her likelihood of having her preferred partner as sire. Paternity by preferred males did not affect infant survival. While we cannot fully discount the effect of male–male competition on paternity, these results suggest that blue monkey females can exercise choice successfully, even in a polygynous mating system. [ABSTRACT FROM AUTHOR]

Human populations harbor a high concentration of deleterious genetic variants. Here, we tested the hypothesis that non-random mating practices affect the distribution of these variants, through exposure in the homozygous state, leading to their purging from the population gene pool. To do so, we produced whole-genome sequencing data for two pairs of Asian populations exhibiting different alliance rules and rates of inbreeding, but with similar effective population sizes. The results show that populations with higher rates of inbred matings do not purge deleterious variants more efficiently. Purging therefore has a low efficiency in human populations, and different mating practices lead to a similar mutational load. [ABSTRACT FROM AUTHOR]

Ploceus philippinus is one of the common weaver birds in the South Karnataka region of India, which is renowned for its distinctive nest-building architecture. The male Baya weaver bird selects the nesting site based on various factors such as microclimate, temperature, light intensity, and the availability of nesting materials and food sources. In the current investigation, it has been observed that how male weaver birds exhibit a deliberate selection process, choosing host plants for nest construction. The male birds participate in the intricate process of nest-making, and the female bird begins to visit the nest. The male birds of the colony make noise and frenetic flights around the nest with excitement when female birds are sighted around the trees. Each male bird elevates their nest toward the female by fluttering his wing and pushes the nest. The female, in turn, meticulously inspects each nest by poking her beak into the wall and pulling out some fiber as if performing a ritualized test of building standards. Ultimately, the nest is selected by the female, which indicates her willingness to accept the nest architect as her mate. The present study illuminates that the key determinant of reproductive success lies in the discerning choice made by the female through the process of mate selection. [ABSTRACT FROM AUTHOR]

Visual and auditory signals are well-established components of avian courtship, but the role of chemical signaling remains poorly understood, particularly in mating systems with elaborate courtship displays. To test how chemical cues influence mating behavior we conducted two experiments in the lance-tailed manakin (Chiroxiphia lanceolata). First, in a field experiment, we tested the response of free-living males and females to manipulation of chemical cues at male display perches by cleaning the perches with ethanol or a dry cloth (control) and quantified a potential chemical signaling behavior (bill-wiping) in response to experimental manipulation. During bouts of dance perch maintenance and displays with a female present (i.e., activity relevant to female mate choice) males increased bill-wiping behavior during initial ethanol treatment periods. We also detected carryover effects of the ethanol treatment; in later treatment periods males bill-wiped more when the prior treatment was ethanol. The likelihood of a female either revisiting a display area or copulating with a male was unrelated to experimental treatment. Next, in captive trials, we assessed female preference for olfactory cues from males that differed in their genetic diversity, a trait previously identified as relevant to female mate choice. In contrast to similar trials in other bird species, females showed no clear preference. Together, these results provide some evidence for chemical signaling by males at display perches, but it remains unclear what information chemical cues convey. Significance statement: Chemical communication is an understudied phenomenon in birds, and especially so when it occurs as part of complex courtship displays. We investigated chemical signaling in the mating behavior of a highly polygynous bird with elaborate courtship displays by experimentally altering the chemical cues at courtship sites that are actively maintained by males. Male lance-tailed manakins detect and respond to changes in the chemical environment on display perches, however we detected no response from females. Our results contrast with other studies that detected significant responses to chemical cues by both males and females and suggest that association time with chemical cues may be important to their detection in avian systems. [ABSTRACT FROM AUTHOR]

Resistance to mating by females has been hypothesized as a tactic to assess potential mates and avoid undesirable ones. Previous studies show infection with the pathogenic bacteria, Pseudomonas aeruginosa, triggers a costly immune response and negatively impacts fitness in the wolf spider Schizocosa ocreata (Hentz 1844). Studies also show that infection can be transmitted during copulation, suggesting that there are potential fitness costs associated with mating with an infected individual. We examined impacts of infection on mating interactions of male and female S. ocreata. As studies show infection can be detected through chemical cues, we tested whether males or females avoid mating with infected individuals when given the opportunity. We paired infected and uninfected (control) males and females and recorded their behavior. We found that mating outcome was independent of infection for males and females. While higher male courtship rates and more frequent female receptivity displays were associated with successful mating, we saw no direct effect of infection status on mating outcome. However, among spider pairs that did not mate, females were found to be significantly more resistant and aggressive toward infected males than control males. Male aggression, on the other hand, was greater in pairs that did result in mating. These results suggest that sexual conflict in mating can be related to infection status, and that females can recognize infected males and alter their behavior in response. [ABSTRACT FROM AUTHOR]

Mating behavior arises from interactions between males and females. The precopulatory stage includes various male and female mating behaviors that are potentially influenced (independently or jointly) by each sex, thereby shaping the dynamics of this stage. However, limited attention has been given to determining the relative contributions of males and females to the expression of precopulatory behaviors. Here, we adopted a variance-partitioning approach to assess which sex controls each precopulatory behavior. This approach also enabled us to evaluate the existence of mate choice by assessing whether the expression of precopulatory behavior depends on the identity of the opposite-sex partner. In our study, using the bean bug Riptortus pedestris , we exposed individual males and females to different opposite-sex partners (i.e. mating assays) up to six times. During the mating assay, we measured multiple precopulatory behaviors (e.g. latency to mount, courtship rate, courtship duration, and duration of position change). Variance partitioning showed that the variation in each precopulatory behavior could be attributed solely to either sex but not to both sexes. Hence, the precopulatory stage of R. pedestris comprises a combination of male-controlled and female-controlled behaviors. We also suggested that mate choice was absent in both sexes of R. pedestris in the postmounting and precopulatory stages. Our findings highlight the importance of the variance-partitioning approach in the study of mating behavior, as it facilitates the investigation of whether mate choice occurs at specific mating stages and enhances our understanding of evolutionary dynamics during mating. [ABSTRACT FROM AUTHOR]

Viability indicator traits are expected to be integrated extensively across the genome yet sex-limited to ensure that any benefits are sexually concordant. Understanding how such expectations are accommodated requires elucidating the quantitative genetic architecture of candidate traits in and across the sexes. Here we applied an animal modelling approach to partition the autosomal, allosomal, and direct maternal bases of variation in sexual versus non-sexual dorsal wing colouration in the butterfly Eurema hecabe. The sexual colour trait—coherently scattered ultraviolet that is under strong directional selection due to female choice—is brighter and more expansive in males, and overlays non-sexual pigmentary yellow markings that otherwise dominate both wing surfaces in each sex. Our modelling estimated high and sexually equivalent autosomal variances for ultraviolet reflectance (furnishing h 2 ~ 0.58 overall and ~0.75 in males), accompanied by smaller but generally significant Z-linked and maternal components. By contrast, variation in non-sexual yellow was largely attributed to Z-linked sources. Intersexual genetic correlations based upon the major source of variation in each trait were high and not different from 1.0, implying regulation by a pool of genes common to each sex. An expansive autosomal basis for ultraviolet is consistent with its hypothesized role as a genome-wide viability indicator and ensures that both sons and daughters will inherit their father's attractiveness. [ABSTRACT FROM AUTHOR]

Female mate choice decisions are guided by preferences for male display features, but in chorusing species the displays of different males may temporally overlap. Here, mate choice decisions may be guided by preferences based on signal timing in addition to signal features. Which type of preference dominates has implications for our understanding of the dynamics of sexual selection in group-displaying animals. I presented female treefrogs with a series of playback treatments varying the amounts of calls in leader/follower position to establish the lowest proportion of leading calls resulting in a preference. About half the females expressed leader preferences when fewer than 15% of calls are in leading position (the maximum produced by chorusing males). This suggests that mate choice decisions will be dominated by call timing preferences in some females, and by call features preferences others, overall lowering the strength of selection on either male display trait. [ABSTRACT FROM AUTHOR]

More than a century ago, Darwin proposed a putative role for music in sexual attraction (i.e., sex appeal), a hypothesis that has recently gained traction in the field of music psychology. In his writings, Darwin particularly emphasized the charming aspects of music. Across a broad range of cultures, music has a profound impact on humans’ feelings, thoughts and behavior. Human mate choice is determined by the interplay of several factors. A number of studies have shown that music and musicality (i.e., the ability to produce and enjoy music) exert a positive influence on the evaluation of potential sexual partners. Here, we critically review the latest empirical literature on how and why music and musicality affect sexual attraction by considering the role of music-induced emotion and arousal in listeners as well as other socio-biological mechanisms. Following a short overview of current theories about the origins of musicality, we present studies that examine the impact of music and musicality on sexual attraction in different social settings. We differentiate between emotion-based influences related to the subjective experience of music as sound and effects associated with perceived musical ability or creativity in a potential partner. By integrating studies using various behavioral methods, we link current research strands that investigate how music influences sexual attraction and suggest promising avenues for future research. [ABSTRACT FROM AUTHOR]

Male chum salmon display a courtship behaviour involving an actively "quivering" against female, which is essential for female orgasm. Because generally male prefer larger female, we determined whether the elements of quivering such as the number, the amplitude, and the distance are affected by female body size. Additionally, quivering changes towards oviposition; therefore, we also identified the essential time for the male to succeed in his courtship behaviour. We conducted two experiments to measure quivering parameters: (i) measuring the number and the amplitude of quivering by the acceleration data logger and (ii) measuring the distance between sexes during quivering by observation of recorded video. From the first experiment, there was no significant relationship between the ratio of female‐to‐male body lengths and the number and the amplitude of quivering, while an important relationship between the body length ratio and the distance between sexes from the second experiment. Therefore, we think the distance is more significant than the number or vigour of quivering for male choice, and males quiver more closely to a larger female to increase reproductive success. In addition, when the body length ratio of the sexes is 1.01, the distance during quivering is the shortest. So, there is a possibility that the reproduction of chum salmon is based on size‐assortative mating. And both experiments also showed that male quiver passively as spawning approaches. We suggest that males may not quiver actively for smooth mating as females spawning approaches. [ABSTRACT FROM AUTHOR]

Theory predicts that males and females of dioecious species typically engage in an evolutionary sexual conflict over the frequency and choice of mating partner. Female sexual cannibalism, a particularly dramatic illustration of this conflict, is widespread in certain animal taxa including spiders. Nevertheless, females of some funnel weaving spiders that are generally aggressive to conspecifics enter a cataleptic state after male courtship, ensuring the males can mate without risk of attack. In this study, we demonstrated that the physical posture and duration, metabolites, and central neurotransmitters of females of Aterigena aculeata in sexual catalepsy closely resemble females in thanatosis but are distinct from those in anesthesia, indicating that the courted females feign death to eliminate the risk of potentially aggressive responses and thereby allow preferred males to mate. Unlike the taxonomically widespread thanatosis, which generally represents a deceptive visual signal that acts against the interest of the receivers, sexual catalepsy of females in the funnel weaving spiders may deliver a sexual-receptive signal to the courting males and thereby benefit both the signal senders and receivers. Therefore, sexual catalepsy in A. aculeata may not reflect a conflict but rather a confluence of interest between the sexes. [ABSTRACT FROM AUTHOR]

Individuals are thought to seek the best possible romantic partner in exchange for their own desirability. We investigated whether individuals' self-evaluations were related to their partner choices and whether the accuracy of these self-evaluations was associated with mating outcomes. Participants (N = 1,354) took part in a speed-dating study where they rated themselves and others on mate value and indicated their willingness to date each potential partner. Individuals were somewhat accurate in their self-evaluations, and these self-evaluations were associated with individuals' revealed minimum and maximum standards for a potential partner, but not the number of partners they were interested in. Participants who overestimated their mate value were accepted by an equivalent number of partners compared with under-estimators, but the over-estimators were choosier and thus ended up with fewer (but similarly attractive) reciprocal matches. Results support social exchange theory and the matching hypothesis, and contrast findings that self-enhancement facilitates positive social outcomes. [ABSTRACT FROM AUTHOR]

Traits that mediate reproductive isolation between species, such as those involved in mate choice and/or recognition, are predicted to experience stabilizing selection towards the species mean. Male orchid bees collect chemical compounds from many sources, such as plants and fungi, which they use as a perfume signal (pheromone) during courtship display, and are suggested to contribute to reproductive isolation between species. Environmentally acquired signals are more prone to variation as source availability can vary through space and time. If orchid bee perfumes are important for reproductive isolation between species, we expect them to exhibit stable species-specific differences in time and space. Here, we describe phenotypic patterns of inter- and intraspecific variation in the male perfumes of three sympatric species of Euglossa orchid bees across an entire year, investigating both their seasonality and species specificity. Our analysis revealed considerable within-species variation in perfumes. However, species specificity was maintained consistently throughout the year, supporting the idea that these perfumes could play an important role in reproductive isolation and are experiencing stabilizing selection towards a species mean. Our analysis also identified strong correlations in the abundance of some compounds, possibly due to shared collection sources between species. Our study suggests that orchid bee perfumes are robust in the face of environmental changes in resource availability and thus can maintain reproductive isolation between species.

Mate choice is posited to explain the evolution and maintenance of numerous secondary sexual traits, including ornamentation. This study explores the role of ornamentation in the mating success of two sister-species of wolf spider with divergent ornamentation. Mature male Schizocosa crassipalpata lack ornamentation while males of its closest living relative, S. bilineata, express both dark pigmentation and foreleg brushes. Following phenotypic manipulations of foreleg ornamentation – i.e. adding ornamentation in the form of dark pigment to non-ornamented males (S. crassipalpata, Aim 1) and removing ornamentation in varying degrees from highly ornamented males (S. bilineata, Aim 2 – shaving brushes; Aim 3 – shaving brushes and painting over dark pigment in vibration present/absent environments) – we found no evidence that ornamentation alone improves male mating success in either species, regardless of the vibratory signaling environment. In both S. bilineata experiments, however, higher courtship rates resulted in higher mating success, suggesting selection for courtship performance. Furthermore, females were more likely to turn, a presumed receptivity display, in response to males that courted at a higher rate. Also, similar to findings in another relative (S. stridulans), we found indications that ornamentation may function to ease a male’s reliance on courtship performance – i.e., at low courtship rates, only ornamented males can secure a mating. Our phenotypic manipulations also influenced courtship behavior in S. bilineata. Shaved males began courting earlier and courted more often over a longer time than intact males, yet ultimately acquired similar matings. This increased courtship effort likely compensated for reduced ornamentation. Finally, the vibratory environment appears crucial for female–male dialogue in S. bilineata, as vibratory absent environments resulted in increased female attacks and decreased male courtship rates. Together, our data suggest that S. crassipalpata females do not possess a preference for ornamentation and that S. bilineata females do not use ornamentation alone in mating decisions. Instead, our results are consistent with a hypothesis that ornamentation in Schizocosa evolved, and is likely maintained, due to its interactions with dynamic movement displays (i.e. leg movements), which can themselves be plastically altered based on the signaler’s phenotype as well as the signaling environment.

Abstract Multiple cues are often used for mate choice in complex environments, potentially entailing mismatches in the information conveyed by different sources. We address the consequences of this information mismatch for receivers using the spider mite Tetranychus urticae, in which virgin females are highly valuable mates compared to mated females, given first male sperm precedence. Accordingly, males are known to prefer virgins and distinguish them using cues from the females themselves and that they leave on the substrate. Whereas cues from females are highly reliable, those left on the substrate may not reflect the real female mating status if females move and/or mate. Here, we tested the consequences of such mismatch by exposing males to mated or virgin females on patches previously impregnated with cues deposited by females of either mating status. Male mating attempts were solely affected by substrate cues while female acceptance and the number of mating events were independently affected by both cues. Copulation duration, in contrast, depended mainly on the mating status of the female, with the number of copulations and the total time spent mating being intermediate in environments with mismatched information. We also show that males incur mating costs, reflected in reduced survival in environments with virgin cues. These results suggest that substrate cues left by females are instrumental for males to find their mates. However, in environments with mismatched information, males may pay survival costs without the associated benefit of mating with virgins, or they may lose opportunities to mate with virgins by responding to substrate cues from mated females. The benefit of using multiple cues will then hinge upon the frequency of information mismatch, which itself should vary with the dynamics of populations.

Background Darwin assumed that the peacock’s long train was maladaptive and was the indirect effect of selection by female mate choice based on the train’s beauty. While a relationship between the feathers’ elaborate features and mating success has been shown, what features of the train females are attracted to remains controversial. Methods We used museum specimens to examine the anatomical plan underlying feather development responsible for the symmetry of the train. We developed a model based on an alternate arrangement of primordial feather buds during development and locations of concentric circles of symmetric eyespot distribution using the pattern seen on the train as a template. Results We observed a zigzag pattern of feather follicles that determined both the number and the hexagonal arrangement of eyespots on the train. Our model explained not only the alternate arrangement of feathers on the train but also the arrangement of the concentric color rings of the eyespots. While the zigzag pattern explains the symmetry, complexity, and structural beauty of the peacock’s train, it also precludes variation in eyespot number except by annual addition of new rows of feathers as a function of age. Conclusions Since eyespot number and feather length are developmentally correlated and an asymptotic function of a male’s age, their effects on female choice would be confounded and inseparable, and male vigor would be a crucial factor affecting male fitness. Females may not always choose males with the largest number of eyespots, as older males may lack vigor. We propose a multimodal model of female choice where females see eyespot and train size not as separate traits but as one complex trait combining both. The new model may be able to explain conflicting results and why eyespot number alone may not be sufficient to explain female choice.

Maintenance of variation in aposematic traits within and among populations is paradoxical because aposematic species are normally under positive frequency-dependent predation (PFD), which is expected to erode variation. Aposematic traits can evolve in an ecological context where aposematic traits are simultaneously under mate choice. Here, we examine how the mate preference intensity affects the permissiveness of polymorphism in sexually selected aposematic traits under different PFD regimes. We use the haploid version of the classical sexual selection model and show that strong mate preferences can substantially increase the permissiveness of polymorphism in aposematic traits under different PFD regimes. The Fisher process can interact with PFD, and their interaction can promote the maintenance of polymorphism within populations when mate preferences are strong. We show that the same selective conditions that promote the maintenance of polymorphism within populations reduce the likelihood of divergence in aposematic traits among populations.

Where orangethroat darters (Etheostoma: Ceasia) and rainbow darters (Etheostoma caeruleum) co‐occur, males prefer conspecific over heterospecific females. The cues males use to identify conspecific females remain unclear. We conducted behavioral trials to ask whether chemical cues function in conspecific recognition. We found that males from three orangethroat darter species preferentially associate with female scent over a control. Our results support the use of olfaction in conspecific identification in the orangethroat clade and contribute to our understanding of signals that may facilitate species recognition and underlie the evolution of behavioral isolation. [ABSTRACT FROM AUTHOR]

Traits under divergent ecological selection that also function during mating can be important in maintaining species boundaries. Few studies have considered mutual mate choice, where both males and females base mating decisions on the same trait. Wing colouration in Heliconius butterflies evolved as a warning signal but also functions as a mating cue. We investigated the contribution of visual preference to assortative mating in an aposematic butterfly Heliconius cydno in the context of reproductive isolation with its sympatric, visually distinct relative Heliconius melpomene. Heliconius cydno have conspicuous white bands on their forewings, whereas those of H. melpomene are red in colour. We predicted that both sexes of H. cydno contributed to assortative mating by exhibiting visual preference towards conspecific wing colouration. We analysed published and new data from preference experiments, in which males were presented with conspecific and H. melpomene females. We also recorded female responses and mating outcomes in choice experiments, involving conspecific males with either the original white or artificially painted red forewing bands. Both sexes of H. cydno responded more positively towards the conspecific colouration, and males strongly preferred females of its own colours. In contrast, male colouration did not predict mating outcomes in female choice experiments. As courtships are initiated by males in butterflies, our findings suggest that female visual preference might be of secondary importance in H. cydno. Our data also suggest that the contribution of visual preference to reproductive isolation might be unequal between H. cydno and its sympatric relative H. melpomene. [ABSTRACT FROM AUTHOR]

Sexual traits may be selected during multiple consecutive episodes of selection, occurring before, during, or after copulation. The overall strength and form of selection acting on traits may thus be determined by how selection (co-)varies along different episodes. However, it is challenging to measure pre- and postcopulatory phenotypic traits alongside variation in fitness components at each different episode. Here, we used a transgenic line of the transparent flatworm Macrostomum lignano expressing green fluorescent protein (GFP) in all cell types, including sperm cells, enabling in vivo sperm tracking. We assessed the mating success, sperm-transfer efficiency, and sperm fertilizing efficiency of GFP(+) focal worms in which we measured 13 morphological traits. We found linear selection on sperm production rate arising from pre- and postcopulatory components and on copulatory organ shape arising from sperm fertilizing efficiency. We further found nonlinear (mostly concave) selection on combinations of copulatory organ and sperm morphology traits arising mostly from sperm-transfer efficiency and sperm fertilizing efficiency. Our study provides a fine-scale quantification of sexual selection, showing that both the form and strength of selection can change across fitness components. Quantifying how sexual selection builds up along episodes of selection allows us to better understand the evolution of sexually selected traits. [ABSTRACT FROM AUTHOR]

The preference of females for male body size was examined in an experimental environment where direct interference between males was eliminated. In this environment, females preferred to spawn with larger males. To understand the preference of females for larger males, paternal care and egg defence abilities and paternal cannibalism intensity were further tested with respect to the body size of males. The dead egg rate for an egg mass during the paternal care period was not related to the body size of the paternal males. However, larger males could defend their egg masses more successfully against nest intruders than smaller ones. During the paternal egg care period, paternal males often consumed eggs in their nests. In particular, smaller males compared to females caused paternal brood cannibalism. High egg defence ability and low paternal cannibalism intensity are the most plausible reasons for females to choose larger males. [ABSTRACT FROM AUTHOR]

Animal-built structures that function in mate attraction can be constrained in signal expression by the availability of building materials in the environment and the male's ability to find them as well as the ability to construct the structure itself. As part of their courtship display, male great bowerbirds, Ptilonorhynchus nuchalis , use hundreds of grey-white objects to create a bower court. Males arrange these objects to create a positive size–distance gradient, the evenness of which generates a forced perspective visual illusion that is associated with mating success. However, a range of differently sized objects are required to build a high-quality gradient, and it is unclear how local object availability and male ability to place objects in the correct location (i.e. building ability) affect gradient quality. To disentangle these effects, we provided males with a standardized set of court objects after removing their original objects. If gradient quality is associated with male building ability, we predicted that the quality of the gradient constructed with the standardized set of objects would be positively correlated with the male's original gradient quality. Contrary to our predictions, males that built high-quality gradients in their original court did not build high-quality gradients when given a standardized set of objects. We conclude that the bower court may not be a reliable signal of male building ability, and that object availability and/or male ability to locate appropriate objects explains some of the observed variation in gradient quality. • Male great bowerbirds readily rebuild bower courts with supplied objects. • Natural difference in court quality is not maintained with standardized objects. • Local object availability not male building ability likely affects court quality. [ABSTRACT FROM AUTHOR]

In this theoretical review, we examine how the roles of music in mate choice and social bonding are expressed in romantic relationships. Darwin's Descent of Man originally proposed the idea that musicality might have evolved as a sexually selected trait. This proposition, coupled with the portrayal of popular musicians as sex symbols and the prevalence of love-themed lyrics in music, suggests a possible link between music and attraction. However, recent scientific exploration of the evolutionary functions of music has predominantly focused on theories of social bonding and group signaling, with limited research addressing the sexual selection hypothesis. We identify two distinct types of music-making for these different functions: music for attraction, which would be virtuosic in nature to display physical and cognitive fitness to potential mates; and music for connection, which would facilitate synchrony between partners and likely engage the same reward mechanisms seen in the general synchronybonding effect, enhancing perceived interpersonal intimacy as a facet of love. Linking these two musical functions to social psychological theories of relationship development and the components of love, we present a model that outlines the potential roles of music in romantic relationships, from initial attraction to ongoing relationship maintenance. In addition to synthesizing the existing literature, our model serves as a roadmap for empirical research aimed at rigorously investigating the possible functions of music for romantic relationships. [ABSTRACT FROM AUTHOR]

Mate choice is hypothesized to play an important role in maintaining high diversity at major histocompatibility complex (MHC) genes in vertebrates. Many studies have revealed that females across taxa prefer the scent of males with MHC genotypes different to their own. In this study we tested the "opposites‐attract" hypothesis in two species of darter with known differences in female criteria used in mate choice: in the fantail darters (a paternal‐care species), females prefer males with visual traits related to nest guarding and egg tending, while in rainbow darters (not a paternal‐care species) female mate choice criteria are unknown. In dichotomous mate‐choice trials, we presented females of both species with the scents of conspecific males with MHC class IIb genotypes that were either similar or dissimilar to that of the focal female. We evaluated the proportion of time each female spent with each male and calculated the average strength of female preference for both species. Female fantail darters demonstrated a preference for the scent of males with similar (rather than dissimilar) MHC genotypes, but this result was not statistically significant. Rainbow darter females showed no preference for the scent of males with similar or dissimilar MHC genotypes. Our results do not support the "opposites‐attract" hypothesis in darters. [ABSTRACT FROM AUTHOR]

Sex pheromones are species-specific chemical signals that facilitate the location, identification, and selection of mating partners. These pheromones can vary between individuals, and act as signals of mate quality. Here, we investigate the variation of male pheromones in the mesosomal glands of the large carpenter bee Xylocopa sonorina, within a Northern California population. We tested the hypothesis that morphological traits are correlated with the observed variation in chemical blend composition of these bees. We also conducted behavioral assays to test whether these male pheromones act as long-range attractants to conspecifics. We found that larger males with darker mesosomal glands have a higher pheromone amount in their glands. Our analysis also suggests that this pheromone blend functions as a long-range attractant to both males and females. We show that both male body size and sexual maturation are important factors influencing pheromone abundance, and that this pheromone blend acts as a long-range attractant. We hypothesize that this recorded variation in male pheromone could be important for female choice. [ABSTRACT FROM AUTHOR]

In the terminal investment strategy, organisms allocate resources to maximize current reproduction when their future reproductive opportunities are uncertain due to a high risk of mortality. However, whether the role of time lapse between stress and reproductive investment (courtship vs. courtship and mating) triggers the terminal investment strategy remains unknown.We examined this hypothesis in Tenebrio molitor using oxidative stress as the stressor. Given that this is the first time that oxidative stress is used to trigger terminal investment, we first conducted mate choice trials where males exposed to 5, 20, 40 or 80 mM of the pro‐oxidant, paraquat (PQ) engaged in courtship behaviour towards the females. Subsequently, we analysed the male mortality against each of these doses.Males exposed to a 5 mM treatment exhibited higher survival rates compared with the control group, whereas males exposed to 80 mM experienced a shorter lifespan. After courtship, no significant differences in mortality were observed between the control group and those treated with 20 or 40 mM of PQ. Notably, only males exposed to 40 mM of PQ were preferred over the control group.In a third experiment, we quantify the survival costs when males courted and mated at varying time intervals after oxidative stress (40 mM). When males were exposed to 40 mM of PQ and mated 3 h later, their mortality rates significantly decreased compared with males exposed to oxidative stress, courted and mated, but 24 h later.We suggest that the interaction of the dose of oxidative stress and the time lapse between courtship and mating may explain opposed results to support either the terminal investment or honest signalling. [ABSTRACT FROM AUTHOR]

Female mate choice is usually based on traits that signal male quality as a sexual partner. According to the "good parent" hypothesis, female mate choice may also consider male quality as a caregiver in species with male-only care. Because parental activities may be costly, males in good condition should be more attractive to females than those in poor condition. We experimentally manipulated the body condition of non-parental and parental males of the egg-tending harvestman Iporangaia pustulosa and then evaluated how it affected their mating success and ability to protect eggs under field conditions. For non-parental males, individuals in good condition had twice the probability of mating than those in poor condition. For parental males, individuals in good condition had two times more chances of mating and acquired five times more eggs than those in poor condition. Surprisingly, males' body condition had no effect on the efficiency of egg protection. Although our results indicate that the male condition is a sexually selected trait, we found no support for the "good parent hypothesis" given that an increase in body condition does not improve the survival of the offspring under male care. Instead, these findings are congruent with predictions of the "essential male care" model, which suggests that, when the costs of parental care are low (as is the case of egg attendance), most males can provide the minimum necessary care for offspring survival. However, only males in good condition can allocate surplus energy to advertise their overall quality and attract more mates. Significance statement: Studies examining female mate choice based on condition-dependent traits that serve as reliable indicators of male caregiving quality are mostly limited to vertebrates. We present one of the first empirical examples demonstrating that male body condition influences male attractiveness in an arthropod species exhibiting male-only care. Our field-based results show that females prefer males, whether non-parental or parental, in good body condition over those in poor condition. However, we found no evidence that an increase in body condition improves the survival of the offspring under male care. We propose that males in good body condition are more attractive because the relatively low costs of egg attendance allow them to allocate their surplus energy into advertising their overall quality. Our findings are congruent with predictions of the "essential male care" model, which explores resource allocation between paternal care and sexual advertising. [ABSTRACT FROM AUTHOR]