Sexual Selection - Science topic

Bird song has historically been characterized as a primarily male behavior that evolves through sexual selection pressures involved in mate attraction. More recently, researchers showed that female song is far more prevalent in songbirds than previously thought, raising new questions about how other social functions of birdsong and sexual selection...

Sex differences in early‐life survival can drive skewed adult sex ratios (ASR), which play an important role in mating tactics and parental sex roles. Among birds, cuckoos exhibit the largest diversity in mating systems and thus represent an interesting system to study sex‐specific demography. Here we investigate the early‐life survival pathways sh...

In internal fertilisers, the precise timing of ovulation with the arrival of sperm at the site of fertilisation is essential for fertilisation success. In birds, mating is often not synchronised with ovulation, but instead females utilise specialised sperm storage tubules (SSTs) in the reproductive tract, which can ensure sperm are always available...

Copulatory organs are a key trait in reproductive compatibility and sexual isolation. The role of male genitalia in boosting mating success is well known and is often the outcome of behavioural and biological constraints, although no clear and common interpretation about their evolution appears broadly applicable. In snakes, hemipenial morphology h...

Cryptic female choice (CFC) is a component of postcopulatory sexual selection that allows females to influence the fertilization success of sperm from different males. While its precise mechanisms remain unclear, they may involve the influence of the protein composition of the female reproductive fluids on sperm functionality. This study maps the p...

Non-iridescent structural plumage reflectance is a sexually selected indicator of individual quality in several bird species. However, the structural basis of individual differences remains unclear. In particular, the dominant periodicity of the quasi-ordered feather barb nanostructure is of key importance in colour generation, but no study has suc...

Ultraviolet (UV) colour patterns invisible to humans are widespread in nature. However, research bias favouring species with conspicuous colours under sexual selection can limit our assessment of other ecological drivers of UV colour, like interactions between predators and prey. Here we demonstrate widespread UV colouration across Western Hemisphe...

Heavy metal pollution is known to negatively affect numerous traits in birds, including foraging, metabolism, immunity, and reproductive success. In this study, our primary aim was to assess the impact of metal pollution exposure on the visual appearance of the pied flycatcher Ficedula hypoleuca eggs. Specifically, we focused on blue‐green biliverd...

Many species often show male–male combat for mating opportunities and resources within the species. Sexual selection through this radical combat leads to the evolution of males with exaggerated traits used as weapons, such as horns or mandibles, that often result in victory during combat. However, heterospecific interaction due to errors in species...

Sexual dimorphisms are generated by divergent processes, such as natural or sexual selection and niche convergence. Males and females of the lesser guitarfish, Zapteryx brevirostris, present morphological differences in their discs, and the relationships with the species biology and ecology were unrecognized. Analysing the morphometry of 201 specim...

Linking reproductive fitness with adaptive traits at the genomic level can shed light on the mechanisms that produce and maintain sex‐specific selection. Here, we construct a multigenerational pedigree to investigate sex‐specific selection on a maturation gene, vgll3 , in a wild Atlantic salmon population. The vgll3 locus is responsible for ~40% of...

For over a century, the role of acoustic communication in the sensory ecology of bark beetles (Scolytinae) has been recognized. However, their 'world of sound' remains largely unexplored. Here, we review 153 years of bark beetle bioacoustics publications to summarize current knowledge, identify gaps and suggest future research directions. Our surve...

This article delves into the multifaceted mechanisms driving evolution, exploring the foundational principles of natural selection alongside advanced theories of cybernetics, symbiogenesis, and autopoiesis. Charles Darwin's concept of natural selection highlights the gradual adaptation of organisms, favoring traits that enhance survival and reprodu...

Males display phenotypic characteristics that may be associated with their quality, allowing non-random mating and post-copulatory female choice. In the damselfly Calopteryx haemorrhoidalis asturica, males have a conspicuous pink colouration in the underside of abdominal segments 8–10, which they exhibit during pre- and post-copulatory courtship. W...

In birds, males are homogametic and carry two copies of the Z chromosome (‘ZZ’), while females are heterogametic and exhibit a ‘ZW’ genotype. The Z chromosome evolves at a faster rate than similarly sized autosomes, a phenomenon termed ‘fast-Z evolution’. This is thought to be caused by two independent processes—greater Z chromosome genetic drift o...

Immunocompetence evolution can involve a "resistance is futile" scenario, if parasite encounter rates are so high that high investment in resistance only marginally delays infection. Here, we investigate two understudied aspects of "futility". First, immunocompetence is usefully categorized as reducing the rate of becoming infected (resistance) or...

We investigated post-settlement growth patterns and sexual dimorphism in the carapace, pelon, and cheliped dimensions of the varunid crab Gaetice depressus (De Haan, 1833). We reared crabs in the laboratory from hatching through megalopae to the first to tenth instars, and measurements were made of exuviae or specimens of crabs that successively mo...

Male-biased adult sexual size dimorphism is often the result of intra-sex sexual selection driven by male-male competition. Capelin (Mallotus villosus) exhibit male-biased sexual size dimorphism but lack contests/fighting, and female mate choice, if present, is unrelated to male size. Consequently, it is hypothesized that adult sexual size dimorphi...

Biologists have long wondered how sexual ornamentation influences a species' risk of extinction. Because the evolution of condition‐dependent ornamentation can reduce intersexual conflict and accelerate the fixation of advantageous alleles, some theory predicts that ornamented taxa can be buffered against extinction in novel and/or stressful enviro...

Both sexually selected traits and mate preferences for these traits can be context dependent, yet how variation in preferred traits could select for context dependent preferences has rarely been examined. The signal reliability hypothesis predicts that mate preferences vary across contexts (e.g., environments) in relation to the reliability of the...

The karyotype of an organism is the set of gross features that characterize the way the genome is packaged into separate chromosomes. It has been known for decades that different taxonomic groups often have distinct karyotypic features, but whether selective forces act to maintain these differences over evolutionary timescales is an open question....

Passerines are the most successfully diversified bird order (around 60% of all avian species). They have developed complicated songs to defend their territories and to attract females for mating that can evolve quickly due to cultural transmission. Complex singing as well as plumage coloration of male birds are honest signals for potential partners...

Sexual selection theory predicts that males, especially in their prime reproductive years, are more risk-prone than females. Risk-taking is a means to convey mate quality or “good genes” to members of the opposite sex or competitive ability to members of the same sex. Therefore, risk-taking should be more common in the presence of potential mates (...

When it comes to describe reproduction in internally fertilized species, understanding the dynamics of sperm storage is crucial to unravel the complexity of post-copulatory sexual selection processes. This physiological process goes from sperm transfer to its use for fertilization. In this framework, the spatiotemporal dynamics of sperm storage wer...

Giraffes exhibit a large sexual dimorphism in body size. Whether sexual dimorphisms also exist in body proportions of the axial and appendicular skeleton has been debated, particularly regarding the giraffe’s iconic long neck. We examined the anatomical proportions of the neck, forelegs, hindlegs, and body trunk of the Masai giraffe ( G. tippelskir...

The present review provides a compilation of the published data on the phenomena of multiple mating by females and multiple paternity in their litters in 48 rodent species with different mating systems, reproductive strategies, and social structures. Multi-male mating is common in female rodents, but this is one of the unsolved problems of behavior...

Placerias hesternus, a Late Triassic dicynodont, is one of the last megafaunal synapsids of the Mesozoic. The species has a tusk-like projection on its maxillary bone, known as the caniniform process. This process has been hypothesized to be sexually dimorphic since the 1950s, however this claim has not been thoroughly investigated quantitatively....

Tourism pressure on the Red Sea ecosystem have posed significant threats to numerous endemic species, including the Ghost Crab Ocypode saratan, which is exclusively found along a small stretch of beach in the Eilat/Aqaba Red Sea Gulf. Due to the limited understanding of their ecology, we investigated how tourism impacts the behavior of this species...

While rhythm can facilitate and enhance many aspects of behavior, its evolutionary trajectory in vocal communication systems remains enigmatic. We can trace evolutionary processes by investigating rhythmic abilities in different species, but research to date has largely focused on songbirds and primates. We present evidence that cetaceans—whales, d...

Animal culture evolves alongside genomes, and the two modes of inheritance—culture and genes—interact in myriad ways. For example, stable geographic variation in culture can act as a reproductive barrier, thereby facilitating genetic divergence between “cultural populations.” White-crowned sparrows (Zonotrichia leucophrys) are a well-established mo...

Artificial intelligence (AI) technologies are increasingly used in conservation practices, e.g., to prevent poaching or inventory wildlife. Another area of application is using AI to decode animal vocalisations to understand better-and subsequently better protect-the animals. It has already been applied to different species, including various whale...

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...

Most species co-evolve with their predators and develop strategies to avoid predation. This is not possible when a novel predator invades an environment. Native residents must quickly adapt to their new predator or face local extinction. Intense competition for mating opportunities exerts significant selective pressure that can drive the evolution...

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 romanti...

When males compete, sexual selection favors reproductive traits that increase their mating or fertilization success (pre- and postcopulatory sexual selection). It is assumed that males face a trade-off between these 2 types of sexual traits because they both draw from the same pool of resources. Consequently, allocation into mate acquisition or eja...

The large nose adorned by adult male proboscis monkeys is hypothesised to serve as an audiovisual signal of sexual selection. It serves as a visual signal of male quality and social status, and as an acoustic signal, through the expression of loud, low-formant nasalised calls in dense rainforests, where visibility is poor. However, it is unclear ho...

In some squids, such as those in the family Loliginidae, upon copulation, females receive and store male-delivered sperm capsules, spermatangia, at two different body locations: the buccal membrane and the distal end of the oviduct. This insemination site dimorphism is associated with alternative reproductive strategies. However, in Loliolus sumatr...

Another person’s caring abilities, in addition to physical features, may affect the observed attractiveness of that person. Using two newly developed instruments, we tested whether women (N = 360) judge men as more attractive when they are depicted in interactions with children (picture task) or accompanied by information on caring behavior (vignet...

Speciation is often driven by selective processes like those associated with viability, mate choice, or local adaptation, and “speciation genes” have been identified in many eukaryotic lineages. In contrast, neutral processes are rarely considered as the primary drivers of speciation, especially over short evolutionary timeframes. Here, we describe...

The existence of adult sexual dimorphism is typically explained as a consequence of sexual selection, yet coevolutionary drivers of sexual dimorphism frequently remain untested. Here, I investigate the role of sexual dimorphism in host–parasite interactions of the brood parasitic diederik cuckoo, Chrysococcyx caprius. Female diederik cuckoos are mo...

Synopsis The cost of supporting traits that increase mating opportunities and maximize the production of quality offspring is paid in energy. This currency of reproduction is enabled by bioenergetic adaptations that underlie the flexible changes in energy utilization that occur with reproduction. This review considers the traits that contribute to...

Hybrid zones are dynamic systems where natural selection, sexual selection, and other evolutionary forces can act on reshuffled combinations of distinct genomes. The movement of hybrid zones, individual traits, or both are of particular interest for understanding the interplay between selective processes. In a hybrid zone involving two lek-breeding...

Lucihormetica verrucosa (Blattodea, Blaberidae) are highly sexually dimorphic cockroaches, with the males having two symmetrically organised ‘glowspots’ on their pronotum. The spots can range in colour from whitish-yellow to red, depending on the quantity of carotenoids in their diet. These spots auto-fluoresce when exposed to UV wavelengths, with...

Sexual selection predicts that males invest in sperm competition when females mate with multiple males. Because group residency facilitates access to mates, we hypothesized that variation in within-group mate competition influences investment in sperm competition. Verreaux’s sifaka (Propithecus verreauxi) live in both single and multimale groups, a...

Changing patterns of warfare require a revision of our theories of psychological mechanisms behind violent conflict. The article explains some evolutionary theories that can improve our understanding of the deep-rooted psychological mechanisms behind bellicosity, radicalization, escalation, and cultural changes related to war. An evolutionary theor...

Sperm competition is a potent mechanism of post-copulatory sexual selection that has been found to shape reproductive morphologies and behaviours in promiscuous animals. Especially sperm size has been argued to evolve in response to sperm competition through its effect on sperm longevity, sperm motility, the ability to displace competing sperm and...

Predicting the strength and direction of sexual selection is a challenging task for evolutionary theory, as the effects of ecological factors, social environment, and behavioural plasticity, all need to be taken into account. The Operational Sex Ratio (OSR) is a key variable, which has been shown to (i) affect the strength and direction of mating c...

How did our distant ancestors defend themselves from lethal African predators after they moved from the trees to the ground and started sleeping in the open? Strangely, this important question of human evolutionary history has been largely ignored by scholars. For Charles Darwin, humans did not need to defend themselves from predators, as they evol...

Sexual selection often drives traits in a direction that is disfavored by natural selection. The balance between these two types of selection can shift rapidly in response to environmental changes. Gallagher et al. (2024) report such a shift in a cricket population following the introduction of a parasitoid fly. The ancestral male morph, though sti...

Gamete traits can vary widely among species, populations and individuals, influencing fertilisation dynamics and overall reproductive fitness. Sexual selection can play an important role in determining the evolution of gamete traits with local environmental conditions determining the strength and direction of sexual selection. Here, we test for sig...

Ecological differences between human populations can affect the relative strength of sexual selection, and hence drive gender inequality. Here, we exploit the cultural diversity of southwestern China, where some village sex ratios are female-biased, in part due to a proportion of males entering monastic celibacy, to evaluate the role of sex ratio o...

The objectives of this article are to prove that Darwin's theory of Sexual selection is opposite to the Descent of Man (Human evolution) from the lower animal like a chimpanzee. According to Darwin, humans evolved from a lower animal through sexual selection. However, literature claims that sexual selection is absent in all kinds of animals; as sex...

Seminal fluid protein composition is complex and commonly assumed to be rapidly divergent due to functional interactions with both sperm and the female reproductive tract (FRT), both of which evolve rapidly. In addition to sperm, seminal fluid may contain structures, such as mating plugs and spermatophores. Here, we investigate the evolutionary div...

The intensity and direction of sexual selection is intricately linked to the social and ecological context. Both operational sex ratios (OSRs) and population densities can affect the ability of males to monopolize resources and mates, and thus the form and intensity of sexual selection on them. Here, we studied how the mating system of the promiscu...

Females that mate multiply make postmating choices about which sperm fertilize their eggs (cryptic female choice); however, the male characteristics they use to make such choices remain unclear. In this study, we sought to understand female sperm use patterns by evaluating whether Drosophila melanogaster females adjust sperm use (second male patern...

Sexual selection can result in the evolution of extreme armaments and ornaments, and the development and maintenance of these traits can come at a considerable cost. These costs have been implicated in enforcing an upper limit on trait divergence and promoting condition-dependent traits, such that only individuals in sufficiently high condition can...

Animal colouration may evolve due to its effects on predator avoidance, reproduction and thermoregulation, and is likely influenced by the organism’s diel activity. The dung beetle species of the Phanaeini tribe (Coleoptera: Scarabaeinae) show a wide variety of times of activity and pre-copulatory behaviours. Here we tested the effect of time of ac...

In anurans, acoustic communication is the most important form of communication at the interspecific and intraspecific levels. Acoustic diagnostic features may be a potential alternative to morphometric and molecular diagnostics. Here, we assessed the variations in advertisement calls between two sympatric species, Boulenophrys leishanensis and Boul...

Vocal rhythm plays a fundamental role in sexual selection and species recognition in birds, but little is known of its genetic basis due to the confounding effect of vocal learning in model systems. Uncovering its genetic basis could facilitate identifying genes potentially important in speciation. Here we investigate the genomic underpinnings of r...

Sperm ultrastructure is frequently employed as a source for phylogenetic inference due to the ease of accessing spermatozoa. Despite being unicellular, sperm cells exhibit a relatively high number of diverse characters and character states. Spermatozoa are subject to strong sexual selection as they are finely tuned for maximizing male reproductive...

Contingency (or 'luck') in early life plays an important role in shaping individuals' development. When individuals live within larger societies, social experiences may cause the importance of early contingencies to be magnified or dampened. Here we test the hypothesis that competition magnifies the importance of early contingency in a sex-specific...

The great diversity of specialist plant-feeding insects suggests that host plant shifts may initiate speciation, even without geographic barriers. Pheromones and kairomones mediate sexual communication and host choice, and the response to these behaviour-modifying chemicals is under sexual and natural selection, respectively. The idea that the inte...

Vertebrates host complex microbiomes that impact their physiology. In many taxa, including colourful wood-warblers, gut microbiome similarity decreases with evolutionary distance. This may suggest that as host populations diverge, so do their microbiomes, because of either tight coevolutionary dynamics, or differential environmental influences, or...

The rate and chromosomal positioning of meiotic recombination significantly affects the distribution of the genetic diversity in eukaryotic genomes. Many studies have revealed sex-specific recombination patterns, with male recombination typically biased toward chromosome ends, while female recombination is more evenly distributed along chromosomes,...

Coloration in wildlife serves numerous biological purposes, including sexual selection signaling, thermoregulation, and camouflage. However, the physical appearance of wildlife also influences the ways in which humans interact with them. Wildlife conservation has largely revolved around humans’ propensity to favor charismatic megafauna, but human p...

Simple Summary Phenotypic difference between males and females (sexual dimorphism) is widespread in animals. These sexual dimorphisms, in particular vocalizations and acoustic signals, have been shown to play important roles in mating choice and sexual selection. However, little is known about the molecular mechanisms underlying these phenotypic va...

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 o...

Pronounced sexual dimorphism is thought to evolve through sexual selection for elaborate male traits. Increasing evidence suggests that sexual dimorphism in traits such as birdsong may also evolve through loss of elaboration in females, but the evolutionary drivers underlying this are obscure. Here we analyse ecological and natural history traits o...

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,...

Bite force is an important performance indicator of individual fitness that is closely related to food acquisition, male competition, and mating selection. It is also affected by a variety of factors and different mechanisms. Therefore, it is relatively difficult to understand the evolutionary driving forces of changes in bite force. In this study,...

While mortality is often the primary focus of pathogen virulence, non‐lethal consequences, particularly for male reproductive fitness, are less understood; however, they are essential for understanding how sexual selection contributes to promoting resistance. We investigated how the fungal pathogen Metarhizium brunneum affects mating ability, ferti...

This inquiry seeks to counter a hypothesis advanced by Jon D. Wisman, stating that Thorstein Veblen "missed" the opportunity to incorporate sexual selection into his evolutionary economics. To the contrary, I argue that Veblen's vision is far from lacking, and that he intentionally refrained from integrating the biological process of sexual selecti...

The maintenance of polymorphisms often depends on multiple selective forces, but less is known on the role of stochastic or historical processes in maintaining variation. The common wall lizard (Podarcis muralis) is a colour polymorphic species in which local colour morph frequencies are thought to be modulated by natural and sexual selection. Here...

In species where females compete for mates, the male often provides the female with resources in addition to gametes. A recently suggested definition of sexual selection proposed that if females only benefit from additional resources that come with each mating and not additional gametes, female intrasexual competition for mating opportunities would...

Colours are well studied in bird plumage, but not in other integumentary structures. In particular, iridescent colours from structures other than plumage are undescribed in birds. Here, we show that a multilayer of keratin and lipids is sufficient to produce the iridescent bill of Spermophaga haematina. Furthermore, that the male bill is presented...

Body size is undoubtedly one of the most useful measures of sexual dimorphism and, by proxy, sexual selection. Here, I examine large, published datasets of average sexual size dimorphism (SSD) in four clades of amniotes: birds, mammals, squamates, and turtles. Most sexual variation is of subtle magnitude; attempts to discretely categorize species a...

Intraspecific sexual dimorphism between males and females is tied to sexual selection, such as body features and color patterns. Sexual selection pressure in the genus Giuris may occur in either or both sexes. The present study aimed to analyze the sexual dimorphism of Hulu’u fish (Giuris sp. Limboto) from Limboto Lake, Gorontalo Province, North...

Sperm competition and cryptic female choice (CFC) are 2 significant mechanisms of postcopulatory sexual selection that greatly impact fertilization success in various species. Despite extensive research has conducted on sperm competition and the evolution of sperm traits in internal fertilization, our understanding of the female preferences in sele...

The bright colors of Alpine leaf beetles (Coleoptera, Chrysomelidae) are thought to act as aposematic signals against predation. Within the European Alps, at least six species display a basal color of either blue or green, likely configuring a classic case of müllerian mimicry. In this context, intra-population color polymorphism is paradoxical as...

Reproducibility is a fundamental principle in science, ensuring reliable and valid findings. However, replication studies are scarce, particularly in ecology, due to the emphasis on novelty for publication. We explored the possibility of replicating original findings in the field of microbial and chemical ecology by conducting a conceptual replicat...

When males have large sperm, they may become sperm limited and mating dynamics may be affected. One such species is Zaprionus indianus , a drosophilid that is an introduced pest species in the Americas. We examined aspects of mating behavior in Z . indianus to determine the senses necessary for mating and measure female and male remating habits. We...

Background We used college-level evolution textbooks to examine the presentation of sexual selection research—a field with ongoing debates related to sex, sexuality and gender identity. Many classic sexual selection concepts have been criticized for androcentrism and other forms of gender-sex bias, specifically for de-emphasizing the female role in...

Otherwise, apparently cryptic mammals often have conspicuous patches of colour on distal regions of their body, possibly for signalling. To investigate ideas about communication within sociosexual contexts, we used a comparative dataset for 2726 terrestrial mammals to match the coloration and patterning of distal body areas (head, chest, rump and t...

Inter-sexual mate competition occurs any time opposite-sex individuals simultaneously seek to acquire or maintain exclusive access to the same sexual partner. This underappreciated form of mate competition has been anecdotally documented in several avian and mammalian species, and systematically described among Japanese macaques and humans. Here, w...

Scapular morphology is highly variable across the human population and appears to be sexually dimorphic - differing significantly between males and females. However, previous investigations of sexual dimorphism in scapula shape have not considered the effects of allometry (the relationship between size and shape). Disentangling allometry from sexua...

Vocal learning in songbirds is thought to have evolved through sexual selection, with female preference driving males to develop large and varied song repertoires1–3. However, many songbird species learn only a single song in their lifetime⁴. How sexual selection drives the evolution of single-song repertoires is not known. Here, by applying dimens...

Speciation can be mediated by a variety of reproductive barriers, and the interaction among different barriers has often been shown to enhance overall reproductive isolation, a process referred to as 'coupling'. Here, we analyze a population genetics model to study the establishment of linkage disequilibrium (LD) among loci involved in multiple pre...