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Despite the great diversity of parental care types found in amphibians, studies linking them to post-copulatory sexually selected traits are scarce, presumably due to a lack of data. Valencia-Aguilar et al. used fieldwork and museum collections to show that paternal care appears to trade-off with testes size in glass frogs. [ABSTRACT FROM AUTHOR]

Male genitalia have been hypothesized to function as courtship devices during copulation, but it is difficult to use behavioral observations to test this hypothesis because male genitalia are usually hidden inside the female during copulation. In tipuloid flies, however, nearly all of the male’s complex genital structures remain outside the female. Copulation behavior and genital morphology in Tipula (Triplicitipula) colei and T. (Lunatipula) translucida suggest that some male genital structures function to stimulate the female: male structures that contact the female bear tufts or dense arrays of modified setae on precisely the surfaces that contact the female; contact involves repeated, stereotyped rhythmic movements that include brushing, vibrating, scraping, and tapping; the movements are appropriately designed to utilize the morphology of the modified setae to stimulate the female; and the movements have little or no other perceptible mechanical effects on the female. The female structures contacted by these male genital movements fail to show the defensive designs predicted by the theories of genital evolution that are based on morphological species isolation or male–female morphological conflicts of interest; also unexplained by the conflict of interest hypothesis are female movements that seem designed to increase rather than avoid stimulation by the male.

Intersexual differentiation is crucial for the speciation and maintenance of dioecious plants, but the underlying mechanisms, including the genes involved, are still poorly understood. Here, we focused on a typical dioicous plant Morus alba, to explore the molecular footprints relevant to sex evolution by revealing the differentially expressed genes (DEGs) between two sexes and the testing signals of selection for these DEGs. From the results, we found a total of 1543 DEGs. Interestingly, 333 and 66 genes expression were detected only in male and female inflorescences, respectively. Using comparative transcriptomics, the expression of 841 genes were found to be significantly higher in male than in female inflorescences and were mainly enriched in defense-related pathways including the biosynthesis of phenylpropanoids, cutin, suberine and waxes. Meanwhile, the expression of 702 genes was female-biased and largely enriched in pathways related to growth and development, such as carbohydrate metabolism, auxin signaling and cellular responses. In addition, 16.7% and 17.6% signals of selection were significantly detected in female- and male-biased genes, respectively, suggesting their non-negligible role in evolution. Our findings expanded the understanding of the molecular basis of intersexual differentiation and contribute to further research on sex evolution in dioecious plants.

Abstract The male genitals of internal fertilisers evolve rapidly and divergently, and sexual selection is generally responsible for this. Many sexually selected traits are condition‐dependent—with their expression dependent upon the resources available to be allocated to them—as revealed by genetic or environmental manipulations of condition. However, it is not clear whether male genitals are also condition‐dependent. Here we manipulate condition in two ways (via inbreeding and diet) to test the condition‐dependence of the genital arch of Drosophila simulans. We found that genital size but not genital shape suffered from inbreeding depression, whereas genital size and shape were affected by dietary manipulation of condition. The differential effects of these treatments likely reflect underlying genetic architecture that has been shaped by past selection: inbreeding depression is only expected when traits have a history of directional selection, while diet impacts traits regardless of historical selection. Nonetheless, our results suggest genitals can be condition‐dependent like other sexually selected traits.

Abstract While sexual size dimorphism (SSD) is abundant in nature, there is huge variation in both the intensity and direction of SSD. SSD results from a combination of sexual selection for large male size, fecundity selection for large female size and ecological selection for either. In most vertebrates, it is variation in the intensity of male–male competition that primarily underlies variation in SSD. In this study, we test four hypotheses regarding the adaptive value of SSD in sharks—considering the potential for each of fecundity, sexual, ecological selection and reproductive mode as the primary driver of variation in SSD between species. We also estimate past macroevolutionary shifts in SSD direction/intensity through shark phylogeny. We were unable to find evidence of significant SSD in early sharks and hypothesise that SSD is a derived state in this clade, that has evolved independently of SSD observed in other vertebrates. Moreover, there is no significant relationship between SSD and fecundity, testes mass or oceanic depth in sharks. However, there is evidence to support previous speculation that reproductive mode is an important determinant of interspecific variation in SSD in sharks. This is significant as in most vertebrates sexual selection is thought to be the primary driver of SSD trends, with evidence for the role of fecundity selection in other clades being inconsistent at best. While the phylogenetic distribution of SSD among sharks is superficially similar to that observed in other vertebrate clades, the relative importance of selective pressures underlying its evolution appears to differ.

Abstract Life‐history theory predicts that reproductive investments are traded‐off against self‐maintenance. Telomeres, the protective caps on the ends of chromosomes, offer a promising avenue for assessing life‐history trade‐offs, as they shorten in response to stressors and are predictive of the remaining lifespan. In males, testosterone frequently mediates life‐history trade‐offs, in part, through its effects on sexual ornamentation, which is an important aspect of reproductive investment. However, studies of within‐individual associations between telomere dynamics and sexual ornamentation are limited in number and have produced mixed results. Furthermore, most such studies have been observational, making it difficult to discern the nature of any causal relationship. To address this, we used short‐acting testosterone implants in free‐living male superb fairy‐wrens (Malurus cyaneus) to stimulate the production of a sexual ornament: early moult into a costly blue breeding plumage. We found no evidence that elevated testosterone, and the consequent earlier moult into breeding plumage, accelerated telomere shortening. We therefore followed up with a systematic review and two meta‐analyses (28 studies, 54 effect sizes) exploring the associations between telomeres and (1) testosterone and (2) sexual ornamentation. In line with our experimental findings, neither meta‐analysis showed an overall correlation of testosterone or sexual ornamentation with telomere length or telomere dynamics. However, meta‐regression showed that experimental, compared to observational, studies reported greater evidence of trade‐offs. Our meta‐analyses highlight the need for further experimental studies to better understand potential responses of telomere length or telomere dynamics to testosterone or sexual ornamentation.

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

Both conspicuous plumage ornamentation and song are well‐known examples of sexually selected traits, but their interrelationship is not well known, perhaps in part because of confounding factors, including interspecific variation in ecology, habitat, morphology, and type of ornamentation. Here, using a phylogenetic comparative approach and the 69 species with available information (i.e. 96% of all 72 species), I examined the evolutionary relationship between forked tails and the presence/absence of song in hirundines (Aves: Hirundininae). Hirundines have similar ecology (e.g. aerial insectivores, social monogamy, and biparental provisioning), morphology (e.g. syrinx with nearly complete bronchial rings), and plumage ornamentation (i.e. a sexually selected forked tail), which provides a unique opportunity to examine the evolutionary associations between plumage ornamentation and song. In particular, hirundines have repeatedly lost their ornamentation, forked tails, setting up a condition to test their association with the evolutionary gain/loss of their simple song. After controlling for phylogeny and covariates, I demonstrated that song was less likely to be found in species with forkless tails than in species with forked tails. Two correlates of tail shape, sexual dimorphism in the overall plumage characteristics as a well‐known proxy of sexual selection and incubation type as a measure of extrapair mating opportunity, were not positively related to the presence or absence of song, indicating the importance of forked tails, rather than their correlates. The analysis of the correlated evolution of discrete characters further supported the correlated evolution of the two traits, in which forked tails and song are maintained together and less likely to be lost under the presence of each other. The current study provided macroevolutionary support for the integrated use of visual and acoustic courtship traits.

A morphological trait can have multiple functions shaped by varying selective forces. Bare parts in birds, such as wattles, casques and combs, are known to function in both signalling and thermoregulation. Studies have demonstrated such structures are targets of sexual selection via female choice in several species of Galliformes (junglefowl, turkeys and grouse), though other studies have shown some role in thermoregulation (guineafowl). Here, we tested fundamental hypotheses regarding the evolution and maintenance of bare parts in Galliformes. Using a phylogeny that included nearly 90% of species in the order, we evaluated the role of both sexual and natural selection in shaping the function of bare parts across different clades. We found a combination of both environmental and putative sexually selected traits strongly predicted the variation of bare parts for both males and females across Galliformes. When the analysis is restricted to the largest family, Phasianidae (pheasants, junglefowl and allies), sexually selected traits were the primary predictors of bare parts. Our results suggest that bare parts are important for both thermoregulation and sexual signalling across Galliformes but are primarily under strong sexual selection within the Phasianidae.

Sexual selection has long been thought to promote speciation, but this possibility still remains a topic of controversy. Many theoretical models have been developed to understand the relationship between sexual selection and speciation, but such relationship seems complex and sexual selection has also been argued to prevent speciation in many scenarios. Here, I model for the first time the tendency of speciation due to sexual selection using realistic model parameters input collected from an existing species, the jumping spider Hasarius adansoni. I show that, even though the species has substantial female variance in preference (the model typically thought to link sexual selection to speciation), when realistic parameters are input in the model, it predicts directional selection, rather than disruptive selection. I propose that including realistic parameters in speciation models is a new tool that will help us understand how common sexual selection helps or hinders speciation in the real world. [ABSTRACT FROM AUTHOR]

The evolution of conspicuous morphology and related displays is often ascribed to their role in sexual selection. The context of displays together with the phylogenetic sequence of morphological and behavioral innovations provides insight into their evolution. Do conspicuous features function in mate attraction and/or aggression and does a behavioral display evolve before or after the morphological feature most evident in the display? These questions were explored for a unique display and dorsal fin feature in a clade of blenniiform fishes for which both courtship and aggressive displays are known. The anterior dorsal-fin spines of the Spikefin Blenny, Coralliozetus rosenblatti, are elongate. It has a unique courtship display but the fin is held statically erect similar to congeners. This and other species of Coralliozetus, perform a unique aggressive display, the "fin flag", in which the anterior dorsal fin is waved laterally when encountering conspecifics. The spike-like dorsal fin of C. rosenblatti and its exaggerated lateral movements render this display especially conspicuous. In addition, it performs the fin flag more than twice as often as congeners. Thus, the dorsal fin of the Spikefin Blenny evolved to amplify an extant aggressive display consistent with the behavioral drive hypothesis that posits behavior leads to subsequent morphological evolution making displays more effective. [ABSTRACT FROM AUTHOR]

Island environments have the potential to change evolutionary trajectories of morphological traits in species relative to their mainland counterparts due to habitat and resource differences, or by reductions in the intensity of social or sexual selection. Latitude, island size, and isolation may further influence trait evolution through biases in colonization rates. We used a global dataset of passerine plumage color as a model group to identify selective pressures driving morphological evolution of island animals using phylogenetically-controlled analyses. We calculated chromaticity values from red and blue scores extracted from images of the majority of Passeriformes and tested these against the factors hypothesized to influence color evolution. In contrast to predictions based on sexual and social selection theory, we found consistent changes in island female color (lower red and higher blue chromaticity), but no change in males. Instead, island size and distance from mainland and other islands influenced color in both sexes, reinforcing the importance of island physiognomy in shaping evolutionary processes. Interactions between ecological factors and latitude also consistently influenced color for both sexes, supporting a latitudinal gradient hypothesis. Finally, patterns of color evolution varied among families, indicating taxon-specific microevolutionary processes in driving color evolution. Our results show island residency influences color evolution differently between sexes, but the patterns in both sexes are tempered by ecological, island characteristics, and phylogenetic effects that further vary in their importance among families. The key role of environmental factors in shaping bird plumage on islands further suggests a reduced importance of sexual and social factors in driving color evolution. [ABSTRACT FROM AUTHOR]

Emitting conspicuous signals into the environment to attract mates comes with the increased risk of interception by eavesdropping enemies. As a defence, a commonly described strategy is for signallers to group together in leks, diluting each individual's risk. Lekking systems are often highly social settings in which competing males dynamically alter their signalling behaviour to attract mates. Thus, signalling at the lek requires navigating fluctuations in risk, competition and reproductive opportunities. Here, we investigate how behavioural defence strategies directed at an eavesdropping enemy have cascading effects across the communication network. We investigated these behaviours in the túngara frog (Engystomops pustulosus), examining how a calling male's swatting defence directed at frog-biting midges indirectly affects the calling behaviour of his rival. We found that the rival responds to swat-induced water ripples by increasing his call rate and complexity. Then, performing phonotaxis experiments, we found that eavesdropping fringe-lipped bats (Trachops cirrhosus) do not exhibit a preference for a swatting male compared to his rival, but females strongly prefer the rival male. Defences to minimize attacks from eavesdroppers thus shift the mate competition landscape in favour of rival males. By modulating the attractiveness of signalling prey to female receivers, we posit that eavesdropping micropredators likely have an unappreciated impact on the ecology and evolution of sexual communication systems. [ABSTRACT FROM AUTHOR]

An analytical review of scientific publications containing materials or discussion of the concept of sexually selective infanticide (SSI) in brown bear populations (Ursus arctos) is presented. The authors of the SSI concept refer to the idea of sexual selection, which is a rather shaky conceptual basis. The concept was formed largely on the basis of materials obtained during the study of intraspecific relations in lion populations (Panthera leo). However, facts regarding the behavioral ecology of the lion, which accumulate relatively quickly, can be interpreted quite ambiguously and even only when applied to this species, the concept of this does not look convincing enough and is obviously unnecessarily anthropomorphic. Infanticide, cannibalism, and their combination are recorded in both lion and brown bear populations. However, the behavioral ecology of these species differs significantly. Brown bear populations are characterized by pronounced seasonality of reproduction; the presence of a reproductive interval in bear females, which can vary significantly in populations with different habitat conditions and varies from 1 to 5 years; and mating patterns than can vary from lax monogamy to panmixia. Multiple paternity is possible within the same litter of cubs of a brown bear. It follows from the review that brown bear populations are characterized by many features of sociality, with the lifestyle of bears being both solitary and group. It is hardly correct to classify the brown bear (and other species of bears) as uniquely asocial. From the analysis of publications on the behavioral ecology of the brown bear, it follows that the application of the SSI concept without significant additions is hardly useful for understanding the intraspecific relations of this species. [ABSTRACT FROM AUTHOR]

Sexual dimorphism typically arises as a result of sexual selection or sex-specific natural selection. Species that exhibit cryptic coloration provide an excellent system for studying sex-specific selection for sexual dichromatism. In this study, we examined the sexually dichromatic use of chromatophores in the seawhip shrimp, Neopontonides beaufortensis (Borradaile, 1920), which commonly resides on colonies of Leptogorgia virgulata (Lamarck, 1815), a gorgonian octocoral that occurs in multiple color morphs. We documented the frequency of cryptic coloration in N. beaufortensis and tested colony color preference in relation to their current color. In the field, individuals always matched the color of the L. virgulata colony they were found on or were largely translucent. However, when given a choice, individuals chose colonies at random, independent of color. Additionally, we quantified locations across the bodies of males and females that differ most in chromatophore usage and tested the ability of both sexes to change color over 7 days. Females housed with L. virgulata colonies that differed in color from their starting color changed their coloration over the 7 days to better match the colony, while males remained translucent regardless of the color of colony they were housed with. Neopontonides beaufortensis individuals differed most in their coloration in regions corresponding to the saddle region and areas of the abdomen, locations in which females carry their eggs during development. These findings provide insight into the ecological factors underlying sexual dichromatism and shed light on the potential sex-specific selective mechanisms responsible for sexually dimorphic traits. [ABSTRACT FROM AUTHOR]

Integument colouration can influence many aspects of fitness, and is under strong sexual selection. Amphibians often express sexual dichromatism, and ultra-violet (UV) colouration is usually biased toward males as a sexual signal. As an honest signal, colouration is related to several individual traits, but can also be related to environmental factors such as anthropogenic pollutants, to which amphibians are highly sensitive. In this study, we investigated sexual dichromatism and UV reflectance covering a large visual spectrum (wavelength ranging from 300 to 700 nm) on different body areas (throat, ventral and dorsal areas), in a widespread amphibian species, the spiny toad (Bufo spinosus). Then, we tested the impact of chronic exposure to two widespread herbicides (glyphosate's primary metabolite [AMPA] and Nicosulfuron) on their colouration. We found a strong but unexpected sexual dichromatism with females reflecting more in the UV spectrum (throat and ventral area) than males, suggesting these body parts might be critical in intra-specific signalling. Females with higher ventral UV reflectance were in better body condition, suggesting an honest signal role of UV reflectance which could influence male choice. Throat colouration was further differentially influenced by agrochemicals according to sexes. In AMPA-exposed males, throat was more saturated in yellow-orange than in control males, and Nicosulfuron exposure decreased the throat's reflectance hue in females, which can bear consequences on mate attractiveness. Future studies need to investigate the underlying mechanisms that are altered by agrochemical exposure. [ABSTRACT FROM AUTHOR]

Parasite-mediated sexual selection has been the topic of extensive research and enthusiastic debate for more than three decades. Here, we suggest that secondary sexual characters may not only signal parasite resistance but also defensive tolerance. We exemplify this possibility by analysing information on two sexually selected traits, annual reproductive success, and ectoparasitism in a barn swallow Hirundo rustica population followed for more than 30 years. For each individual, we estimated the slope of the association between reproductive success and parasitism as an index of tolerance and subsequently explored the association with the expression of the sexually selected traits. In accordance with expectations of parasites playing a role in sexual selection, tail length was negatively related to load of chewing lice and nest size was positively related to tolerance to chewing lice. We discuss the importance of considering defensive tolerance for understanding the role of parasite-mediated sexual selection. [ABSTRACT FROM AUTHOR]

Livebearing fishes are a common model for studying the effects of predation on prey biology. Numerous studies have found differences in life history, sexual selection, behavior, and morphology between populations of the same species that co‐occur with predators and those that do not. Alfaro cultratus is a livebearing fish with populations in different predation environments, but unlike other livebearers, this species also has an extreme body shape that is laterally compressed. Given this unusual morphology, we asked if predation environment would still predict overall body shape, as has been documented in other species. We collected specimens from both predator and no predator sites in Costa Rica and used a geometric morphometrics analysis to determine if body shape is affected by predation environment, while controlling for size and river gradient. Body shape does indeed differ between predation environments; however, the observed differences contrast with the patterns found in other livebearer systems. Alfaro cultratus in predation environments had deeper and shorter bodies and deeper caudal peduncles than those found in environments without dominant fish predators. [ABSTRACT FROM AUTHOR]

There is a growing effort to understand how sexual selection varies over space and time under different ecological conditions and how this can maintain variation in sexual traits. An interesting ecological condition is population density, which can either increase or decrease sexual selection depending on the natural history of the species. We examined sexual and natural selection in an undescribed amphipod species (Hyalella sp.) using surveys of two natural populations that increase in density from spring to summer. We also conducted an experiment that directly manipulated density to assess the effects on sexual selection. In the field during spring (low density) and summer (high density), we documented sexual selection on male traits, including body size, gnathopods and antennae. We found that the magnitude and direction of this selection changed from spring to summer and that selection patterns differed between populations. In the experiment, we found no sexual selection occurred at low density, but found significant positive selection on all three male traits at medium and high densities. These results underline the importance of isolating individual ecological factors to determine their role in sexual selection while also documenting patterns in natural populations to understand how selection varies over space and time. [ABSTRACT FROM AUTHOR]

This document is a collection of abstracts from the International Journal of Psychology, covering various topics related to psychology and human behavior. The abstracts discuss subjects such as the role of odor perception in social interactions, the evolutionary function of jealousy, the influence of nonverbal behavior on human sexuality, the impact of sexual selection on human morphology and mate preferences, the relationship between smell and sexuality, the role of olfactory conditioning in mate choice in rats, the similarity of body odor between partners and parents, the influence of olfactory disgust on sexual arousal in men, the relationship between sexual function, sense of smell, and depressive tendencies in young women, the evolution of social norms, and the effect of competition outcome on body odor quality. One specific study in the collection focuses on women's preference for low masculine voices in the Chinese culture, finding that women generally preferred lower pitched voices, with women in long-term relationships having a stronger preference, especially when at a high risk of pregnancy. [Extracted from the article]

Sexual dimorphism in lizards is broadly attributed to intrasexual differences in morphology that affect fitness. In the lizard family Cordylidae, commonly known as girdled lizards, sexual dimorphism is common. Differences in morphological traits (e.g., body and head size) between females and males are useful for describing sexual dimorphism, and examining other traits (e.g., scar frequencies and color) is useful for understanding the selective pressures driving sexual dimorphism in cordylids. Recent morphological studies in Cordylidae reveal sexual dimorphic biases where males have larger heads, but either sex may have larger bodies. In this study, we examined body size, head dimensions, and other traits that commonly differ between sexes to identify sexually dimorphic traits and understand selective pressures in the Namibian endemic cordylid Namazonurus pustulatus (Herero Nama Lizard). We measured 224 field and 10 museum specimens within the known distribution of N. pustulatus. Our results indicate that females were larger in snout–vent length (SVL), axilla-to-groin length, and mass, but males were larger in head width and head length. Allometric growth in juvenile head dimensions was greater than that in adults. Segmented regression analyses indicated a change in growth rate of approximately 68.3–70.0 mm SVL, which we associated with sexual maturity. Adults of both sexes were larger at low elevations (1200–1700 m above sea level) than adults at high elevations (2000–2500 m above sea level), but there was no difference in head height. Epidermal glands (generation glands and femoral pores) scaled with SVL. No differences in scar frequencies were identified, but frequencies were higher than any other cordylid species recorded to date. We attributed larger female size to fecundity selection and larger male head size to sexual selection. This work establishes the first detailed biometric characteristics of the species, fills the missing literature gap of sexual dimorphism information from a species in the Namazonurus clade, and is the first to examine sexual dimorphism in a Namibian endemic cordylid. [ABSTRACT FROM AUTHOR]

Canthariphilous species are those arthropods attracted to cantharidin (CTD), a defensive compound produced by two beetle families (Meloidae and Oedemeridae). Although several species are known to be attracted to CTD, canthariphily was recently discovered in new species, suggesting that the list of canthariphilous species is still far from being complete. A systematic sampling focused to detect canthariphilous species has never been performed in Italy. The present research provides a list of seven canthariphilous species (Diptera: Ceratopogonidae, Anthomyiidae; Coleoptera: Anthicidae) from the Tolfa Mountains (Latium, Central Italy) resulting from a one-year sampling with CTD-baited and control traps. New species (Atrichopogon atriscapulus and A. tolfensis) were found to be attracted to CTD, and other species, already known as canthariphilous, were recorded for the first time in the Italian fauna (A. atriscapulus and A. meloesugans). A new scenario about the ecological significance of CTD in the sexual selection of canthariphilous species was speculated in A. meloesugans. Finally, a list of CTD-producing species occurring in the sample area was provided to suggest putative natural CTD sources. [ABSTRACT FROM AUTHOR]

Stabilizing selection provides a challenge to molecular population genetics. Although stabilizing selection is ubiquitous, its genomic signature is difficult to distinguish from demographic signals. Experimental evolution provides a promising approach to characterize genomic regions exposed to stabilizing selection. A recent experimental evolution study of Aedes aegypti populations evolving either with or without sexual selection found a pattern of genetic differentiation suggestive of relaxed stabilizing selection. I argue that this study could not have detected the signal of relaxed stabilizing selection. I highlight why incorrect statistical methods resulted in a high number of false positive candidate single nucleotide polymorphism (SNPs) and discuss the fallacy of functional validation of candidate SNPs for polygenic traits by RNA-mediated knockdown. [ABSTRACT FROM AUTHOR]

Pheromones mediate species-level communication in the search for mates, nesting, and feeding sites. Although the role of pheromones has long been discussed by various authors, their existence was not proven until the mid-twentieth century when the first sex pheromone was identified. From this finding, much has been speculated about whether this communication mechanism has acted as a regulatory agent in the process of speciation, competition, and sexual selection since it acts as an intraspecific barrier. Chrysomelidae is one of the major Phytophaga lineages, with approximately 40,000 species. Due to this immense diversity the internal relationships remain unstable when analyzed only with morphological data, consequently recent efforts have been directed to molecular analyses to establish clarity for the relationships and found their respective monophyly. Therefore, our goals are twofold 1) to synthesize the current literature on Chrysomelidae sex pheromones and 2) to test whether Chrysomelidae sex pheromones and their chemical structures could be used in phylogenetic analysis for the group. The results show that, although this is the first analysis in Chrysomelidae to use pheromones as a phylogenetic character, much can be observed in agreement with previous analyses, thus confirming that pheromones, when known in their entirety within lineages, can be used as characters in phylogenetic analyses, bringing elucidation to the relationships and evolution of organisms. [ABSTRACT FROM AUTHOR]

The colourful plumages of weaverbirds (family Ploceidae, with 118 species recognised) provide a well-known and in part iconic showcase of sexual selection, with widespread sexual dimorphism (93 species) as well as seasonal dimorphism (62 species). The tremendous diversity in both the type and degree of plumage dimorphism is poorly known, which calls for a better and extended understanding of the highly variable moult patterns in this group. Here, we lay a foundation for this by reviewing and discussing what is known of the timings and patterns of moult in the Ploceidae. The extent of post-juvenile moult is poorly known in weavers: it is known to be complete in 10 species, partial in two species, and either complete or partial in six species. However, it is likely that there is more variation than previously thought. Weavers typically have a complete moult after breeding, and before breeding a partial prenuptial moult, restoring the male (and, in some species, female) breeding plumage; this usually involves only body feathering, one exception being the Seychelles Fody Foudia sechellarum, which has a complete prenuptial moult. We compiled primary moult data based on the proportion of feather mass grown, for 11 weaver species, three of which are newly reported on. Timing of primary moult is discussed in relation to sex, location and annual timing. The duration of primary moult varies widely between and within species, from 46 days (1.5 months) in a widowbird to 215 days (7 months) in an arid species. Weavers in arid regions have longer moult durations than weavers in other regions. Examples of the overlap of primary moult and breeding are presented. [ABSTRACT FROM AUTHOR]

Reproductive traits are central to organismal fitness, and so the factors influencing patterns of reproduction and offspring survival are at the heart of biology. Making use of breeding data collected over 16 years at the King Khalid Wildlife Research Centre in Saudi Arabia, we investigated the reproductive biology of Arabian gazelles Gazella arabica. Offspring survival was mainly a function of birth weight, with heavier offspring having higher survival rates than lighter offspring. However, while sons were heavier than daughters, daughters had higher survival rates. We could not find evidence that giving birth to sons negatively impacts offspring weight in the following year. We uncovered large narrow-sense heritability (h 2) in offspring weight at birth, while maternal effects (m 2) on birth weight were of lesser importance. However, maternal effects on offspring survival were strong until weaning age, while paternal effects dominated survival to sexual maturity and first reproduction. We propose that variation in maternal postnatal care might overshadow the effects of maternal inheritance of birth weights, while the overall strong heritability of weight at birth and the paternal effects on survival illustrates strong variance in sire fitness based on genetic quality, suggesting a role for sexual selection by female mate choice in wild populations. [ABSTRACT FROM AUTHOR]

In many animals, body size is correlated with reproductive success. Selection sometimes generates striking differences in body size between males and females (i.e. sexual size dimorphism, SSD). SSD is common in spiders (Araneae), and is typically explained by selection for larger, more fecund females and rapidly maturing, and consequently smaller, males. Within a species males and females also often vary in body size. In the false widow spider, Steatoda grossa , females are larger than males and males trade body size for rapid development and early maturation. Moreover, males vary considerably in body size, suggesting that under certain conditions there may be advantages to large size. Here, we tested the role of male body size on mating success under noncompetitive and competitive mating conditions (i.e. male–male competition) in S. grossa. We found that body size did not influence mating success or copulation duration under noncompetitive conditions, but that larger males were more successful at obtaining access to females under competitive mating conditions. Additionally, we found that total copulation duration was significantly lower when a rival male was present. Our results show a large male advantage under male–male competition, which we suggest may contribute to the high variation in male body size observed in S. grossa. We further suggest that the reduced copulation duration observed under competitive mating conditions may have potential ramifications for male and female reproductive success and we discuss how patterns of selection acting on male body size might limit the extent of SSD in this species. • Male body size is important for mating success in many species. • Steatoda grossa males obtain mating success regardless of body size. • Under competitive conditions, larger males had greater mating success. • Female copulation duration was reduced in the presence of a male competitor. • The results offer insight into male body size evolution and sexual size dimorphism. [ABSTRACT FROM AUTHOR]

Even as numerous studies have documented that the red and yellow coloration resulting from the deposition of carotenoids serves as an honest signal of condition, the evolution of condition dependency is contentious. The resource trade‐off hypothesis proposes that condition‐dependent honest signalling relies on a trade‐off of resources between ornamental display and body maintenance. By this model, condition dependency can evolve through selection for a re‐allocation of resources to promote ornament expression. By contrast, the index hypothesis proposes that selection focuses mate choice on carotenoid coloration that is inherently condition dependent because production of such coloration is inexorably tied to vital cellular processes. These hypotheses for the origins of condition dependency make strongly contrasting and testable predictions about ornamental traits. To assess these two models, we review the mechanisms of production of carotenoids, patterns of condition dependency involving different classes of carotenoids, and patterns of behavioural responses to carotenoid coloration. We review evidence that traits can be condition dependent without the influence of sexual selection and that novel traits can show condition‐dependent expression as soon as they appear in a population, without the possibility of sexual selection. We conclude by highlighting new opportunities for studying condition‐dependent signalling made possible by genetic manipulation and expression of ornamental traits in synthetic biological systems. [ABSTRACT FROM AUTHOR]

Sexual selection is considered one of the key processes that contribute to the emergence of new species. While the connection between sexual selection and speciation has been supported by comparative studies, the mechanisms that mediate this connection remain unresolved, especially in plants. Similarly, it is not clear how speciation processes within plant populations translate into large‐scale speciation dynamics. Here, we review the mechanisms through which sexual selection, pollination, and mate choice unfold and interact, and how they may ultimately produce reproductive isolation in plants. We also overview reproductive strategies that might influence sexual selection in plants and illustrate how functional traits might connect speciation at the population level (population differentiation, evolution of reproductive barriers; i.e. microevolution) with evolution above the species level (macroevolution). We also identify outstanding questions in the field, and suitable data and tools for their resolution. Altogether, this effort motivates further research focused on plants, which might potentially broaden our general understanding of speciation by sexual selection, a major concept in evolutionary biology. [ABSTRACT FROM AUTHOR]

Male genitalia are rapidly evolving structures, often driven by sexual selection to increase fertilisation success. Although sexual selection on females can be strong in systems where males provide offspring care or feed their mates, sometimes resulting in the evolution of female ornamentation, there are no actual estimates of direct sexual selection on female genitalia. In a New Zealand ground weta, Hemiandrus pallitarsis (Orthoptera: Ensifera, Anostostomatidae), females possess a genitalic device (the accessory organ) that is necessary for successful copulation and the acquisition of glandular food-gifts from males. These nutritious gifts are known to result in sexual competition among females in other ensiferan species. In ground weta, the gifts are probably important in avoiding starvation during a months-long period when caring for (their lifetime production of) eggs and offspring. Here, we test the hypothesis that the accessory organ is a sexually selected device in H. pallitarsis by measuring the female Bateman gradient, Jones index, and directional sexual selection on the accessory organ. Using newly developed and characterised microsatellite loci, we analyse offspring and/or stored sperm to estimate female mating frequency for the first time in ground weta. As predicted, we found both a positive Bateman gradient and Jones index for females, and evidence of directional sexual selection on accessory organ length. Although organ length does not correlate well with female fecundity, it may increase mating success by indicating her condition and thus quality of her offspring care. Significance statement: Female genitalia have largely been studied in the context of exerting selection on males, while the potential for selection on females via mate acquisition or manipulation of males is virtually unstudied. Such selection may be relevant in systems where males make investments in reproduction (offspring-care; mate-feeding), and females are subject to strong sexual selection, occasionally possessing sexual ornaments. Using microsatellite analysis of offspring and stored sperm to estimate mating frequency, we provide the first evidence of directional sexual selection on a female genital device (accessory organ) found in species of maternal care-providing ground weta. In our focal species, Hemiandrus pallitarsis, we found that females with more mates produced more offspring and females with longer accessory organs obtained more mates. These findings suggest that the female genital device is a secondary sexual trait, although may have additional mechanical functions. [ABSTRACT FROM AUTHOR]

Avian plumage coloration could be altered by external factors like dust accumulation, but the effect of environmental conditions on such post-moult colour changes are poorly studied. Here, we investigated how exposure to the atmosphere in habitats of differing anthropogenic pressures modifies UV/blue structural plumage coloration — a sexually selected trait in eastern bluebirds Sialia sialis. We collected feather samples from live birds and distributed them in three types of habitats: (i) urban roads with low traffic, (ii) urban roads with high traffic, and (iii) rural roads with low traffic. After 4 weeks, the brightness of feathers decreased in all types of habitats-resulting in less-ornamented coloration. Changes in UV and blue chroma, however, varied with habitat type; chroma decreased in urban areas (becoming less ornamented), but increased in rural locations (becoming more ornamented). According to physiological models of avian colour vision, however, these changes in coloration tended to be below perceptual thresholds. Our results underscore the importance of how human activity can influence plumage colour of individual birds during the period between moult cycles which could have an impact on avian visual signalling. The study opens venues for further studies focusing on how the optical properties of specific airborne particles can influence coloration of wild-living animals. Significance statement: Plumage coloration plays an important role in avian visual communication. In addition to moult-based change, coloration may change between moult cycles due to exposure to external factors like, for example, dust accumulation. Ecological factors modifying a passive plumage change, however, remains poorly studied. We collected samples of structurally coloured feather from a species wherein plumage colour is sexually selected and exposed them to outdoor conditions. We demonstrate that UV/blue chroma of coloration changes differently in urban and rural habitats. It increased in rural and decreased in urban areas. On the other hand, brightness decreased in both habitat types. Using physiological models of avian colour vision, however, we found that these colour changes were likely not perceptible to birds. Our study provides the first evidence that changes in coloration of fully grown feathers may be habitat dependent. [ABSTRACT FROM AUTHOR]

Placentotrophy is a particular type of maternal provisioning to developing embryos, in which mothers actively provide nutrients via complex placental structures. Placentotrophy implies less pre-fertilization investment, resulting in a shift from pre- to post-copulatory sexual selection. This change can potentially result in a conflict between females and males. This phenomenon has been demonstrated at the interspecific level in viviparous fishes of the family Poeciliidae, in which males of species that lack placentotrophy have evolved traits related to pre-copulatory sexual selection such as coloration, ornaments, and courtship behavior. Placentotrophic species, on the other hand, have evolved traits associated with post-copulatory sexual selection such as long intromittent organs (gonopodium) and increased sexual coercion behavior. Here we test, for the first time at the intraspecific level, whether there is a similar relationship between a higher degree of female placentotrophy and the evolution of male reproductive traits (larger testes and longer gonopodia) in three species of the genus Poeciliopsis (P. gracilis, P. infans, and P. prolifica). We observed a tendency towards longer gonopodia in males of P. gracilis as well as the largest testes of P. prolifica males in the populations with the highest degrees of placentotrophy. However, the statistical support for these findings was relatively weak. Therefore, we failed to support the hypothesis of a selective effect of female placentotrophy on male gonads and genitalia. We discuss other evolutionary forces that may have driven the observed intraspecific variation in male reproductive traits of Poeciliopsis fishes. [ABSTRACT FROM AUTHOR]

The Sakhalin pine sawyer Monochamus saltuarius (Gebler) (Coleoptera: Cerambycidae) is a new vector of pine wood nematode in China, which has caused huge economic losses in the forestry industry. The mating process of M. saltuarius has been described in detail. However, mate choice and sexual selection in this species are not fully understood. In this study, we quantitatively evaluated the characteristics associated with contact between the sexes in mating and inferred the sex-specific characteristics under selection. We detected positive correlations between the morphological characteristics of females and males. Most female traits and all male traits differed significantly between mated and unmated individuals. The results of this study provide evidence for the selection of the mating preferences in M. saltuarius. [ABSTRACT FROM AUTHOR]

As fiddler crabs increase in size, closing force weakens proportionally because claw growth is not isometric. As a result, mechanical advantage decreases at the tip with increasing claw length. Closing force at an interior tubercle is greater at the tip, and a previous study of two species claimed evidence for compensation by relative movement of tubercles toward the hinge as size increases. I reconsidered this hypothesis with a biometric analysis of eight species from five genera and all three major biogeographic regions. I tested test two null hypotheses: 1) as claw length increases, mechanical advantage did not increase at the tubercle, relative to the claw tip, and 2) closing force did not increase at the tubercle, relative to the claw tip, as claw size increased. Both null hypotheses are largely supported, which in turn supports the weakening combatant hypothesis. In all cases, log force as a function of log claw length at an interior tubercle is 1.40, which is less than 2, the slope value expected if there was complete compensation. This is only slightly greater than the slope at the dactyl tip, which is 1.21. Thus, as a fiddler crab gets larger, with an incremental increase of claw length its closing force proportionally decreases, supporting the idea of a weakening combatant. But it gains a large showy claw with relatively narrow pincers and relatively less mass required to swing around while waving. This is indeed a beautiful weapon, but not for sheer closing force. [ABSTRACT FROM AUTHOR]

Sexual size dimorphism (SSD) is a common phenomenon across the animal kingdom. Mammals are unusual in primarily displaying male-biased SSD, where males of a species are typically larger than females. The driving factors behind the evolution of this SSD have been much debated, with popular hypotheses invoking the influence of mating system and social organization via sexual selection, dietary niche divergence and broad-scale correlations with body size (Rensch's rule). Here, we investigate the macroevolutionary origins and maintenance of SSD among mammals, using phylogenetic general mixed linear models and a comprehensive global dataset to evaluate correlations of diet, body mass, seasonality, social organization and mating system with SSD type. We find that SSD as a whole is lost at a greater rate than it is gained, with female-biased SSD being particularly unstable. Non-monogamous mating systems, vertebrate prey consumption and temperature seasonality correlate with male-biased SSD, while polyandry correlates with female-biased SSD, and both types of SSD are positively correlated with body mass. This is in partial contrast to the predictions of Rensch's rule, which predicts that female-biased SSD would correlate negatively with body size. Taken together, our results highlight the importance of considering multiple ecological and social drivers when evaluating the macroevolutionary trajectory of sex differences in body size. [ABSTRACT FROM AUTHOR]

Desynchrony of phenological responses to climate change is a major concern for ecological communities. Potential uncoupling between one of the most fundamental divisions within populations, males and females, has not been well studied. To address this gap, we examined sex-specific plasticity in hibernation phenology in two populations of Columbian ground squirrels (Urocitellus columbianus). We find that both sexes display similar phenological plasticity to spring snowmelt dates in their timing of torpor termination and behavioural emergence from hibernation. As a result of this plasticity, the degree of protandry (i.e. males' emergences from hibernation preceding those of females) did not change significantly over the 27-year study. Earlier male behavioural emergence, relative to females, improved the likelihood of securing a breeding territory and increased annual reproductive success. Sexual selection favouring earlier male emergence from hibernation may maintain protandry in this population, but did not contribute to further advances in male phenology. Together, our results provide evidence that the sexes should remain synchronized, at least in response to the weather variation investigated here, and further support the role of sexual selection in the evolution of protandry in sexually reproducing organisms. [ABSTRACT FROM AUTHOR]