Sexual Traits Research Articles

Multimodal signalling in manakins: lack of correlated evolution between acoustic, visual and behavioural traits

Sexual traits, such as visual adornments, sound‐based cues and courtship dances, are frequently displayed in combination as multimodal signals. Some hypotheses propose that different signals trade‐off with each other, potentially due to resource limitations (‘trade‐off’ or transfer hypothesis) or that these develop simultaneously to enhance communication effectiveness (‘joint evolution’ hypothesis). Alternatively, multiple cues may evolve independently to serve distinct functions or convey different information (‘multiple messages’ hypothesis). Here, we explored the interdependence between different signal modalities in manakins (Pipridae), which are known for great interspecific diversity in the degree of elaboration in courtship dance, song and plumage coloration. We also used comparative methods to explore the mode of evolution and the degree of conservatism of these signals. We found that song, plumage coloration and courtship dance evolved independently as there was no correlation between these traits. Song evolution in manakins was attracted to a single optimum and exhibited a weak phylogenetic signal in comparison with those of colour and behavioural diversity. The high support found for the speciational and κ models when analysing the multivariate estimates of trait variability suggests that these signals (especially colour and behaviour attributes) may have evolved in a punctuated manner, with large evolutionary changes at speciation events and minimal subsequent changes along the branches. Our results show that song, colour and dance diversity are each associated (or marginally associated) with different ecological factors, indicating that sexual signals in manakins might convey different information and/or respond to different selection pressures. Larger species and those with lower dispersal capacity tend to exhibit higher colour richness, which in turn differed among lek categories, being higher in species with ‘classic’ leks and lower in non‐lekking species. Overall, the present study supports the idea that correlation between signal modalities does not constitute a widespread pattern in songbirds.

Predation affects the evolution of sex-specific longevity

Predation, a major cause of natural selection, is classically thought to target the weak and sick. However, predators can target animals with condition-dependent sexual traits, and therefore, high-quality individuals can also be the focus of predation. Thus, it is not always clear which individuals are the foci of predators or how this affects trait evolution. Here, we tested for evolutionary effects of sex-specific predation on male and female longevity using replicate populations of the broad-horned flour beetle Gnatocerus cornutus . We found that male-limited predation resulted in the evolution of reduced male and increased female longevity, while female-limited predation had no effects on the longevity of either sex. We also document the costs of reproduction. Coupled with other findings, our results suggest that predation impacts high-quality males and, because of negative intersexual genetic correlations, this increases female longevity.

Patterns of a sexually selected trait are not predictable across urban and non-urban populations of a songbird, the dark-eyed junco

Urbanization can result in novel selective pressures that can cause phenotypic differences amongst urban-tolerant species across urban and non-urban habitats. Here, we compared the size of the white tail patch (“tail white”), a sexual signaling trait, in two urban populations of dark-eyed juncos in comparison to neighboring non-urban populations. Contrary to our expectations, urban phenotypes did not differ from local wildlands in San Diego and Los Angeles counties in similar directions. While the San Diego population showed lower tail white compared to its neighboring wildland population, the Los Angeles population did not. The tail white of the Los Angeles population was not statistically different from that of the San Diego population, suggesting that urban populations may share similar environmental conditions yet face different selective clines due to urbanization. There were, however, differences between wildland populations. Differences in evolutionary histories, environmental conditions, and selective pressures within and outside urban areas may affect how urbanization facilitates population differentiation, even across urban populations of the same species.

Profile of Medico-legal Age Estimation Cases in a Tertiary Hospital in Kathmandu

Introduction: Medico-legal age estimation is the estimation of chronological age of an individual which is based upon analysis of physical development of the body, development of secondary sexual traits, tooth eruption, appearance of ossification centers of bones, and the degree of epiphyseal union. Chronological age of the subject whether a minor (less than 18 years) or an adult determines the fate of the case in the court of law. Objective: The present study revealed varied profiles of the perpetrator and the victim who came for medico-legal age estimation. Methods: This is a retrospective, descriptive cross-sectional study conducted in the Department of Forensic Medicine, Maharajgunj Medical Campus, Institute of Medicine (IoM). The data of medico-legal age estimation of 5 years period was analyzed using the statistical software SPSS 20. Results: Total of 313 individuals were studied. Majority of the individuals were within the age group of 16-17 years. Males (70.3 %) outnumbered females (29.7 %). Theft (31.9 %) was common among subjects, followed by sexual assault (18.2 %) and majority of subjects (59.7%) came from Province 3. Sixty percent of the subject’s alleged age, matched the estimated ages. Conclusion: This study shows the status of children in crime which demands attention of concerned authority. Males were significantly involved in theft and females were victims of sexual assault. Forty percent of the alleged age given by the subject differed from the estimated age, to change the fate of the case. These results could greatly benefit the judiciary system of Nepal.

Variability in Precipitation Weakens Sexual Selection for Nuptial Gifts in Spiders.

AbstractEnvironmental conditions (i.e., climatic variation) can strongly influence the cost and benefits of reproductive traits. Yet there is still no consensus on whether changing environmental conditions strengthen or relax sexual selection. Evidence from the literature suggests that highly variable environments can limit mate choice and investment in sexual traits, hence relaxing sexual selection pressures. Here, we tested this hypothesis using the nuptial gift-giving spider Paratrechalea ornata, in which males can either wrap nutritive (fresh prey) or worthless (prey leftovers) items in silk. We examined changes in males' sexual trait and female choice among six populations living under different climatic conditions. We found that large variation in precipitation limits female choice, potentially favoring the spread of deceptive worthless gifts. In populations under highly variable conditions and with the highest frequencies of worthless gifts (70%), males offering such gifts acquire longer mating durations than those offering nutritive gifts. In contrast, in populations with less variable conditions and the lowest frequencies of worthless gift (36%), females shortened mating duration to males offering worthless gifts. Our findings are consistent with the prediction that highly variable environmental conditions relax sexual selection.

Male Reproductive Traits Display Increased Phenotypic Variation in Response to Resource Quality and Parental Provisioning in a Tropical Rainforest Dung Beetle, Onthophagus c.f. babirussa.

Reproductive traits that mediate differential fitness associated with mate acquisition and fertilisation success are often strongly linked to the overall condition. We investigated the effects of resource quality and parental provisioning in the phenotypic expression of sexual and non-sexual traits in a rainforest dung beetle, Onthophagus c.f. babirussa (Eschscholtz, 1822) from Singapore. F1 individuals were reared from wild-caught beetles and paired up to produce offspring (F2), and F2 larvae from the same F1 parents were reared on two dung substrates (herbivore and omnivore) in a full-sib design. Sexual traits displayed greater phenotypic variation in response to dung resource quality, with the precopulatory trait (horn length) responding more than the postcopulatory trait (testes weight). Notably, genotype-by-environment interactions between parental lines (genotype) and dung type (environment) affected male body size and horn length only, suggesting sex-specific variance in plasticity associated with sexually selected precopulatory traits. Dung type had significant effects on all measured traits. Offspring that were provisioned higher quality resource (omnivore dung) had larger absolute and relative trait values. Parental lines only significantly affected female body size but none of the male traits, suggesting an important role of environment and resource partitioning in determining precopulatory success of male offspring. Parental provisioning of larval resource varied with resource quality and brood sequence. Parents provisioned more dung when herbivore dung was presented than when they were given omnivore dung and provisioned more dung for their earlier broods when using herbivore dung but not omnivore dung. This suggests a trade-off between early offspring fitness and resource quality. We tested directly for genotype-by-environment (G × E) interactions in the expression of several morphological traits relevant to dung beetle fitness and documented that offspring with similar phenotypes may result from completely different parental resource allocation strategies. We discuss the importance of studying parental investment on trait variation and its implications on dung beetle ecology.

Antler size in red deer: declining selection and increasing genetic variance with age, but little senescence.

While senescence is a common occurrence in wild populations, not all traits decline with age simultaneously and some do not show any senescence. A lack of senescence in secondary sexual traits is thought to be due to their importance for reproductive success. However, if reproductive success senesces, why would secondary sexual traits apparently not senesce? Here, we explored this question in a wild population of red deer (Cervus elaphus) using antler form (number of points), a secondary sexual trait which shows little senescence, despite the occurrence of reproductive senescence. In line with expectations for traits that senesce, genetic variance in antler form increased with age and selection weakened with age. Therefore, there was no indication that a stronger selection on individuals that survived to older ages was countering the dilution of selection due to fewer individuals being alive. Furthermore, the effect of selective disappearance masking a slight decline in antler form in the oldest years was small. Interestingly, although genetic variance and positive selection of antler form were found, there was no evidence of a response to selection, supporting a genetic decoupling of antler senescence and reproductive senescence. Finally, a positive genetic covariance in antler form among age classes provides a possible explanation for the lack of senescence. These findings suggest that the antler form is under a genetic constraint that prevents it from senescing, providing an interesting evolutionary explanation for negligible senescence in a secondary sexual trait, and consequently, the existence of asynchrony in senescence among traits within populations.

Predicting yolk testosterone allocation using ecological contexts and species-specific traits.

The prenatal transfer of testosterone (T) from mother to offspring is an important source of phenotypic plasticity. In birds, exposure to ecologically relevant stimuli, such as social competition or an attractive mate, can cause females to deposit more T into their egg yolks. Exposure to elevated yolk T can modify the expression of several fitness-related traits in offspring (e.g. growth, immune function, secondary sex traits and behaviour). Despite some of these changes being potentially adaptive, not all studies find that yolk T levels change in response to ecologically relevant stimuli. This heterogeneity is currently unexplained, limiting our ability to predict inter-generational responses to ecological change. Here, we performed a systematic literature search and found 119 observations across 39 wild species that measured inter-female variation in yolk T allocation in response to various stimuli. We used boosted regression trees, a form of machine learning, to examine whether species-specific traits or variation in study-level variables could explain variation in yolk T allocation (i.e. statistically significant vs. non-significant responses). We found that both species-specific traits and study-level variables are important predictors of significant changes in yolk T levels. Geographic range (latitude and longitude), evolutionary distinctiveness, longevity, egg mass relative to female mass, sociality, migration status and time to fledge were among the top 10 most influential predictors of the 48 examined. We also found that studies measuring or manipulating social stimuli (e.g. competition and breeding density) or breeding date were more likely to detect changes in yolk T allocation compared with studies examining other ecological contexts. Overall, these data provide several testable hypotheses concerning yolk T allocation and its adaptive value across species and contexts. Additionally, these findings can help us predict how ecological changes will affect hormonal responses in females that can shape future generations.

PSLBII-20 Estimation of genetic parameters for methane emissions and residual feed intake in Nellore cattle

Abstract The objective of this study was to obtain (co)variance components, heritability, and genetic correlation estimates for enteric methane emissions, residual feed intake, growth, carcass and reproductive indicator traits. Data from 43 feed efficiency trials conducted over a 13-yr period on a single purebred Nellore herd in Central Brazil, comprising 3,400 intact males and 2,167 females, were analyzed. Trial data along with diet NDF content were used to estimate the methane emission (g CH4/kg carcass gain) for each individual, using an equation developed by Medeiros et al., 2014: CH4 (g/d) = -0.1011 + 0.02062*DMI (kg/d) + 0.001648*NDF (% of DMI). Other data included pedigree information, body weight (BW), carcass traits, and reproductive indicator traits. Continuous traits were analyzed using a linear animal model, and threshold traits were analyzed using a threshold animal model. Two-trait analyses were performed using the restricted maximum likelihood to estimate the variance components, heritabilities and genetic and phenotypic correlations among traits. The estimated heritability of methane emissions was 0.136 ± 0.0314. The genetic correlations of methane emissions with growth and carcass traits were low and not different from zero: BW at 450 d (0.064 ± 0.140), scrotal circumference at 365 d (0.188 ± 0.155), longissimus muscle area (-0.090 ± 0.132), 12th-13th rib fat (-0.122 ± 0.142), rump fat (0.080 ± 0.119), intramuscular fat % (-0.108 ± 0.152), BW at 210 d (-0.077 ± 0.168). By contrast, there were the low genetic correlation of methane emissions with early calving probability (-0.260; -0.504 – 0.026); moderate genetic correlations of methane emissions with age at first calving (0.519 ± 0.202) and DM intake (0.512 ± 0.116); and the high correlation of methane with residual feed intake (RFI; 0.832 ± 0.073). Thus, selection to improve weaning and yearling weights, and carcass traits would not affect methane emissions. Genetic selection to reduce methane emissions is feasible and would also reduce DMI and RFI, as well as female sexual precocity traits. Conversely, selection to improve RFI can be used to identify animals with decreased methane emissions. Medeiros, S. R, L. G. Baioni, A. Berndt, M. C. Freua, T. Z. Albertini, C. Costa Jr., e G. B. Feltrin (2014) Modeling enteric methane emission from beef cattle in Brazil: A proposed equation performed by principal component analyses and mixed modeling multiple regression. Proceedings, Livestock, Climate Change and Food Security Conference, Madrid.

Evolutionary changes of noncoding elements associated with transition of sexual mode in Caenorhabditis nematodes.

The transition of the sexual mode occurs widely in animal evolution. In Caenorhabditis nematodes, androdioecy, a sexual polymorphism composed of males and hermaphrodites having the ability to self-fertilize, has evolved independently multiple times. While the modification of noncoding regulatory elements likely contributed to the evolution of hermaphroditism, little is known about these changes. Here, we conducted a genome-wide analysis of conserved noncoding elements (CNEs) focusing on the evolution of hermaphroditism in Caenorhabditis nematodes. We found that, in androdioecious nematodes, mutations rapidly accumulated in CNEs' neighboring genes associated with sexual traits. Expression analysis indicate that the identified CNEs are involved in spermatogenesis in hermaphrodites and associated with the transition of gene expression from dioecious to androdioecious nematodes. Last, genome editing of a CNE neighboring laf-1 resulted in a change in its expression in the gonadal region undergoing spermatogenesis. Our bioinformatic and experimental analyses highlight the importance of CNEs in gene regulation associated with the development of hermaphrodites.

Sexual dimorphism and functional allometry in scorpions: A comparative study from a neotropical species

Sexual dimorphism (SD), the divergence of secondary sexual traits between males and females within a species, can arise from diverse evolutionary forces, such as natural selection, mate choice, and intrasexual competition. Allometric scaling patterns of dimorphic traits are related to their functional roles and the different selective pressures that affect each sex. Generally, traits that threaten rivals involved in intrasexual competition tend to exhibit the highest allometric slopes. Conversely, non-sexual traits often display isometric scaling, while genitalia and traits in direct contact between the sexes during courtship and copulation typically show hypoallometry. A good approach to study patterns of SD and allometry is to complement interspecific studies with analyzes of case studies, where the functional aspect is known in detail. Here, we review the occurrence of SD and evaluation of allometry in the Order Scorpiones, allowing us to compare general trends in a broader comparative framework within the group. In addition, we examined SD and allometric slopes of multiple traits (including somatic traits used in sexual and non-sexual interactions, as well as genitalia) in adult individuals of the scorpion Timogenes elegans (Scorpiones, Bothriuridae). We found that at an interspecific level there was a variation in SD between species and morphological traits, with most traits showing a male-biased SD, except for the chelicerae, which were found to be wider in females. Regarding SD studies, we found relatively few reports of functional allometry showing differences in allometric patterns between species. The results in T. elegans follow some of the general patterns found in other scorpions. We found hypoallometry in genital traits and hyperallometry in the pedipalps of both sexes, with steeper allometric slopes observed for pedipalp height in males. These results suggest that genital traits are under stabilizing selective pressure, while pedipalps in both sexes may be under natural and sexual selective pressure. Understanding allometric patterns and their relationship to function in scorpions provides significant insights into the evolutionary pressures driving the divergence of morphological traits used in both sexual and non-sexual contexts.

Genital Modifications in Prepubescent Minors: When May Clinicians Ethically Proceed?

When is it ethically permissible for clinicians to surgically intervene into the genitals of a legal minor? We distinguish between voluntary and nonvoluntary procedures and focus on nonvoluntary procedures, specifically in prepubescent minors (“children”). We do not address procedures in adolescence or adulthood. With respect to children categorized as female at birth who have no apparent differences of sex development (i.e., non-intersex or “endosex” females) there is a near-universal ethical consensus in the Global North. This consensus holds that clinicians may not perform any nonvoluntary genital cutting or surgery, from “cosmetic” labiaplasty to medicalized ritual “pricking” of the vulva, insofar as the procedure is not strictly necessary to protect the child’s physical health. All other motivations, including possible psychosocial, cultural, subjective-aesthetic, or prophylactic benefits as judged by doctors or parents, are seen as categorically inappropriate grounds for a clinician to proceed with a nonvoluntary genital procedure in this population. We argue that the main ethical reasons capable of supporting this consensus turn not on empirically contestable benefit–risk calculations, but on a fundamental concern to respect the child’s privacy, bodily integrity, developing sexual boundaries, and (future) genital autonomy. We show that these ethical reasons are sound. However, as we argue, they do not only apply to endosex female children, but rather to all children regardless of sex characteristics, including those with intersex traits and endosex males. We conclude, therefore, that as a matter of justice, inclusivity, and gender equality in medical-ethical policy (we do not take a position as to criminal law), clinicians should not be permitted to perform any nonvoluntary genital cutting or surgery in prepubescent minors, irrespective of the latter’s sex traits or gender assignment, unless urgently necessary to protect their physical health. By contrast, we suggest that voluntary surgeries in older individuals might, under certain conditions, permissibly be performed for a wider range of reasons, including reasons of self-identity or psychosocial well-being, in keeping with the circumstances, values, and explicit needs and preferences of the persons so concerned. Note: Because our position is tied to clinicians’ widely accepted role-specific duties as medical practitioners within regulated healthcare systems, we do not consider genital procedures performed outside of a healthcare context (e.g., for religious reasons) or by persons other than licensed healthcare providers working in their professional capacity.

Pollinator response to yellow UV-patterned versus white UV-patternless flower dimorphism in Anemone palmata.

Flower colour polymorphisms are uncommon but widespread among angiosperms and can be maintained by a variety of balancing selection mechanisms. Anemone palmata is mostly yellow-flowered, but white-flowered plants coexist in some populations. We analysed the distribution of colour morphs of A. palmata across its range. We also characterised their colours and compared their vegetative and sexual reproductive traits, pollinator attention and fitness. The range of A. palmata is limited to the Western Mediterranean, while white-flowered plants are restricted to Portugal and SW Spain, where they occur at low proportions. Yellow flowers have a characteristic UV pattern, with a UV-absorbing centre and UV-reflecting periphery, which is absent in the white morph. Colour features of both morphs were highly delineated, making it easy for pollinators to distinguish them. Both morphs were protogynous, with the same duration of sexual stages, and the main floral traits related to pollinator attraction, apart from flower colour, were similar. Hymenoptera and Diptera were the main pollinators, showing preference for the yellow morph, clear partitioning of pollinator groups between the two colour morphs and a marked constancy to flower colour during foraging. Both morphs combined clonal propagation with sexual reproduction, but sexual reproductive potential was lower in white-flowered plants. Finally, female fitness was higher in the yellow morph. Pollinator partitioning and colour constancy could maintain this polymorphism, despite the lower visitation rate and fitness of white-flowered plants, which could facilitate their clonal propagation.

Fruit resources shape sexual selection processes in a lek mating system.

The degree to which within-population variation in sexual trait expression relates to resource heterogeneity remains poorly explored. This is particularly true in lek-mating species, where genetic explanations for male phenotypic variance and mating success are dominant. Here, we demonstrate a link between fine-scale fruit resource availability and indices of male mating success in the white-bearded manakin (Manacus manacus), a lek-mating frugivorous bird that produces energetically costly courtship displays. We used motion-activated camera traps to monitor male display behaviour and female visitation at male courts while concurrently conducting twice-monthly fruit surveys around courts. We observed significant variability in ripe fruit biomass among display courts and leks, and mean fruit biomass at courts significantly predicted male display rates. In turn, male display rate was the strongest predictor of female visitation to courts. Causal modelling supported the hypothesis that hyper-local fruit availability indirectly affects female visitation via its direct effects on male display rate. The demonstration that resource availability at fine spatial scales predicts display rate in a lekking organism-for which resource-related variables are typically not considered to play important roles in shaping male reproductive variance-has implications for the expression, honesty and maintenance of sexually selected traits under fluctuating ecological conditions.

Daily variation and repeatability of advertisement calls in an austral temperate forest frog under controlled conditions

AbstractEstimating repeatability allows a first approximation that may indicate a potential response to selection of sexual traits. Acoustic sexual signals comprise spectral and temporal variables, where the former generally have lower intra‐individual variation and higher repeatability values. Studies of repeatability in anurans have been conducted mainly in natural conditions, but the stability of laboratory settings allows extended recording intervals, favoring measurement accuracy. We conducted a study of variation and repeatability of the calls of males of Batrachyla taeniata, a frog from the South American temperate forest to evaluate under homogeneous environmental and social conditions: (i) the extent of variation in acoustic properties of calls within and among days, (ii) the extent of temporal variation in the repeatability of call properties, and (iii) differences in repeatability among call variables. Variation of acoustic properties differed within and across days of recording, call rate generally increased within and throughout days, suggesting sensitization processes. Call duration decreased during these time spans, yielding constant calling effort. In contrast, the dominant frequency decreased within days but increased across days. Overall repeatability differs significantly among variables: dominant frequency, call rate, and call duration having the highest, intermediate, and lowest values, respectively. The high repeatability of call rate relative to call duration contrasts with an opposing general tendency in previous studies in anurans. The repeatability of the three variables analyzed increases within days, and the repeatability of call rate also increases throughout days, highlighting the relevance of this variable for individual identity over different time ranges.

Testing the genomic overlap between intraspecific mating traits and interspecific mating barriers

Abstract Differences in interspecific mating traits, such as male sexual signals and female preferences, often evolve quickly as initial barriers to gene flow between nascent lineages, and they may also strengthen such barriers during secondary contact via reinforcement. However, it is an open question whether loci contributing to intraspecific variation in sexual traits are co-opted during the formation and strengthening of mating barriers between species. To test this, we used a population genomics approach in natural populations of Australian cricket sister species that overlap in a contact zone: Teleogryllus oceanicus and Teleogryllus commodus. First, we identified loci associated with intraspecific variation in T. oceanicus mating signals: advertisement song and cuticular hydrocarbon (CHC) pheromones. We then separately identified candidate interspecific barrier loci between the species. Genes showing elevated allelic divergence between species were enriched for neurological functions, indicating potential behavioral rewiring. Only two CHC-associated genes overlapped with these interspecific candidate barrier loci, and intraspecific CHC loci showed signatures of being under strong selective constraints between species. In contrast, 10 intraspecific song-associated genes showed high genetic differentiation between T. commodus and T. oceanicus, and 2 had signals of high genomic divergence. The overall lack of shared loci in intra vs. interspecific comparisons of mating trait and candidate barrier loci is consistent with limited co-option of the genetic architecture of interspecific mating signals during the establishment and maintenance of reproductive isolation.

Courtship performance, not ornamentation, predicts mating success in two sister-species of wolf spider with divergent phenotypes

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.

Cellular sex throughout the organism underlies somatic sexual differentiation

Sex chromosomes underlie the development of male or female sex organs across species. While systemic signals derived from sex organs prominently contribute to sex-linked differences, it is unclear whether the intrinsic presence of sex chromosomes in somatic tissues has a specific function. Here, we use genetic tools to show that cellular sex is crucial for sexual differentiation throughout the body in Drosophila melanogaster. We reveal that every somatic cell converts the intrinsic presence of sex chromosomes into the active production of a sex determinant, a female specific serine- and arginine-rich (SR) splicing factor. This discovery dismisses the mosaic model which posits that only a subset of cells has the potential to sexually differentiate. Using cell-specific sex reversals, we show that this prevalence of cellular sex drives sex differences in organ size and body weight and is essential for fecundity. These findings demonstrate that cellular sex drives differentiation programs at an organismal scale and highlight the importance of cellular sex pathways in sex trait evolution.

Natural variation in sexual traits and gene expression between selfing and outcrossing Arabidopsis lyrata suggests sexual selection at work.

Flowering plants show significant diversity in sexual strategies, profoundly impacting the evolution of sexual traits and associated genes. Sexual selection is one of the primary evolutionary forces driving sexual trait variation, particularly evident during pollen-pistil interactions, where pollen grains compete for fertilization and females select mating partners. Multiple mating may intensify competition among pollen donors for siring, while in contrast, self-fertilization reduces sire-sire competition, relaxing the sexual selection pressure. Traits involved in male-male competition and female choice are well described, and molecular mechanisms underlying pollen development and pollen-pistil interactions have been extensively studied in the model species Arabidopsis thaliana. However, whether these molecular mechanisms are involved in sexual selection in nature remains unclear. To address this gap, we measured intrinsic pollen performance and its interaction with female choice, and investigated the associated gene expression patterns in a selfing and an outcrossing population of Arabidopsis lyrata. We found that pollen germination and pollen tube growth were significantly higher in outcrossers than selfers, and this difference was accompanied by changes in expression of genes involved in vesicle transport and cytoskeleton. Outcrosser mother plants showed a negative impact on pollen tube growth compared to selfer mother plants, together with a difference of expression for genes involved in auxin and stress response, suggesting a potential mechanism for female choice through molecular crosstalk at the post-pollination stage. Our study provides insight on the impact of sexual selection on the evolution of sexual gene expression in plants.

Effects of the maternal social environment on the mating signals and mate preferences of adult offspring in Enchenopa treehoppers.

Much is known about how the maternal environment can shape offspring traits via intergenerational effects. It is less clear, however, whether such effects may reach adult offspring sexual traits, with potential consequences for sexual selection and speciation. Here, we report effects of adult female aggregation density on the mating signals and mate preferences of their offspring in an insect that communicates via plant-borne vibrational signals. We experimentally manipulated the density of aggregations experienced by egg-laying mothers, reared the offspring in standard densities, and tested for corresponding differences in their signals and preferences. We detected a strong effect in male signals, with sons of mothers that experienced low aggregation density signalling more. We also detected a weak effect on female mate preferences, with daughters of mothers that experienced low aggregation density being less selective. These adjustments may help males and females find mates and secure matings in low densities, if the conditions they encounter correspond to those their mothers experienced. Our results thus extend theory regarding adjustments to the social environment to the scale of intergenerational effects, with maternal social environments influencing the expression of the sexual traits of adult offspring.