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1,369 results for “sexual dimorphism”
Data for: Sex matters: Predator presence induces sexual dimorphism in a monomorphic prey, from stress genes to morphological defenses
<p>Inducible defences allow prey to increase survival chances when predators are present while avoiding unnecessary costs in their absence. Many studies report considerable inter-individual variation in inducible-defence expression, yet what underlies this variation is poorly understood. A classic vertebrate example of a predator‐induced morphological defence is the increased body depth in crucian carp (<em>Carassius carassius</em>), which reduces the risk of predation from gape‐size limited predators. Here, we report that among-individual variation in morphological defence expression can be linked to sex. We documented sexual dimorphism in lakes in which crucian carp coexisted with predators, where females showed shallower relative body depths than males, but not in a predator-free lake. When exposing crucian carp from a population without predators to perceived predation risk in a laboratory environment (presence/absence of pike, <em>Esox lucius</em>), we found that males expressed significantly greater morphological defence than females, causing sexual dimorphism only in the presence of predators. We uncovered a correlative link between the sex-specific <em>inducible phenotypic </em>response and gene expression patterns in major stress-related genes (<em>POMC</em>,<em> MC3R</em>,<em> MC4R</em>). Together, our results highlight that sex-specific responses may be an important, yet underappreciated, component underlying inter-individual differences in the expression of inducible defences, even in species without pronounced sexual dimorphism. </p>
Condition dependence and sexual dimorphism in Drosophila prolongata
<p>Directional sexual selection drives the evolution of traits that are most closely linked to reproductive success, giving rise to trait exaggeration and sexual dimorphism. Exaggerated structures are often costly and, therefore, thought to be expressed in a condition-dependent manner. Sexual selection theory thus predicts a direct link between directional sexual selection, sexual dimorphism, and sex-specific condition dependence. However, only a handful of studies investigate the relationship between sexual dimorphism and condition dependence. Using 21 genetic lines of <em>Drosophila prolongata</em>, we here compared the degree of sexual dimorphism and sex-specific condition dependence, measured as allometric slopes, in sexually selected and non-sexual traits. Our data revealed male-biased sexual dimorphism in all traits examined, most prominently in the sexually selected forelegs. However, there was no relationship between the degree of sex-specific condition dependence and sexual dimorphism across traits and genetic lines. Our results contradict theoretical predictions and highlight the importance of understanding the role of exaggerated traits in the context of both sexual and natural selection.</p>
Sexually antagonistic selection maintains genetic variance when sexual dimorphism evolves
<p>Breeding design data for body size in seed beetles (a sexually antagonistic trait) after 10 generations under different artificial selection conditions to test the effects of selection on the genetic variance of body size. The breeding design and sample size of the study allow us to partition genetic variances into additive autosomal, additive sex-linked, autosomal dominance and X-linked dominance variance.<br><br>See related dataset for body size data of the ancestral population before selection.</p>
Influence of microhabitat, fecundity, and parental care on the evolution of sexual size dimorphism in Caribbean Eleutherodactylus frogs
<p><span>Rensch's rule suggests that sexual size dimorphism (SSD) increases with species size when males are the larger sex, whereas it decreases when females are the larger sex. However, the process responsible for this pattern remains obscure. SSD can result from sexual selection, such as intra-sexual competition for access to mates, or from natural selection, due to resource partitioning or fecundity selection. We studied SSD in Caribbean <em>Eleutherodactylus</em> frogs using phylogenetic comparative methods to investigate the influence of microhabitat, fecundity, and parental care. Our results show that in Caribbean <em>Eleutherodactylus,</em> females tend to be larger and, contrary to Rensch's rule, dimorphism increases with species size. SSD was not related to microhabitat use. However, SSD was positively correlated with fecundity, mediated by a greater increase in female size. SSD was also influenced by parental care, suggesting that male care promotes larger male size and reduces the female bias in SSD. As suggested for other anurans, female-biased SSD in Caribbean <em>Eleutherodactylus</em> results from fecundity selection, although the magnitude is countered by increased male size in species with paternal care. Our results highlight the importance of considering various selective forces that may act in concert to influence the evolution of sexual size dimorphism.</span></p>
Genetic variation in sexual size dimorphism is associated with variation in sex-specific plasticity in Drosophila
<p><span>The difference in body size between females and males, or sexual size dimorphism (SSD), is ubiquitous, and yet we have a poor understanding of the developmental-genetic mechanisms that generate it, and how these mechanisms may vary within and among species. Such an understanding of the genetic architecture of SSD is important if we are to evaluate alternative models of SSD evolution, but is difficult to describe because SSD is a characteristic of populations, not individuals. Here, we overcome this challenge by using isogenic lineages of <em>Drosophila</em> to measure SSD for 196 genotypes. We demonstrate extensive genetic variation for SSD, primarily driven by higher levels of genetic variation for body size among females than males. While we observe a general increase in SSD with sex-averaged body size (pooling for sex) among lineages, the vast majority of variation in SSD is independent of sex-averaged body size, and shows a strong genetic correlation with sex-specific plasticity, such that increased female-biased SSD is associated with increased body-size plasticity in females. Our data are consistent with the condition-dependence hypothesis of sexual dimorphism, and suggest that SSD in <em>Drosophila</em> is a consequence of selection on the developmental-genetic mechanisms that regulate the plasticity of body size. </span></p>
Ecology, sexual dimorphism, and jumping evolution in anurans
<p>Sexual dimorphism is a common feature of animals, and selection for sexually dimorphic traits may affect both functional morphological traits and organismal performance. Trait evolution through natural selection can also vary across environments. However, whether the evolution of organismal performance is distinct between the sexes is rarely tested in a phylogenetic comparative context. Anurans commonly exhibit sexual size dimorphism, which may affect jumping performance given the effects of body size on locomotion. They also live in a wide variety of microhabitats. Yet the relationships among dimorphism, performance, and ecology remain underexamined in anurans. Here, we explore relationships between microhabitat use, body size, and jumping performance in males and females to determine the drivers of dimorphic patterns in jumping performance. Using methods for predicting jumping performance through anatomical measurements, we describe how fecundity selection and natural selection associated with body size and microhabitat have likely shaped female jumping performance. We found that the magnitude of sexual size dimorphism (where females are about 14% larger than males) was much lower than dimorphism in muscle volume, where females had 42% more muscle than males (after accounting for body size). Despite these sometimes-large averages, phylogenetic t-tests failed to show statistical significance of sexual dimorphism for any variable, indicating sexually dimorphic species tend to be closely related. While sexual dimorphism of jumping performance did not vary among microhabitats, we found female jumping velocity and energy differed across microhabitats. Overall, our findings indicate that differences in sex-specific reproductive roles, size, jumping-related morphology, and performance are all important determinants in how selection has led to the incredible ecophenotypic diversity in anurans.</p>
Sexual dimorphism in specialist pollinated dioecious species with complex flowers
<div> Premise <p>Pollinators with flower constancy and long nectar-feeding organs should favour less or no sexual dimorphism in the individual flowers of dioecious plants. This hypothesis is deduced because such pollinators can discriminate between intersexual flower size differences, and morphological differences between male and female flowers often diminish pollen transfer.</p> Methods <p>We compared floral traits and pollinator behaviour between sexes in the hawkmoth-pollinated species, <em>Trichosanthes cucumeroides</em>. We focused on the roles of elaborate petal fringes in pollinator attraction and pollination success of female and male flowers by conducting field pollinator observations and fringe removal experiments.</p> Results <p>Female flowers had a similar front flower size and fringe extension as male flowers, supporting our hypothesis. In contrast, females allocated fewer resources to floral biomass. Additionally, they had smaller and narrower petal lobes, lower fringe density, shorter tubes with inferior nectar rewards, and lower display size than males, which is inconsistent with the hypothesis. Nocturnal hawkmoths prefer flowers with long fringe extensions. Fringe removal significantly decreased hawkmoth visitations to both female and male flowers but reduced success only in females. A literature survey indicated that specialist-pollinated species tend to exhibit similar or larger female attraction to floral organs more frequently than generalist-pollinated species.</p> Conclusions <p>Female flowers have evolved similar fringe extensions to male flowers, likely increasing pollinator attraction even slightly, and exhibited lower biomass of other floral parts and nectar production than male flowers. Our findings imply that female-biased resource limitation and flower-size-sensitive pollinators together exert sex-specific selection of floral traits in<em> T. cucumeroides</em>.</p> </div>
Data and code for: Sex-specific trait architecture in a sexually size dimorphic spider
<p class="MsoNormal">Sexual dimorphism, or sex-specific trait expression, may evolve when selection favours different optima for the same trait between sexes, i.e., under antagonistic selection. Intra-locus sexual conflict exists when the sexually dimorphic trait under antagonistic selection is based on genes shared between sexes. A common assumption is that the presence of sexual-size dimorphism (SSD) indicates that sexual conflict has been, at least partly, resolved via decoupling of the trait architecture between sexes. However, whether and how decoupling of the trait architecture between sexes has been realised often remains unknown. We tested for differences in architecture of adult body size between sexes in a species with extreme SSD, the African hermit spider (<em>Nephilingis cruentata</em>), where adult female body size greatly exceeds that of males. Specifically, we estimated the sex-specific importance of genetic and maternal effects on adult body size among individuals that we laboratory-reared for up to eight generations. Quantitative genetic model estimates indicated that size variation in females is to a larger extent explained by direct genetic effects than by maternal effects, but in males to a larger extent by maternal than by genetic effects. We conclude that this sex-specific body-size architecture enables body-size evolution to proceed much more independently than under a common architecture to both sexes.</p>
Data for: Size rather than complexity of sexual ornaments prolongs male metamorphosis and explains sexual size dimorphism in sepsid flies
<p><span>Male sexual ornaments often evolve rapidly and are thought to be costly, thus contributing to sexual size dimorphism. However, little is known about their developmental costs, and even less about costs associated with structural complexity. Here, we quantified the size and complexity of three morphologically elaborate sexually dimorphic male ornaments that starkly differ across sepsid fly species (Diptera: Sepsidae). Male forelegs range from being unmodified, like in most females, to being adorned with spines and large cuticular protrusions. The 4th abdominal sternites are either unmodified or are converted into complex de novo appendages. Male genital claspers range from small and simple to large and complex (e.g. bifurcated). </span><span>We tracked the development of 18 sepsid species from egg to adult to determine larval feeding and pupal metamorphosis times of both sexes. We then statistically explored whether pupal and adult body size, ornament size, and/or ornament complexity are correlated with sex-specific development times. Larval growth and foraging periods of male and female larvae did not differ, but the time spent in the pupal stage was ca. 5% longer for sepsid males despite emerging 9% smaller than females on average. Surprisingly, we found no evidence that sexual trait complexity prolongs pupal development beyond some effects of trait size. </span><span>Evolving more complex traits thus does not incur developmental costs.</span></p>
Oviposition behaviour is not affected by ultraviolet light in a butterfly with sexually-dimorphic expression of a UV-sensitive opsin
<p>Animal vision is important for mediating multiple complex behaviours. In <em>Heliconius</em> butterflies, vision guides fundamental behaviours such as oviposition, foraging and mate choice. Colour vision in <em>Heliconius</em> involves ultraviolet (UV), blue and long- wavelength sensitive photoreceptors (opsins). Additionally, <em>Heliconius</em> possess a duplicated UV opsin, and its expression varies widely within the genus. In <em>Heliconius</em> <em>erato</em>, opsin expression is sexually dimorphic; only females express both UV-sensitive opsins, enabling UV wavelength discrimination. However, the selective pressures responsible for sex-specific differences in opsin expression and visual perception remain unresolved. Female <em>Heliconius</em> invest heavily in finding suitable hostplants for oviposition, a behaviour heavily dependent on visual cues. Here, we tested the hypothesis that UV vision is important for oviposition in <em>H</em>. <em>erato</em> and <em>Heliconius</em> <em>himera</em> females by manipulating the availability of UV in behavioural experiments under natural conditions. Our results indicate that UV does not influence the number of oviposition attempts or eggs laid, and the hostplant, <em>Passiflora</em> <em>punctata</em>, does not reflect UV wavelengths. Models of <em>H. erato</em> female vision suggest only minimal stimulation of the UV opsins. Overall, these findings suggest that UV wavelengths do not directly affect the ability of <em>Heliconius</em> females to find suitable oviposition sites. Alternatively, UV discrimination could be used in the context of foraging or mate choice, but this remains to be tested.</p>
Sexual dimorphism in aipysurine sea snakes
<p class="MsoNormal">The transition from terrestrial to aquatic life by hydrophiine elapid snakes modified targets of natural selection and likely affected sexual selection also. Thus, the shift to marine life also might have affected sexual dimorphism. Our measurements of 419 preserved specimens of six species of aipysurine snakes (genera <em>Emydocephalus</em> and <em>Aipysurus</em>) revealed sexual dimorphism in mean adult snout-vent length (= SVL), body width relative to SVL, lengths and widths of heads and tails relative to SVL, and eye diameter relative to head length. Females averaged larger than males in all taxa, and generally were wider-bodied with shorter and wider tails and smaller eyes. For other traits, sexual dimorphism varied among species: for example, relative head length ranged from male-biased to female-biased, and head shape (width relative to length) was highly dimorphic only in <em>A. laevis</em>. The transition to marine life appears to have eliminated male-male combat (reducing selection for large males) and favoured visual rather than pheromone-based mate-searching (favouring larger eyes in males). Variation in head-size dimorphism may reflect intersexual niche partitioning, with different taxa following different trajectories. Repeated evolutionary transitions from terrestrial to aquatic life in snakes provide a powerful opportunity to explore selective forces on sexually dimorphic traits.</p>
Transcriptional patterns of sexual dimorphism and in host developmental programs in the model parasitic nematode Heligmosomoides bakeri
<p><strong>Background</strong></p> <p><em>Heligmosomoides bakeri </em>(often mistaken for <em>Heligmosomoides</em> <em>polygyrus</em>) is a promising model for parasitic nematodes with the key advantage of being amenable to study and manipulation within a controlled laboratory environment. While draft genome sequences are available for this worm, which allow for comparative genomic analyses between nematodes, there is a notable lack of information on its gene expression.</p> <p><strong>Methods </strong></p> <p>We generated biologically replicated RNA-seq datasets from samples taken throughout the parasitic life of <em>H. bakeri</em>. RNA from tissue-dwelling and lumen-dwelling worms, collected under a dissection microscope, was sequenced on an Illumina platform. <strong> </strong></p> <p><strong>Results</strong></p> <p>We find extensive transcriptional sexual dimorphism throughout the fourth larval and adult stages of this parasite and identify alternative splicing, glycosylation, and ubiquitination as particularly important processes for establishing and/or maintaining sex-specific gene expression in this species. We find sex-linked differences in transcription related to aging and oxidative and osmotic stress responses. We observe a starvation-like signature among transcripts whose expression is consistently upregulated in males, which may reflect a higher energy expenditure by male worms. We detect evidence of increased importance for anaerobic respiration among the adult worms, which coincides with the parasite's migration into the physiologically hypoxic environment of the intestinal lumen. Furthermore, we hypothesize that oxygen concentration may be an important driver of the worms encysting in the intestinal mucosa as larvae, which not only fully exposes the worms to their host's immune system but also shapes many of the interactions between the host and parasite. We find stage- and sex-specific variation in the expression of immunomodulatory genes and in anthelmintic targets. <strong> </strong></p> <p><strong>Conclusions</strong></p> <p>We examine how different the male and female worms are at the molecular level and describe major developmental events that occur in the worm, which extend our understanding of the interactions between this parasite and its host. In addition to generating new hypotheses for follow-up experiments into the worm's behavior, physiology, and metabolism, our datasets enable future more in-depth comparisons between nematodes to better define the utility of <em>H. bakeri</em> as a model for parasitic nematodes in general. </p>
Sex differences in the behavioural traits across ontogenetic stages in a sexually-size dimorphic spider
<p><span>Selection acts differently on females and males due to differences in potential reproductive rates, driving the evolution of sex differences in traits, including growth and behaviour. Additionally, selection pressures vary during an individual's ontogeny, with growth being crucial in early developmental stages and reproduction during adulthood, leading to age- and sex-specific behavioural strategies. In this study, we investigated a sexually-size dimorphic spider, the raft spider (<em>Dolomedes fimbriatus</em>), where females are substantially larger than males. We repeatedly observed spiders from juvenile to adult stages, examining boldness, voracity towards prey, and probability to attack. Our findings revealed that females exhibited greater boldness, voracity, and probability to back-attack the simulated attacker compared to males. Notably, the observed behaviours changed during ontogeny, with sex differences in the magnitudes and directions of change, indicating distinct life history strategies between sexes. Moreover, we detected positive associations between body mass or age and behavioural traits, supporting a proposed positive feedback loop between assets and behaviour. While mass and age were not significant confounding predictors in the analyses of sex differences in behaviour, some collinearity was present between sex, mass, and age, so that their effects on behavioural differences between sexes cannot be conclusively disentangled. Repeatability of behaviours was low but significant for boldness and probability to attack, with similar estimates between sexes. These results underscore the importance of considering sex-specific life history strategies in behavioural trait studies. </span></p>
Sexual dimorphism in the proventriculus of the buff-tailed bumblebee Bombus terrestris (L. 1758) (Hymenoptera: Apidae)
<p>This data set shows the measurements of the proventriculi from male and female <em>Bombus terrestris </em>individuals</p>
Reduced sexual size dimorphism in a pipefish population where males do not prefer larger females
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Data from: Larval development under continuous and dynamic light pollution alters sexual dimorphism in a moth species
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Juvenile hormone regulates the maturation of sexually dimorphic naïve ethanol olfactory preference in Drosophila melanogaster
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Data from: Functional trait plasticity diverges between sexes in African cichlids: a contribution toward ecological sexual dimorphism?
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Data from: Sexual dimorphism and retinal mosaic diversification following the evolution of a violet receptor in butterflies
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Using web-sourced photographs to examine temporal patterns in sex-specific diet of a highly sexually dimorphic raptor
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
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The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
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OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.