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1,369 results for “sexual dimorphism”
Data from: A functional trade-off between trophic adaptation and parental care predicts sexual dimorphism in cichlid fish
Although sexual dimorphism is widespread in nature, its evolutionary causes often remain elusive. Here we report a case where a sex-specific conflicting functional demand related to parental care but not to sexual selection explains sexual dimorphism in a primarily trophic structure, the gill rakers of cichlid fishes. More specifically, we examined gill raker length in a representative set of cichlid fish species from Lake Tanganyika featuring three different parental care strategies: (i) uni-parental mouthbrooding, whereby only one parental sex incubates the eggs in the buccal cavity; (ii) bi-parental mouthbrooding, whereby both parents participate in mouthbrooding; and (iii) nest guarding without any mouthbrooding involved. As predicted from these different parental care strategies, we find sexual dimorphism in gill raker length to be present only in uni-parental mouthbrooders, but neither in bi-parental mouthbrooders nor in nest guarders. Moreover, variation in the extent of sexual dimorphism among uni-parental mouthbrooders appears to be related to trophic ecology. Overall, we present a so far unrecognised scenario for the evolution of sexual dimorphism that is not related to sexual selection or initial niche divergence between sexes. Instead, sexual dimorphism in gill raker length in uni-parental mouthbrooding cichlid fish appears to be the consequence of a sex-specific functional trade-off between a trophic function present in both sexes, and a reproductive function present only in the brooding sex.
Data from: Effect of the MC1R gene on sexual dimorphism in melanin-based colorations
Variants of the melanocortin-1 receptor (MC1R) gene result in abrupt, naturally selected colour morphs. These genetic variants may differentially affect sexual dimorphism if one morph is naturally selected in the two sexes but another morph is naturally or sexually selected only in one of the two sexes (e.g. to confer camouflage in reproductive females or confer mating advantage in males). Therefore, the balance between natural and sexual selections can differ between MC1R variants, as suggest studies showing interspecific correlations between sexual dimorphism and the rate of nonsynonymous vs. synonymous amino acid substitutions at the MC1R. Surprisingly, how MC1R is related to within-species sexual dimorphism, and thereby to sex-specific selection, has not yet been investigated. We tackled this issue in the barn owl (Tyto alba), a species showing pronounced variation in the degree of reddish pheomelanin-based coloration and in the number and size of black feather spots. We found that a valine (V)-to-isoleucine (I) substitution at position 126 explains up to 30% of the variation in the three melanin-based colour traits and in feather melanin content. Interestingly, MC1R genotypes also differed in the degree of sexual colour dimorphism, with individuals homozygous for the II MC1R variant being 2 times redder and 2.5 times less sexually dimorphic than homozygous individuals for the VV MC1R variant. These findings support that MC1R interacts with the expression of sexual dimorphism and suggest that a gene with major phenotypic effects and weakly influenced by variation in body condition can participate in sex-specific selection processes.
Insights into the genetic architecture of sexual dimorphism from an interspecific cross between two diverging Silene (Caryophyllaceae) species
<p class="Cuerpo">The evolution of sexual dimorphism in species with separate sexes is influenced by the resolution of sexual conflicts creating sex differences through genetic linkage or sex-biased expression. Plants with different degrees of sexual dimorphism are thus ideal to study the genetic basis of sexual dimorphism. In this study we explore the genetic architecture of sexual dimorphism between <i>Silene latifolia </i>and<i> S. dioica. </i>These species have chromosomal sex determination and differ in the extent of sexual dimorphism. To test whether QTL for sexually dimorphic traits have accumulated on the sex chromosomes and to quantify their contribution to species differences, we create a linkage map and performed QTL analysis of life history, flower and vegetative traits using an unidirectional interspecific F2 hybrid cross. We found support for an accumulation of QTL on the sex chromosomes and that sex differences explained a large proportion of the variance between species, suggesting that both natural and sexual selection contributed to species divergence. Sexually dimorphic traits that also differed between species displayed transgressive segregation. We observed a reversal in sexual dimorphism in the F2 population, where males tended to be larger than females, indicating that sexual dimorphism is constrained within populations but not in recombinant hybrids. This study contributes to the understanding of the genetic basis of sexual dimorphism and its evolution in <i>Silene.</i></p>
Data from: Context-dependent expression of sexual dimorphism in island populations of the common wall lizard (Podarcis muralis)
The condition-dependent sexual dimorphism model explains the evolution and maintenance of sexual dimorphism in traits targeted by sexual selection, and predicts that the magnitude of sexual dimorphism depends on the variability of individual condition, male traits being more variable than female corresponding traits. Most convincing examples concern insects, while studies among vertebrates are scanty because manipulating condition often is not possible, and the time to reach sexual maturity may be too long. Islands offer a unique opportunity to compare how the environment affects the expression of sexual dimorphism, since they represent 'natural experimental sets' in which different populations of the same species may experience alternative environmental constraints. We investigated the occurrence of context-dependent expression in sexual dimorphism of head shape in insular populations of the common wall lizards (Podarcis muralis) inhabiting the Tuscan Archipelago (Tyrrhenian Sea). Alternative models were formulated: H0 assumes that the sexual dimorphism is uninfluenced by islands, H1 assumes the only effect of phylogeny, H2A and H2B account for the biogeography of the archipelago (island size and distance from the mainland), while H3 assumes island-specific effects on sexual dimorphism. Models were compared using Akaike's information criterion adjusted for multivariate analyses. All hypotheses performed better than H0, but H3 largely outperformed all other alternative hypotheses, indicating that environmental features of islands play an additive effect to ontogenetic, biogeographic and genetic factors in defining variation in head shape sexual dimorphism. Our results support the hypothesis of a context-dependent sexual dimorphism in common wall lizards
Data from: Sneaker males affect fighter male body size and sexual size dimorphism in salmon
Large male body size is typically favored by directional sexual selection through competition for mates. However, alternative male life-history phenotypes, such as "sneakers," should decrease the strength of sexual selection acting on body size of large "fighter" males. We tested this prediction with salmon species; in southern populations, where sneakers are common, fighter males should be smaller than in northern populations, where sneakers are rare, leading to geographical clines in sexual size dimorphism (SSD). Consistent with our prediction, fighter male body size and SSD (fighter male∶female size) increase with latitude in species with sneaker males (Atlantic salmon Salmo salar and masu salmon Oncorhynchus masou) but not in species without sneakers (chum salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha). This is the first evidence that sneaker males affect SSD across populations and species, and it suggests that alternative male mating strategies may shape the evolution of body size.
Data from: Thermoregulation as an alternate function of the sexually dimorphic fiddler crab claw
Fiddler crabs are highly sexually-dimorphic. Males possess one small (minor) feeding claw and one greatly enlarged (major) claw; females possess two small claws. The major claw is used to attract mates and for burrow defense but is costly for the male to possess. We tested the hypothesis that the major claw also functions as a thermoregulatory structure, a function that would allow males to spend a greater amount of time on the surface, foraging and attracting potential mates. Fiddler crabs, Uca panacea, were exposed to a source of radiant heat and body temperatures were monitored. Four groups of crabs were tested: intact males, males with the minor claw removed, males with the major claw removed, and females. Males without the major claw increased in body temperature more rapidly and reached higher temperatures than males with the major claw intact, but were similar to females. These results support the hypothesized thermoregulatory function of the major claw. The major claw may function as a heat sink, transferring heat away from the body and dissipating it into the air. Enhanced thermoregulatory ability provided by the major claw may partially ameliorate the energetic costs of possessing such a large claw.
Data from: The B-matrix harbours significant and sex-specific constraints on the evolution of multi-character sexual dimorphism
The extent to which sexual dimorphism can evolve within a population depends on an interaction between sexually divergent selection and constraints imposed by a genetic architecture that is shared between males and females. The degree of constraint within a population is normally inferred from the intersexual genetic correlation, rmf. However, such bivariate correlations ignore the potential constraining effect of genetic covariances between other sexually co-expressed traits. Using the fruit fly Drosophila serrata, a species that exhibits mutual mate preference for blends of homologous contact pheromones, we tested the impact of between-sex between-trait genetic covariances using an extended version of the genetic variance-covariance matrix, G, that includes Lande's (1980) between-sex covariance matrix, B. We find that including B greatly reduces the degree to which male and female traits are predicted to diverge in the face of divergent phenotypic selection. However, the degree to which B alters the response to selection differs between the sexes. The overall rate of male trait evolution is predicted to decline, but its direction remains relatively unchanged, whereas the opposite is found in females. We emphasise the importance of considering the B-matrix in microevolutionary studies of constraints on the evolution of sexual dimorphism.
Data from: Ecology and sexual selection: evolution of wing pigmentation in calopterygid damselflies in relation to latitude, sexual dimorphism and speciation
Our knowledge about how the environment influences sexual selection regimes and how ecology and sexual selection interact is still limited. We performed an integrative study of wing pigmentation in calopterygid damselflies, combining phylogenetic comparative analyses, field observations and experiments. We investigated the evolutionary consequences of wing pigmentation for sexual dimorphism, speciation and extinction and addressed the possible thermoregulatory benefits of pigmentation. First, we reconstructed ancestral states of male and female phenotypes and traced the evolutionary change of wing pigmentation. Clear wings are the ancestral state and that pigmentation dimorphism is derived, suggesting that sexual selection results in sexual dimorphism. We further demonstrate that pigmentation elevates speciation and extinction rates. We also document a significant biogeographic association with pigmented species primarily occupying northern temperate regions with cooler climates. Field observations and experiments on two temperate sympatric species suggest a link between pigmentation, thermoregulation and sexual selection, although body temperature is also affected by other phenotypic traits such as body mass, microhabitat selection and thermoregulatory behaviors. Taken together, our results suggest an important role for wing pigmentation in sexual selection in males and in speciation. Wing pigmentation might not increase ecological adaptation and species longevity, and its primary function is in sexual signalling and species recognition.
Data from: Parasitism and the expression of sexual dimorphism
Although a negative covariance between parasite load and sexually selected trait expression is a requirement of few sexual selection models, such a covariance may be a general result of life-history allocation trade-offs. If both allocation to sexually selected traits and to somatic maintenance (immunocompetence) are condition dependent, then in populations where individuals vary in condition, a positive covariance between trait expression and immunocompetence, and thus a negative covariance between trait and parasite load, is expected. We test the prediction that parasite load is generally related to the expression of sexual dimorphism across two breeding seasons in a wild salamander population and show that males have higher trematode parasite loads for their body size than females and that a key sexually selected trait covaries negatively with parasite load in males. We found evidence of a weaker negative relationship between the analogous female trait and parasite infection. These results underscore that parasite infection may covary with expression of sexually selected traits, both within and among species, regardless of the model of sexual selection, and also suggest that the evolution of condition dependence in males may affect the evolution of female trait expression.
FIGURE 5 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 5. Relative deformations grids show the variation in the mean shape of the second abdominal segment for (a) females and (b) males.
FIGURE 4 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 4. Scatter plot of first versus second principal component axes for the total variation of the second abdominal pleura shape for females and males in Neocaridina davidi.
FIGURE 1 in Sexual dimorphism in a freshwater atyid shrimp (Decapoda: Caridea) with direct development: a geometric morphometrics approach
FIGURE 1. Location of landmarks and semilandmarks on each anatomic structure in Neocaridina davidi. (a) carapace; (b) second abdominal pleura; left side, lateral view.
FIGURE 8 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 8. Propephonte duangitensis sp. n. A–B, D (ɗ, COP 1941); C (Ψ, COP 1940). A, P3, anterior; B, P4, posterior; C, P5, anterior; D, P5, anterior.
FIGURE 7 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 7. Propephonte duangitensis sp. n. (Ψ, COP 1940). A, P1, anterior; B, left P2 exp2 and exp3, anterior; C, right P2, anterior; D, left P2 enp, anterior; E, right P3, posterior; F, left P3 enp, posterior; G, left P4, anterior.
FIGURE 2 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 2. Apistophonte wasiniensis sp. n. A–B, E–I (Ψ, COP 4727); C–D, J (ɗ, COP 4728). A, antennule and rostrum, dorsal; B, mandible; C, antennule (armature of segments 3–5 omitted), dorsal; D, antennule (segments 3–5), ventral; E, maxilliped; F, antenna; G, maxillule; H, maxilla; I, P5, anterior; J, P5, anterior.
FIGURE 6 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 6. Propephonte duangitensis sp. n. A–B, E–I (Ψ, COP 1940); C–D (ɗ, COP1941). A, antennule, ventral; B, antenna; C, antennule (armature of segments 3–5 omitted), dorsal; D, antennule (segments 3–5), ventral; E, rostrum; F, mandible; G, maxillule; H, maxilla; I, maxilliped.
FIGURE 4 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 4. Apistophonte wasiniensis sp. n. A (Ψ, COP 4727), urosome (copulatory pore arrowed), ventral. B (ɗ, COP 4728), second to fourth urosomite, ventral. C (Ψ, COP 4727), anal somite and caudal rami, dorsal.
FIGURE 5 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 5. Propephonte duangitensis sp. n. (Ψ, COP 4726). A, habitus, dorsal; B, habitus, lateral. C (ɗ, COP 1942), habitus, dorsal.
FIGURE 3 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 3. Apistophonte wasiniensis sp. n. (Ψ, COP 4727). A, P1, anterior; B, P2, anterior; C, P3, anterior; D, P4, anterior. E (ɗ, COP 4728), P3, anterior.
FIGURE 1 in Two new genera of Laophontidae (Copepoda: Harpacticoida) without sexual dimorphism in the endopods of the swimming legs
FIGURE 1. Apistophonte wasiniensis sp. n. (Ψ, COP 4727). A, habitus, dorsal; B, habitus, lateral. C (ɗ, COP 4728), habitus, dorsal.
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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)
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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.
International Brain Laboratory public data
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.
OpenNeuro
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.