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1,369 results for “sexual dimorphism”
An effect size statistical framework for investigating sexual dimorphism in non-avian dinosaurs and other extinct taxa
<p>Despite reports of sexual dimorphism in extinct taxa, such claims in non-avian dinosaurs have been underrepresented recently (~the last decade) and often criticized. Since dimorphism is widespread in sexually reproducing organisms today, underrepresentation might suggest either methodological shortcomings or that this diverse group exhibited highly unusual reproductive biology. Univariate significance testing, especially for bimodality, is ineffective and prone to false negatives. Species recognition and mutual sexual selection hypotheses, therefore, may not be required to explain supposed absence of sexual dimorphism across the grade, likely a type II error. Instead, multiple lines of evidence support sexual selection and variation of structures consistent with secondary sexual characteristics, strongly suggesting sexual dimorphism in non-avian dinosaurs. We propose a framework for studying sexual dimorphism in fossils, focusing on likely secondarily sexual traits and testing against all alternate hypotheses for variation in them using multiple lines of evidence. We use effect size statistics appropriate for low sample sizes, rather than significance testing, to analyze potential divergence of growth curves in traits and constrain estimates for dimorphism magnitude. In many cases, estimates of sexual variation can be reasonably accurate, and further developments in methods to improve sex assignments and account for intrasexual variation (e.g., mixture modelling) will improve accuracy. It is better to compare estimates for the magnitude of and support for dimorphism between datasets than to dichotomously reject or fail to reject monomorphism in a single species, enabling the study of sexual selection across phylogenies and time. We defend our approach with simulated and empirical data, including dinosaur data, showing that even simple approaches can yield fairly accurate estimates of sexual variation in many cases, allowing for comparison of species with high and low support for sexual variation.</p>
Shifts in sexual dimorphism across a mass extinction in ostracods: implications for sexual selection as a factor in extinction risk
<p>Sexual selection often favors investment in expensive sexual traits that help individuals compete for mates. In a rapidly changing environment, however, allocation of resources to traits related to reproduction at the expense of those related to survival may elevate extinction risk. Empirical testing of this hypothesis in the fossil record, where extinction can be directly documented, is largely lacking. The rich fossil record of cytheroid ostracods offers a unique study system in this context: the male shell is systematically more elongate than that of females, and thus the sexes can be distinguished, even in fossils. Using mixture models to identify sex clusters from size and shape variables derived from the digitized valve outlines of adult ostracods, we estimated sexual dimorphism in ostracod species before and after the Cretaceous/Paleogene mass extinction in the United States Coastal Plain. Across this boundary, we document a substantial shift in sexual dimorphism, driven largely by a pronounced decline in the taxa with dimorphism indicating both very high and very low male investment. The shift away from high male investment, which arises largely from evolutionary changes within genera that persist through the extinction, parallels extinction selectivity previously documented during the Late Cretaceous under a background extinction regime. Our results suggest that sexual selection and the allocation of resources towards survival versus reproduction may be an important factor for species extinction during both background and mass extinctions. </p>
A study of tactical and sexual dimorphism in cognition with insights for sexual conflict
<p>The sexes may have different optima in cognitive traits due to differences in life history strategies and the expense of investing in metabolically costly brain tissue. However, given genetic correlations, each sex could be constrained from reaching its cognitive optimum due to intralocus sexual conflict. We compared learning performance of two male alternative reproductive tactics and females from known genotypes (both sire and dam) in the livebearing fish <i>Xiphophorus multilineatus</i>. We predicted that females' learning performance would align with the learning performance of their sire's genotype due to genetic correlation of cognitive traits. Using a classical conditioning assessment (associating a flashing light with a food reward), we detected mating tactic dimorphism in learning performance, with the behaviourally plastic sneaker males outperforming the behaviourally fixed <a>courter </a>males. Unexpectedly, females sired by the faster-learning sneaker males performed significantly worse than sneaker males. We also detected an influence of brain size on female learning performance. Previous studies have found that females invest more in offspring sired by courter males, and we therefore hypothesize that maternal effects could potentially mitigate the influence of sexual conflict on a cognitive trait.</p>
Foraging niche overlap during chick-rearing in the sexually dimorphic Westland petrel
Most Procellariform seabirds are pelagic, breed in summer when prey availability peaks, and migrate for winter. They also display a dual foraging strategy (short and long trips) and sex-specific foraging. The Westland petrel Procellaria westlandica, a New Zealand endemic, is one of the rare seabirds breeding in winter. Preliminary findings on this large and sexually-dimorphic petrel suggest a foraging with no evidence of a dual strategy, within a narrow range and with shared areas between sexes. To investigate further this unusual strategy, the present study determined the fine-scale at-sea behaviours (GPS and accelerometer data loggers) and trophic niches (stable isotopes in whole blood) of chick-rearing individuals (16 males, 13 females). All individuals foraged on the shelf slope of the west coast of New Zealand's South Island with short, unimodal trips. Both sexes foraged at similar intensity without temporal, spatial or isotopic niche segregation. These findings suggest the presence of a winter prey resource close to the colony, sufficient to satisfy the nutritional needs of breeding without intra-specific competition avoidance or increased foraging effort. Additional data are needed to assess the consistency of foraging niche between the sexes and its reproductive outcomes in view of anticipated environmental changes.
Images from: Sexual dimorphism in shells of Cochlostoma septemspirale (Caenogastropoda, Cyclophoroidea, Diplommatinidae, Cochlostomatinae)
<p>Here we provide the complete set of images used by <a href="https://doi.org/10.3897/zookeys.208.2869">Reichenbach et al. (2012)</a> as basis for a dataset of distance measurements. The images are available in two versions: The first has the measured distances marked in the photo; the second is the original, untouched file.</p> <p>Metadata for images may be retrieved via the image number, which is also part of the dataset published separately by <a href="https://doi.org/10.5281/zenodo.4267813">Reichenbach et al. (2020)</a>. There, the relevant information (sex of specimen, locality, date of collecting, etc.) is given for each specimen.</p> <p>Cited papers are listed below in the "References" section.</p>
DNA methylation regulates transcription factor specific neurodevelopmental but not sexually dimorphic gene expression dynamics in zebra finch telencephalon
<p>Supplementary Information for the manuscript: "DNA methylation regulates transcription factor specific neurodevelopmental but not sexually dimorphic gene expression dynamics in zebra finch telencephalon"</p>
FIGURES 26A–D in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 26A–D. Distribution maps. (A) Scraptogetus anthracinus, (B) Scraptogetus arboreus, (C) Transrenus thulater, sp. n. and Pseudozena denticulata, sp. n., and (D) Zenascus antennalis.
FIGURES 22A–E in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 22A–E. Abdominal ventrite illustrations for Zenascus species showing generalized punctation pattern. (A) Z. antennalis, male; (B) Z. xenarthrus, male; (C) Z. roberti, sp. n., male; (D) Z. luniger, male; (E) Z. incensum, sp. n., male.
FIGURES 21A–E in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 21A–E. Abdominal ventrite illustrations for Zenascus species showing generalized punctation pattern. (A) Z. coloratus (Broun), male; (B) Z. obscurus (Broun), male; (C) Z. aurum, sp. n., male; (D) Z. nitidus (Broun), male; (E) Z. elenae, sp. n., male.
FIGURES 17A–D in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 17A–D. Scanning electron microscope images, Zenascus species, metatibia (A) Z. nitidus, male; (B) Z. nitidus, female; (C) Z. elenae, sp. n., male; (D) Z. elenae, sp. n., female. Scale bars = 30μm.
FIGURES 13A–H in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 13A–H. Zenascus obscurus, scanning electron micrographs. (A) head, frontal view; (B) antenna; (C) pronotum (D) proleg; (E) metatibia; (F) metaventrite; (G) abdomen; (H) tergite VII.
FIGURES 10A–C in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 10A–C. Male genitalia illustrations. (A) Scraptogetus anthracinus; (B) Transrenus thulater, sp. n.; and (C) Pseudozena denticulata, sp. n.
FIGURES 20A–J in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 20A–J. Scanning electron microscope images, ventral view of metafemora for Zenascus species. (A) Z. coloratus, male; (B) Z. obscurus, male; (C) Z. aurum, sp. n., male; (D) Z. nitidus, female; (E) Z. elenae, sp. n., male; (F) Z. antennalis, female; (G) Z. xenarthrus, male; (H) Z. roberti, sp. n., male; (I) Z. luniger, male; (J) Z. incensum, sp. n., male. Scale bars = 60μm.
FIGURE 25 in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURE 25. One of two most parsimonious trees recovered from Maximum Parsimony (MP) phylogenetic analysis based on 19 morphological characters for the New Zealand species of Zenascus. (L = 39; CI = 0.61; RI = 0.72). Numbers above branches indicate Bremer (Decay index) support values.
FIGURES 16A–C in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 16A–C. Scanning electron microscope images, Zenascus species, protarsomeres displaying spine and sexual dimorphism present in some species. (A) Z. obscurus, male; (B) Z. obscurus, female (C) Z. roberti, sp. n., male. Scale bars = 20μm.
FIGURES 12A–E in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 12A–E. Dorsal habitus images. (A) Zenascus antennalis (Broun), male; (B) Zenascus xenarthrus (Broun), male; (C) Zenascus roberti sp. n., male; (D) Zenascus luniger (Champion), male; (E) Zenascus incensum sp. n., male. Scale bars = 1.0 mm.
FIGURES 11A–E in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 11A–E. Dorsal habitus images. (A) Zenascus coloratus (Broun), male; (B) Zenascus obscurus (Broun), male; (C) Zenascus aurum, sp. n., female; (D) Zenascus nitidus (Broun), male; (E) Zenascus elenae, sp. n., male. Scale bars = 1.0 mm.
FIGURES 15A–C in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 15A–C. Scanning electron microscope images of Zenascus species with close-ups of male antennomeres 7–9. (A) Z. roberti, sp. n.; (B) Z. luniger; (C) Z. incensum, sp. n.. Scale bars = 20μm.
FIGURES 18A–E in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 18A–E. Scanning electron microscope images, Zenascus species, elytron, dorsal view. (A) Z. coloratus; (B) Z. obscurus; (C) Z. aurum, sp. n.; (D) Z. nitidus; (E) Z. elenae, sp. n. Scale bars = 10μm.
FIGURES 14A–J in Sexual Dimorphism of New Zealand Puppet Beetles (Aderidae, Coleoptera, Tenebrionoidea): Systematic Revision, Description of Three New Genera, and Phylogeny for Zenascus, gen. n.
FIGURES 14A–J. Antennal illustrations for Zenascus species, male on left, female on right.(A) Z. coloratus; (B) Z. obscurus; (C) Z. aurum, sp. n.; (D) Z. nitidus; (E) Z. elenae, sp. n.; (F) Z. antennalis; (G) Z. xenarthrus; (H) Z. roberti, sp. n.; (I) Z. luniger; (J) Z. incensum, sp. n. Scale bar = 0.1 mm.
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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.