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85 results for “testes size”
Data from: Context-dependence of maternal effects: testing assumptions of optimal egg size, differential- and sex-allocation models
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Testing the drivers of the temperature-size covariance using artificial selection
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Extensive geographic variation in testes size and ejaculate traits in a terrestrial-breeding frog
<p>Ejaculate traits vary extensively among individuals and species, but little is known about their variation among populations of the same species. Here, we investigated patterns of intraspecific variation in male reproductive investment in the terrestrial-breeding frog <i>Pseudophryne guentheri</i>. Like most anurans, breeding activity in <i>P. guentheri</i> is cued by precipitation, and therefore the timing and duration of breeding seasons differ among geographically separated populations, potentially leading to differences in the level of sperm competition. We therefore anticipated local adaptation in sperm traits that reflect these phenological differences among populations. Our analysis of six natural populations (two near the northern range edge and four central populations) revealed significant divergence in testes and ejaculate traits that correspond with latitude; males from the northern and dry edge of the species range had significantly smaller testes <span>containing fewer, smaller and less motile sperm compared to those from the more mesic central populations. These findings may reflect spatial variation in the strength of postcopulatory sexual selection among populations, likely driven by</span><span> local patterns of precipitation.</span></p>
Data from: Testing mechanisms of Bergmann's rule: phenotypic but no genetic change in body size in three passerine bird populations
Bergmann's rule predicts a decrease in body size with increasing temperature and has much empirical support. Surprisingly, we know very little about whether 'Bergmann size clines' are due to a genetic response or is a consequence of phenotypic plasticity. Here we use data on body size (mass and tarsus length) from three long-term (1979-2008) study populations of great tits (Parus major), in which there has been a temperature increase, to examine mechanisms behind Bergmann's rule. We show that adult body mass decreased over the study period in all populations and that tarsus length increased in one population. Both body mass and tarsus length were heritable and under weak positive directional selection, predicting an increase, rather than decrease, in body mass. There was no support for micro-evolutionary change and thus the observed declines in body mass were a result of phenotypic plasticity. Interestingly, this plasticity was not in direct response to temperature changes but seemed to be due to changes in prey dynamics. Our results caution against interpreting recent phenotypic body size declines as an adaptive evolutionary response to temperature changes and highlight the importance of considering alternative environmental factors when testing size clines.
Data from: Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis
Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomic measure of aerobic power of an animal. Although several authors have already compared heart masses across bird species, a phylogenetic comparative analysis of these comparisons is still lacking. Compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g., model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart sizes are consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e., hummingbirds) have substantially larger hearts than do other groups, that species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study shows that at a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level.
Testing size-frequency distributions as a method of ontogenetic aging: a life history assessment of hadrosaurid dinosaurs from the Dinosaur Park Formation of Alberta, Canada, with implications for hadrosaurid paleoecology
<p class="MsoNoSpacing">Hadrosaurid dinosaurs, the dominant large-bodied terrestrial herbivores in most Laurasian Late Cretaceous ecosystems, have an exceptional fossil record consisting of many species known from partial ontogenetic series making them an ideal clade with which to conduct life history studies. Previous research considered the Dinosaur Park Formation (DPF) of Alberta as an attritional, or time-averaged, sample and interpreted size-frequency distribution of long bones collected from the DPF with three size classes to suggest that hadrosaurids from the DPF attained near-asymptotic body size in under three years. This conflicted with previously published osteohistological estimates of 6+ years for penecontemporaneous hadrosaurids from the Two Medicine Formation (TMF) of Montana suggesting either extreme variation in hadrosaurid growth rates or that size-frequency distributions and/or osteohistology and growth modeling inaccurately estimate ontogenetic age.</p> <p>We tested the validity of the previously proposed size-age relationship of hadrosaurids from the DPF by significantly increasing sample size and combining data from size-frequency distributions and osteohistology across multiple long bones elements. The newly constructed size-frequency distributions typically reveal four relatively distinct size-frequency peaks that, when integrated with the osteohistological data, aligned with growth marks. The yearling size class was heavily underrepresented in the size-frequency distribution. If not due to preservation, this suggests that either juvenile (< 2 years of age) hadrosaurids from the DPF had increased survivorship following an initially high nestling mortality rate, or that yearlings were segregated from adults. A growth curve analysis revealed asymptotic body size was attained in approximately 7 years, which is consistent with hadrosaurids from the TMF. The data suggest size-frequency distributions of attritional samples underestimate age and overestimate growth rates, but when paired with osteohistology can provide unique life history insights.</p>
Data from: Synergism and antagonism of proximate mechanisms enable and constrain the response to simultaneous selection on body size and development time: an empirical test using experimental evolution
Natural selection acts on multiple traits simultaneously. How mechanisms underlying such traits enable or constrain their response to simultaneous selection is poorly understood. We show how antagonism and synergism among three traits at the developmental level enable or constrain evolutionary change in response to simultaneous selection on two focal traits at the phenotypic level. After 10 generations of 25% simultaneous directional selection on all four combinations of body size and development time in Manduca sexta (Sphingidae), the changes in the three developmental traits predict 93% of the response of development time and 100% of the response of body size. When the two focal traits were under synergistic selection, the response to simultaneous selection was enabled by juvenile hormone and ecdysteroids and constrained by growth rate. When the two focal traits were under antagonistic selection, the response to selection was due primarily to change in growth rate and constrained by the two hormonal traits. The approach used here reduces the complexity of the developmental and endocrine mechanisms to three proxy traits. This generates explicit predictions for the evolutionary response to selection that are based on biologically informed mechanisms. This approach has broad applicability to a diverse range of taxa, including algae, plants, amphibians, mammals, and insects.
Data from: Testing for Depéret's rule (body size increase) in mammals using combined extinct and extant data
Whether or not evolutionary lineages in general show a tendency to increase in body size has often been discussed. This tendency has been dubbed "Cope's rule" but because Cope never hypothesized it, we suggest renaming it after Depéret, who formulated it clearly in 1907. Depéret's rule has traditionally been studied using fossil data, but more recently a number of studies have used present-day species. While several paleontological studies of Cenozoic placental mammals have found support for increasing body size, most studies of extant placentals have failed to detect such a trend. Here, we present a method to combine information from present-day species with fossil data in a Bayesian phylogenetic framework. We apply the method to body mass estimates of a large number of extant and extinct mammal species, and find strong support for Depéret's rule. The tendency for size increase appears to be driven not by evolution toward larger size in established species, but by processes related to the emergence of new species. Our analysis shows that complementary data from extant and extinct species can greatly improve inference of macroevolutionary processes.
A Semi-Factorial Cluster-Randomized Trial to Estimate the Effect Size of Community Mobilization and VCT Vans on the Adoption of Voluntary Counseling and Testing (VCT) Services in Andhra Pradesh, India
ClinicalTrials.gov study NCT01160575. IPD Sharing: Not stated. Countries: 0. Publications: 3.
Testing size-frequency distributions as a method of ontogenetic aging: a life history assessment of hadrosaurid dinosaurs from the Dinosaur Park Formation of Alberta, Canada, with implications for hadrosaurid paleoecology
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Data from: Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis
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Data from: Testing for Depéret’s rule (body size increase) in mammals using combined extinct and extant data
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Extensive geographic variation in testes size and ejaculate traits in a terrestrial-breeding frog
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Data from: Testing mechanisms of Bergmann's rule: phenotypic but no genetic change in body size in three passerine bird populations
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Data from: Comparative tests of the role of dewlap size in Anolis lizard speciation
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Data from: Brain size affects performance in a reversal-learning test
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Data from: Testes size increases with sperm competition risk and intensity in bony fish and sharks
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Data from: Lineage diversity and size disparity in Musteloidea: testing patterns of adaptive radiation using molecular and fossil-based methods
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Data from: Synergism and antagonism of proximate mechanisms enable and constrain the response to simultaneous selection on body size and development time: an empirical test using experimental evolution
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Data from: Sexual ornaments but not weapons trade off against testes size in primates
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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.
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.