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1,245 results for “hypothesis”
Data from: Island-wide characterization of agricultural production challenges the demographic collapse hypothesis for Rapa Nui (Easter Island)
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Data and code for: Pneumococcus co-colonization and the stress-gradient-hypothesis
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Data for: A hypothesis for robust polarization vision: An example from the Australian Imperial Blue butterfly, Jalmenus evagoras
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Cracks in the mirror hypothesis: high specularity does not reduce detection or predation risk
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Data from: Mast fruiting in a large tropical African legume tree provides evidence for the nutrient resource limitation hypothesis
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Data from: No evidence for the melanin desiccation hypothesis in a larval Lepidopteran
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The adaptive significance of off-lek sociality in birds: A synthetic review, with evidence for the reproductive benefits hypothesis in Long-wattled umbrellabirds
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Data from: Testing the greater male variability hypothesis: male mountain chickadees exhibit larger variation in reversal learning compared to females
The 'greater male variability hypothesis' predicts that males exhibit larger ranges of variation in cognitive performance compared to females, however, support for this hypothesis has come exclusively from studies of humans. This scenario aligns with the fact that the vast majority of the literature assessing sex differences in cognition is based on studies of humans and a few other mammals. In order to elucidate the underpinnings of cognitive variation and the potential for fitness consequences, we must investigate sex differences in cognition in non-mammalian systems as well. Here we assess the performance of male and female food-caching birds on a spatial learning and memory task and a reversal spatial task to address whether there are sex differences in mean cognitive performance or in the range of variation in performance. For both tasks, male and female mean performance was similar across four years of testing; however, males did exhibit a wider range of variation in performance on the reversal spatial task compared to females. The implications for mate choice and sexual selection of cognitive abilities are discussed, with a call for further investigation into sex-related cognitive variation.
Data from: The island syndrome hypothesis is only partially validated in two rodent species in an inland-island system
<p><span>According to the island syndrome and island rule hypotheses, island isolation and reduced area lead to phenotypic shifts in ecologically relevant traits in insular populations compared to mainland ones. These hypotheses have been built up with oceanic islands in mind or islands where isolation is high and colonization rate relatively limited. This set of hypotheses, however, may not be applicable to other inland-island systems or recently fragmented landscapes. </span></p> <p><span>We investigated how island life leads to phenotypic changes in two rodent metapopulations: deer mice and red-backed voles in a fragmented system on a river in Canada. From 2013 to 2016, we sampled 454 deer mice and 665 red-backed voles spread across 10 islands and six mainland sites on river shores. We compared body mass, tail and hindfoot length, exploration, and reaction towards predators, between individuals from island and mainland sites, and assessed the role of connectivity, isolation and area of islands. </span></p> <p><span>Insular individuals from both species were less aggressive towards potential predators and insular mice were more thorough explorers compared to mainland ones. Male mice were heavier and juvenile mice had longer tails on islands. However, contrary to expectations, we found negative relationships between aggressiveness and juvenile exploration score with patch connectivity for mice. Island connectivity significantly affected tail length of mice through a concave relationship. Finally, vole aggressiveness and exploration of male mice were positively correlated to island isolation. </span></p> <p><span>Our study supports only partially the predictions of the island syndrome hypothesis. It provides empirical evidence that inland-island life can modify traits in deer mice, but less so in red-backed voles in a non-oceanic system. It also raises questions about the direct causal factors of these changes in a naturally fragmented landscape, and urges for more predictive models about phenotypic/genetic divergence among populations in natural and artificial fragmented landscapes.</span></p>
Data from: Exogenous testosterone increases the audience effect in healthy males: evidence for the social status hypothesis
<p>Several studies have implicated testosterone in the modulation of altruistic behaviours instrumental to advancing social status. Independent studies have also shown that people tend to behave more altruistically when being watched (i.e., audience effect). To date, little is known about whether testosterone could modulate the audience effect. In the current study, we tested the effect of testosterone on altruistic behaviour using a donation task, wherein participants were asked to either accept or reject a monetary transfer to a charity organization accompanying a personal cost either in the presence or absence of an observer. We administered testosterone gel or placebo to healthy young men (n = 140) in a double-blind, placebo-controlled, mixed design. Our results showed that participants were more likely to accept the monetary transfer to the charity when being observed compared to when they completed the task alone. More importantly, this audience effect was amplified among people receiving testosterone vs. placebo. Our findings suggest that testosterone administration increases the audience effect and further buttress the social status hypothesis, according to which testosterone promotes status-seeking behaviour in a context-dependent manner.</p>
Data from: A closer examination of the 'abundant center' hypothesis for reef fishes
<p>Aim: The 'abundant center' hypothesis states that species are more abundant at the center of their range. However, several recent large-scale studies have failed to find evidence for such a pattern. Here we use extensive global data of reef fishes to test the strength of the 'abundant center' pattern, and to examine variation in the patterns across species using life history and ecological traits.</p> <p>Location: Marine habitat at a global extent: from Indo-Pacific to Atlantic reefs.</p> <p>Methods: We used underwater visual estimates of fish abundance, containing 22,963 transects and 1,215 species. For each species we calculated the slope between abundance and distance to the range center, with the range center estimated using four different methods. We tested whether abundance patterns differ between the range core and margins using segmented regression. Meta-analytic methods were used to synthesize results across species, and to test whether species traits can explain variation in the fit to the pattern among species.</p> <p>Results: The method used to define the range center had a large effect on the results. Nevertheless, in all cases we found large variation between species. Results of the segmented regression revealed that changes in abundance across the range core are very small and that steep declines in abundance happen only toward the range margins. Body size and mean abundance were the main traits affecting the fit to the pattern across species.</p> <p>Main conclusions: We find large variation across species in the fit to the abundance center pattern. Nevertheless, we do find support for a general pattern of a range core with high, but variable, abundance and steep decline in abundance toward the range periphery. Thus, species do tend to be rare at the range margins, making then sensitive to extirpation due to both natural and anthropogenic impacts.</p>
Data from: Historical demography of four gecko species specializing in boulder cave habitat – its implications in the evolutionary dead end hypothesis and conservation
Specialization in narrow ecological niches might not only help species to survive in competitive or unique environments but also contribute to their extermination over evolutionary time. Although the "evolutionary dead end" hypothesis has long been debated, empirical evidence from species with detailed information on niche specialization and evolutionary history is still rare. Here we used a group of four closely related Cnemaspis gecko species that highly depend on granite boulder caves in the Mekong Delta to illuminate the potential impact of ecological specialization on their evolution and population dynamics. Isolated by the unsuitable habitat of a flood plain, these boulder-dwelling geckos are among the most narrowly distributed Squamata species in the world. We applied several coalescence-based approaches combined with the RAD-seq technique to estimate their divergence times, gene flow and demographic fluctuations during the speciation and population differentiation processes. Our results showed long-term population shrinkage in the four geckos and limited gene flow during their divergence. The results suggest that the erosion and fragmentation of the granite boulder hills have had great impacts on these populations' divergences and population declines. We argue that the specialist gecko's habitat specialization has facilitated the fine-scaled speciation in these granite rocky hills; in contrast, specialization might also have pushed these species toward the edge of extinction. Our study also emphasizes the conservation urgency of these vulnerable, cave-dependent geckos.
Data from: Life-history theory provides a framework for detecting resource limitation: a test of the Nutritional Buffer Hypothesis
<p>For ungulates and other long-lived species, life-history theory predicts that nutritional reserves are allocated to reproduction in a state-dependent manner because survival is highly conserved. Further, as per-capita food abundance and nutritional reserves decline (i.e., density-dependence intensifies), reproduction and recruitment become increasingly sensitive to weather. Thus, the degree to which weather influences vital rates should be associated with proximity to nutritional carrying capacity—a notion that we refer to as the Nutritional Buffer Hypothesis. We tested the Nutritional Buffer Hypothesis using six moose (<i>Alces alces</i>) populations that varied in calf recruitment (33-69 calves/ 100 cows). We predicted that populations with high calf recruitment were nutritionally buffered against the effects of unfavorable weather, and thus were below nutritional carrying capacity. We applied a suite of tools to quantify habitat and nutritional condition of each population and found that increased browse condition, forage quality, and body fat were associated with increased pregnancy and calf recruitment, thereby providing multiple lines of evidence that declines in calf recruitment were underpinned by resource limitation. From 2001 to 2015, recruitment was more sensitive to interannual variation in weather (e.g., winter severity, drought) and plant phenology (e.g., duration of spring) for populations with reduced browse condition, forage quality, and body fat, suggesting these populations lacked the nutritional reserves necessary to buffer demographic performance against the effects of unfavorable weather. Further, average within-population calf recruitment was determined by regional climatic variation, suggesting that the pattern of reduced recruitment near the southern range boundary of moose stems from an interaction between climate and resource limitation. When coupled with information on habitat, nutrition, weather, and climate, life-history theory provides a framework to estimate nutritional limitation, proximity to nutritional carrying capacity, and impacts of climate change for ungulates.</p>
Data and Code: No support for the genetic hypothesis of the Black-white achievement gap using polygenic scores and tests for divergent selection
<p>Data and Code for article "No support for the genetic hypothesis of the Black-white achievement gap using polygenic scores and tests for divergent selection"</p>
Figure 1. Phylogenetic relationships among eulophids inferred from 879 in A first phylogenomic hypothesis for Eulophidae (Hymenopteraı Chalcidoidea)
Figure 1. Phylogenetic relationships among eulophids inferred from 879 UCEs.
The biotic interactions hypothesis partially explains bird species turnover along a lowland Neotropical precipitation gradient
<p><span><span><span><span><span><span><span><span><span><span><span><b>Aim</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>We evaluated the influence of climate in determining bird communities along precipitation gradients. We argue that mechanisms responsible for community turnover along precipitation gradients are similar to mechanisms operating along temperature and latitudinal gradients. We test the hypothesis that environmental conditions affect community composition in dry forests, whereas biotic interactions affect community composition in wet forests.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Location</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>Low-elevation forests along a precipitation gradient in Colombia where precipitation ranges from 700 – 4000 mm annually but neither temperature or elevation change.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Time period</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>Present day</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Major Taxa Studied</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>Tropical Forest Birds.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Methods</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>We performed 291 bird counts in nine study areas across the ~3000 mm range of variation in precipitation. In each locality we obtained climatic characteristics, and a phylogenetic, morphological and physiological proxy data set to test predictions about the evolutionary relationships and distribution of traits in each community. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><b>Results</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>Bird communities changed abruptly along the precipitation gradient and could be divided into dry and wet forest communities. Analyses of phylogenetic relationships, trait space, and observations at nests suggested that environmental filtering is more important in dry forest, especially for breeding. In contrast, we found little evidence that competition was more important in wet forest. Nest predation or competition for nest space, however, may be more critical in wetter forests.</span></span></span></span></span></span></span></span></span></span></span></p> <p class="author"><span><span><span><span><span><span><span><span><span><span><span><b>Conclusions</b></span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span>The two distinct bird communities we documented suggest that lowland precipitation gradients, where temperature is constant can be as important as temperature gradients in generating high beta diversity. We conclude that the breeding process in bird communities might be crucial for determining community assembly along environmental gradients. Given that recent population declines in tropical birds have been attributed to changes in precipitation, by understanding the mechanisms underlying community assembly along precipitation gradients our study may improve our ability to understand those declines and predict the effects of climate change on neotropical avifauna.</span></span></span></span></span></span></span></span></span></span></span></p>
Darwin's vexing contrivance: A new hypothesis for why some flowers have two kinds of anther
<p>Heteranthery, the presence of two or more anther types in the same flower, is taxonomically widespread among bee-pollinated angiosperms, yet has puzzled botanists since Darwin. We test two competing hypotheses for its evolution: the longstanding "division of labour" hypothesis, which posits that some anthers are specialized as food rewards for bees whereas other are specialized for surreptitious pollination, and our new hypothesis that heteranthery is a way to gradually release pollen that maximizes pollen delivery. We examine the evolution of heteranthery and associated traits across the genus <i>Clarkia </i>(Onagraceae) and study plant-pollinator interactions in two heterantherous <i>Clarkia </i>species. Across species, heteranthery is associated with bee pollination, delayed dehiscence and colour crypsis of one anther whorl, and movement of that anther whorl upon dehiscence. Our mechanistic studies in heterantherous species show that bees notice, forage on, and export pollen from each anther whorl when it is dehiscing, and that heteranthery promotes pollen export. We find no support for division of labour, but multifarious evidence that heteranthery is a mechanism for gradual pollen presentation that likely evolved through indirect male-male competition for siring success.</p>
Overyielding in young tree communities does not support the stress-gradient hypothesis and is favoured by functional diversity and higher water availability
<p class="CxSpFirst"><strong>Summary:</strong></p> <ol> <li class="CxSpMiddle">Biodiversity effects on productivity and other ecosystem functions are strongly dependent on climate and resource availability. Based on the stress-gradient hypothesis, under conditions of greater abiotic stress, diversity effects on plant performance are intensified due to the increased relative importance of positive plant interactions. However, whether this hypothesis is consistently applicable in forest systems remains unclear. A field trial was established to test the stress-gradient hypothesis and examine diversity effects on aboveground biomass production of young trees in mixtures exposed to different water availability.</li> <li class="CxSpMiddle">Six native tree species of northern temperate forests (<i>Acer saccharum</i>,<i> Betula papyrifera</i>,<i> Larix laricina</i>,<i> Picea glauca, Pinus strobus</i>,<i> and Quercus rubra</i>) were planted as monocultures and as mixtures of two, four, and six species. For five growing seasons, four replicates of each community were exposed to conditions of either low- or high-water availability created by rainfall exclusion and weekly irrigation, respectively. Growth-years 4 and 5 were significantly different when the climatic water balance of the growing seasons were compared. We tested the effects of functional diversity on: (1) total growth of mixtures under low- and high-water availability, and (2) annual growth in years 4 (higher water availability, 2017) and 5 (lower water availability, 2018).</li> <li class="CxSpMiddle">Annual growth of most species in both years was greater under high- vs. low-water availability. Functional diversity had a significant positive effect on total biomass production and annual growth, and this effect was more strongly expressed under high-water availability. Functional diversity effects on annual growth did not differ between years 4 and 5 regardless of their climatic water balance. Functional and species identity were key to understanding productivity responses to mixture and treatment effects.</li> <li class="CxSpMiddle"> <i>Synthesis</i>: Contrary to the stress-gradient hypothesis, the positive effects of functional diversity on productivity were enhanced by high-water availability and were independent of seasonal water balance.</li> </ol>
Novel Tests of the Key Innovation Hypothesis: Adhesive Toepads in Arboreal Lizards
Abstract The evolution of key innovations—unique features that enable a lineage to interact with the environment in a novel way—may drive broad patterns of adaptive diversity. However, traditional tests of the key innovation hypothesis, those which attempt to identify the evolutionary effect of a purported key innovation by comparing patterns of diversity between lineages with and without the key trait, have been challenged on both conceptual and statistical grounds. Here, we explore alternative, untested hypotheses of the key innovation framework. In lizards, adhesive toepad structures increase grip strength on vertical and smooth surfaces such as tree trunks and leaves and have independently evolved multiple times. As such, toepads have been posited as a key innovation for the evolution of arboreality. Leveraging a habitat use dataset applied to a global phylogeny of 2692 lizard species, we estimated multiple origins of toepads in three major clades and more than 100 origins of arboreality widely across the phylogeny. Our results suggest that toepads arise adaptively in arboreal lineages and are subsequently rarely lost while maintaining arboreal ecologies. Padless lineages transition away from arboreality at a higher rate than those with toepads, and high rates of invasion of arboreal niches by non-arboreal padbearing lineages provides further evidence that toepads may be a key to unlocking evolutionary access to the arboreal zone. Our results and analytical framework provide novel insights to understand and evaluate the ecological and evolutionary consequences of key innovations.
Data from: Genomic data reject the hypothesis of sympatric ecological speciation in a clade of Desmognathus salamanders
Closely related taxa with dissimilar morphologies are often considered to have diverged via natural selection favoring different phenotypes. However, some studies have found these scenarios to be paired with limited or no genetic differentiation. Desmognathus quadramaculatus and D. marmoratus are sympatric salamander species thought to represent a case of ecological speciation based on distinct morphologies, but the results of previous studies have not resolved corresponding patterns of lineage divergence. Here, we use genome-wide data to test this hypothesis of ecological speciation. Population structure analyses partitioned individuals geographically, but not morphologically, into two adjacent regions of western North Carolina: Pisgah and Nantahala. Phylogenetic analyses confirmed the nominal species are non-monophyletic and resolved deep divergence between the two geographic clusters. Model-testing overwhelmingly supported the hypothesis that lineage divergence followed geography. Finally, ecological niche modeling showed that Pisgah and Nantahala individuals occupy different climatic niches, and geographic boundaries for the two lineages correspond to a difference in precipitation regimes across southern Appalachia. Overall, we reject the previous hypothesis of ecological speciation based on microhabitat partitioning. Instead, our results suggest that there are two cryptic lineages, each containing the same pair of morphotypes.
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
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.