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1,245 results for “hypothesis”
Figure 6 in Taxonomic revision and phylogenetic hypothesis for the jumping spider subfamily Ballinae (Araneae, Salticidae)
Figure 6. Baviola braueri (MRAC 143.138). Epigynum, ventral view. Scale bar = 0.2 mm.
Data from: A test of the competitive ability – cold tolerance trade-off hypothesis in seasonally breeding beetles
<p><span>Closely related species that use similar resources often differ in their seasonal patterns of activity, but the factors that limit their distributions across seasons are unknown for most species. One hypothesis to explain seasonal variation in the distributions of species involves a trade-off between competitive ability and cold tolerance, where tolerance to the cold compromises competitive ability in warmer (benign) temperatures, either at the level of the individual or population.</span></p> <p><span>We tested both individual-level and population-level mechanisms of this hypothesis in two co-occurring species of temperate burying beetles (Silphidae: <em>Nicrophorus sayi</em>, <em>N. orbicollis</em>) that differ in their seasonal patterns of activity.</span></p> <p><span>We measured cold tolerance, breeding activity as a function of temperature, and competitive ability as a function of temperature and season.</span></p> <p><span>Consistent with our hypothesis, the mid-season <em>N. orbicollis</em> was less able to function at the cold temperatures that characterize early spring, when the early-season <em>N. sayi</em> is most active. The larger beetle, however, always won one-on-one competitive trials at warm temperatures, regardless of species, inconsistent with an individual-level trade-off. <em>N. orbicollis</em> was usually larger and successful when competing for the same carrion later in the season, mostly because of its larger population size, consistent with a trade-off between competitive ability and cold tolerance acting at the population level.</span></p> <p><span>Our findings suggest that cold temperatures limit the mid-season <em>N. orbicollis</em> from earlier spring emergence, while competitive pressure from the more abundant, larger <em>N. orbicollis</em> constrains the early-season <em>N. sayi</em> from remaining active through the summer.</span></p>
The phoenix hypothesis of speciation
<p>Genetic divergence among allopatric populations builds reproductive isolation over time. This process is accelerated when populations face a changing environment, but abrupt change also places populations at risk of extinction. Here we use simulations of Fisher's geometric model with explicit population dynamics to explore the genetic changes that occur in the face of environmental changes. We show that evolutionary rescue leads to the fixation of mutations whose effects are larger on average and that these mutations are more likely to lead to reproductive isolation, compared with populations not at risk of extinction. We refer to the formation of new species from the ashes of populations in decline as the phoenix hypothesis of speciation. The phoenix hypothesis predicts more substantial hybrid fitness breakdown among populations surviving a higher extinction risk. The hypothesis was supported when many loci underlie adaptation. When, however, there was only a small number of potential rescue mutations, we found that mutations fixed in different populations were more likely to be identical, with parallel changes reducing isolation. With a limited genomic potential for adaptation, we find support for a modified version of the phoenix hypothesis where reproductive isolation builds fastest in populations subject to an intermediate extinction risk.</p>
Spatiotemporal predictions of the alternative prey hypothesis: Predator habitat use during decreasing prey abundance
<p>The alternative prey hypothesis supposes that predators supported by a primary prey species will shift to consume alternative prey during a decrease in primary prey abundance. The hypothesis implies that during declines of one prey species, a predator modifies their behavior to exploit a secondary, or alternative, species. Despite occurring in many systems, the behavioral mechanisms (e.g., habitat selection) allowing predators to shift toward alternative prey during declines in the abundance of their primary prey are poorly understood. We evaluated habitat selection and use by a generalist predator with respect to two prey species during a dramatic decrease in the abundance of primary prey. Further, we evaluated how spatial variation in access to primary prey affected habitat selection and assessed similarity and overlap between habitats used by each prey species. Coyotes (<em>Canis</em> <em>latrans</em>) exhibited decreasing selection for cottontail rabbits (<em>Sylvilagus</em> spp.; primary prey) during population decreases but did not shift habitat selection toward neonate mule deer (<em>Odocoileus</em> <em>hemionus</em>; alternative prey). Use of rabbit habitat remained high even during historically low rabbit abundance, while mule deer habitat was used in proportion to its availability. Coyotes seemingly do not make large shifts in habitat selection toward alternative prey following spatial and temporal decreases in the abundance of primary prey, but instead, take advantage of habitat overlap to facilitate prey-switching behavior. Our work extends previous research conducted under the alternative prey hypothesis by explicitly evaluating the influence of habitat overlap between prey species and variation in access to prey habitat as factors affecting prey-switching behaviors in predators.</p>
Data for: The climatic variability hypothesis and trade–offs in thermal performance in coastal and inland populations of Mimulus guttatus
<p>Ecologists and evolutionary biologists have long predicted that organisms in more climatically variable environments should be adapted to handle a wider range of conditions. This intuitive idea, known as the Climatic Variability Hypothesis, has gained mixed support from empirical studies. We tested the Climatic Variability Hypothesis in a novel system by comparing the thermal breadth of coastal and inland populations of <em>Mimulus guttatus</em>. To quantify thermal breadth, we performed a thermal performance experiment and built performance curves. Using these performance curves, we also evaluated evidence for a breadth–performance trade–off and the Hotter–is–Better hypothesis. We did not find support for the Climatic Variability Hypothesis; coastal and inland populations did not differ in thermal breadth. However, we found evidence for a breadth performance trade–off and the Hotter–is–Better hypothesis. Surprisingly, the two most inland populations differed the most in the thermal performance traits we evaluated. Our results highlight the importance of explicitly measuring thermal performance to test explanations of species distribution patterns and the need to examine alternative mechanisms by which organisms occupy different climatic regimes.</p>
An omnivore vigor hypothesis? Nutrient availability strengthens herbivore suppression by omnivores across 48 field sites
<ol> <li>Nutrients regulate herbivore growth from the 'bottom-up' via improved plant vigor and food quality. Nitrogen also affects 'top-down' control of herbivores by moderating attraction of predators and the rates at which they consume herbivorous prey.</li> <li>Tri-trophic consequences of nitrogen availability are more challenging to predict among omnivorous natural enemies who feed on both plants and herbivores, limiting our ability to predict net outcomes of nutrient availability in food webs.</li> <li>In a two-year field survey of insects on zucchini host plants at 48 sites, I predicted that both herbivores and foliar-feeding omnivores would increase with nutrient availability, while predators would not.</li> <li>My results revealed positive relationships between omnivores and foliar nitrogen concentrations, while predators had neutral responses to foliar N. Surprisingly, herbivores declined with increasing foliar N across the field sites.</li> <li>Greenhouse experiments reinforced these patterns, as herbivore growth inversely correlated with soil N concentrations in communities that included foliar-feeding omnivores. Conversely, herbivore growth was uncorrelated with soil N on plants with generalist predators, nor on predator-free plants.</li> <li>These results suggest that omnivores mount strong and consistent responses to nitrogen in plant tissues in a variety of ecological contexts. In environments where omnivorous arthropods can thrive, their recruitment to nitrogen-rich plants may increase predation and thereby counterbalance and stabilize 'bottom-up' increases in herbivore performance supported by enhanced foliar nutrition.</li> </ol>
A unified meta-ecosystem dynamics model: Integrating herbivore-plant subwebs with the intermittent upwelling hypothesis
<p>Determining the relative influence of biotic and abiotic processes in structuring communities at local to large spatial scales is best understood using a biogeographic comparative-experimental approach. Using this approach, previous work suggests that intertidal community dynamics (top-down and bottom-up effects) vary unimodally along an upwelling-based productivity gradient, termed the Intermittent Upwelling Hypothesis (IUH). Evidence consistent with the IUH comes from the sessile invertebrate/predator (SIP) subweb in certain rocky intertidal communities, but whether this pattern extends to macrophyte/herbivore (MH) subwebs is unknown. Here we ask: Are MH subwebs also structured as predicted by the IUH? What is the relative importance of herbivory and predation in structuring these communities? Under what conditions do ecological subsidies like nutrients or propagule production drive community dynamics? And are omnivorous interactions important? We hypothesize that MH subwebs are driven by a new construct, the Grazing-Weakening Hypothesis (GWH), which states that MH interactions weaken monotonically with increasing nutrients, with strong (weak) herbivory and low (high) macrophyte productivity at low (high) nutrients. We explored local-to-large spatial scale dynamics of both subwebs using a biogeographic comparative-experimental factorial field experiment testing joint and separate effects of herbivores and predators between two continents. Experiments at ten sites ranging across from persistent upwelling to persistent downwelling regimes ran for 26-29 months in Oregon and California, and New Zealand South Island. For the MH subweb, results were consistent with the GWH: herbivory declined and macrophytes increased with increasing nutrients. As expected, results for the SIP subweb were consistent with the IUH: predator effect size was unimodally related to upwelling. Overall, herbivory explained more variation in community structure than did predation, especially in New Zealand. Omnivory was weak, sessile invertebrates outcompeted macrophytes, and ocean-driven subsidies provided the basic template driving ecosystem dynamics. We propose a unified Meta-Ecosystem Dynamics Model (MEcoDynaMo) combining MH and SIP results: with increased upwelling, sessile invertebrates and underlying dynamics vary unimodally (as in the IUH), while herbivory decreases and macrophytes generally increase. While this model was based on research in temperate ecosystems varying in upwelling regime, its wider applicability remains to be tested.</p>
Data from: Evidence for the Predator Attraction Hypothesis in an amphibian predator-prey system
<p>Many species possess damage-released chemical alarm cues that function in alerting nearby individuals to a predator attack. One hypothesis for the evolution and/or maintenance of such cues is the Predator Attraction Hypothesis, where predators, rather than prey, are the 'intended' recipients of these cues. If a predator attack attracts additional predators, these secondary predators might interfere with the predation event, providing the prey with a better chance to escape. In this study, we conducted two experiments to explore this hypothesis in an amphibian predator/prey system. In Experiment 1, we found that tiger salamanders (<em>Ambystoma</em> <em>mavortium</em>) showed a foraging attraction to chemical cues from wood frog (<em>Lithobates</em> <em>sylvaticus</em>) tadpoles. Salamanders that were experienced with tadpole prey, in particular, were strongly attracted to tadpole alarm cues. In Experiment 2, we observed experimental encounters between a tadpole and either one or two salamanders. The presence of the second predator caused salamanders to increase attack speed at the cost of decreased attack accuracy (i.e., increasing the probability that the tadpole would escape attacks). We also found that the mere presence of visual and chemical cues from a second predator did not affect this speed/accuracy trade-off but did cause enough of a distraction to increase tadpole survival. Thus, our findings are thus consistent with the Predator Attraction Hypothesis for the evolution and/or maintenance of alarm cues.</p>
Trans-eQTL effects on risk of type 1 diabetes: a test of the sparse effector (omnigenic) hypothesis of complex trait genetics (supplementary data)
<p>This repository contains summary-level data generated by performing <a href="https://github.com/molepi-precmed/trans-qtls">Genomewide aggregated trans- effects (GATE) analysis</a> in case-control study of Type 1 Diabetes (T1D).</p>
Temperate zone isolation by climate: an extension of Janzen's 1967 hypothesis
<p>One of the most stunning patterns of the distribution of life on Earth is the latitudinal biodiversity gradient. In an influential paper, Janzen (1967) predicted that tropical mountains are more effective migration barriers than temperate mountains of the same elevation because annual temperature variation in the tropics is lower. A great deal of research has demonstrated that the mechanism envisioned by Janzen operates at broad latitudinal scales. However, the extent that the mechanism mediates biodiversity generally, and at smaller scales, is far less understood. We investigated if climate overlap is associated with genetic similarity between populations within temperate regions using lizards in the Sierra Nevada mountain range, California, as a study system. By comparing genetic differentiation between high- and low-elevation populations, we found that in addition to the expected strong pattern of isolation by distance (IBD), climate overlap values were negatively associated with genetic differentiation, indicating that population pairs that inhabit climatically similar environments are less genetically differentiated. Moreover, while climate overlap between high- and low-elevation sites is predicted to increase from the equator to temperate regions, we find that in adjacent mountain ranges at the same latitude in temperate regions, climate overlap values can vary widely. This study suggests that in addition to the well-studied main effect of latitude on climate overlap and population differentiation, local climate factors within bioclimatic regions can also influence genetic differentiation between populations, and do so by the same general mechanism that operates at larger geographic scales.</p>
Data from: A test of the green wave hypothesis in omnivorous brown bears across North America
<p>Herbivorous animals tend to seek out plants at intermediate phenological states to improve energy intake while minimizing consumption of fibrous material. In some ecosystems, the timing of green-up is heterogeneous and propagates across space in a wave-like pattern, known as the green wave. Tracking the green wave allows individuals to prolong access to higher-quality forage. While there is a plethora of empirical support for such behavior in herbivorous taxa, the green wave hypothesis (GWH) is nuanced based on factors such as body morphometrics and digestive capacity. Furthermore, little is known about whether other taxa, such as omnivores, track the green wave. Our objective was to assess whether the GWH can be extended to explain the movements of omnivores. Using GPS collar data from seven populations (n = 127 individuals) of brown bears (<em>Ursus</em> <em>arctos</em>) across their entire North American range, we first tested whether bears tracked the green wave. Using conditional resource selection functions, we found that variation in proxies of vegetative forage quality better-explained movement and habitat selection than proxies of forage biomass in over half of the bears in our study, providing evidence of green wave tracking. Second, we assess factors that explained variation in green wave tracking using linear mixed-effects models. Green wave tracking in brown bears was explained by the variation in availability of green-up within spring home ranges, and how green-up transitioned across those home ranges. Our results demonstrate that the GWH can partially explain movement of a non-migratory omnivorous species, extending the generality of the GWH as a broad predictor of animal space use. The green wave is another resource wave brown bears track, and our findings help predict brown bear space use, which can be used to guide conservation and habitat restoration efforts.</p>
Data from: Variation in the strength of female mate preference for male size supports the signal reliability hypothesis
<p>Both sexually selected traits and mate preferences for these traits can be condition dependent, yet how variation in preferred traits could select for condition dependent preferences has rarely been examined. The signal reliability hypothesis predicts that mate preferences vary across environments in relation to the reliability of the information preferred traits provide in those environments. Extensive variation in copy number of the <em>mc4r</em> gene on Y chromosome is correlated with adult male size in <em>Xiphophorus multilineatus</em>, when males stop growing. This genetic variation allowed us to use a split-sibling design to show that male size is more variable, and thus likely to provide reliable information about male genotype, when males were reared in a warm as compared to cold environment. Females reared in the warm environment had stronger mate preferences for male size. Understanding how the reliability of male traits can select for conditional variation in the strength of the female mate preferences will further our discovery of adaptive mate preferences. For example, the relationship between the strength of a female's mate preference and their growth rates supports previous work hypothesizing disassortative mating in relation to growth rates to mitigate a documented growth-mortality tradeoff in this species.</p>
Adverse Effects of RBC Transfusions: A Unifying Hypothesis
ClinicalTrials.gov study NCT00838331. IPD Sharing: Not stated. Countries: 1. Publications: 2.
Tofacitinib Hypothesis-generating, Pilot Study for Corticosteroid-Dependent Sarcoidosis
ClinicalTrials.gov study NCT03793439. IPD Sharing: YES. Countries: 1. Publications: 2.
Fungi and deadwood diversity: A test of the area-heterogeneity trade-off hypothesis
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Rainfall seasonality shapes belowground root trait dynamics in an Amazonian tropical rainforest: A test of the stress-dominance hypothesis
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Out of the temperate zone: a phylogenomic test of the biogeographical conservatism hypothesis in a contrarian clade of ants (Hymenoptera: Formicidae: Stenammini)
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Function of juvenile plumage in the northern goshawk (Accipiter gentilis): Aggressive mimicry hypothesis
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Data from: Neighbor density and post-contact immobility duration as antipredator behavior: Antlion larvae do not fit the selfish prey hypothesis
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Data from: Testing the adaptive hypothesis of Batesian mimicry among hybridizing North American admiral butterflies
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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.