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795 results for “fluctuations”
Anticipating fluctuations of bigeye tuna in the Pacific Ocean from three-dimensional ocean biogeochemistry
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Data from: breeding under pressure: corticosterone is associated with reproductive investment under fluctuating predation risk in a long-lived sea duck
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Electrochemically controlled switching of dyes for enhanced super-resolution optical fluctuation imaging (EC-SOFI)
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Data from: Phenotypic plasticity and the effects of thermal fluctuations on specialists and generalists
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Corals adapted to extreme and fluctuating seawater pH increase calcification rates and have unique symbiont communities
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Data from: Understanding density fluctuations in supersonic, isothermal turbulence
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Data from: Niche partitioning between river shark species is driven by seasonal fluctuations in environmental salinity
<ol> <li>Tropical rivers and estuaries are highly dynamic environments, where environmental conditions change dramatically over spatial and temporal scales. This creates both physiological and ecological challenges for euryhaline elasmobranchs, where fluctuations in salinity can impact not only osmoregulatory function, but also the ability to find and acquire prey.</li> <li>We investigated how spatial and temporal variation in environmental salinity influences physiological homeostasis, habitat utilisation, and migration timing in two euryhaline carcharhinid sharks within a tropical river in northern Australia. Neonate and juvenile bull sharks <i>Carcharhinus leucas</i> and speartooth sharks <i>Glyphis glyphis </i>were tracked over a four-year period using implanted acoustic tags and an array of hydrophone receivers. Tissue samples were also collected from captured sharks and analysed for interspecific differences in plasma osmolarity, urea and electrolyte (Na<sup>+ </sup>and K<sup>+</sup>) concentrations, and the stable isotopes δ<sup>13</sup>C and δ<sup>15</sup>N.</li> <li>We discovered that immature <i>C. leucas</i> and <i>G. glyphis</i> segregate spatially along a salinity gradient between September and December, where the mean volume of intersection between species dropped as low as 0.01. While<i> G. glyphis</i> used higher salinity environments (mean salinity = 19.22) located between 30 and 70 km from the mouth of the estuary, <i>C. leucas</i> occupied freshwater reaches (mean salinity = 1.98) between 60 and 110 km upstream. Plasma osmolarities of both species were always hyperosmotic to the environment, with electrolyte concentrations maintained within a narrow range independent of environmental osmolarities. At the onset of the wet season, both <i>C. leucas</i> and <i>G. glyphis</i> undertook a coordinated downstream migration towards the lower estuary before returning upstream.</li> <li> <i>C. leucas</i> blood tissues were more enriched in δ<sup>15</sup>N and δ<sup>13</sup>C than samples collected from similar size <i>G. glyphis</i>, suggesting that these species not only spatially segregate within low salinity habitats but also prey on different dietary resources. Furthermore, a loss of enriched isotopic values in fin tissue with increasing body length provides further support for marine-use by adult sharks in conjunction with dependence on rivers as important nursery habitat. Our results illustrate the importance of long-term integrative studies into resource competition and the significance of discrete brackish habitats for threatened euryhaline elasmobranchs. </li> </ol>
Codes and datasets associated with the paper "On the dissipation rate of temperature fluctuations in stably stratified flows"
<p>Here, you will find some of the codes and datasets utilized in the article: "On the dissipation rate of temperature fluctuations in stably stratified flows". (<a href="https://arxiv.org/abs/2001.06369">https://arxiv.org/abs/2001.06369</a>)</p> <p>The direct numerical simulations were performed using the HERCULES code (<a href="https://github.com/friedenhe/HERCULES">https://github.com/friedenhe/HERCULES</a>). For all the simulations, the bulk Reynolds number is kept at 20,000. The bulk Richardson number is varied from 0.1 to 0.5. The zip files Re20000RiXX.zip contains the various turbulence statistics. </p> <p>Re20000Ri10: Ri_b = 0.1</p> <p>Re20000Ri20: Ri_b = 0.2</p> <p>Re20000Ri30: Ri_b = 0.3</p> <p>Re20000Ri40: Ri_b = 0.4</p> <p>Re20000Ri50: Ri_b = 0.5</p> <p>Every dat file (within the zip archives) is in ascii format and has 10 rows and 286 columns. Each row corresponds to normalized time (ranging from 1 to 10). Each column represents vertical model levels. </p>
Representation model of wind velocity fluctuations and saltation sand transport in aeolian sand flow
<p>The data of the figures in the article.</p>
Data from: Individualistic evolutionary responses of central African rain forest plants to Pleistocene climatic fluctuations
<p>Understanding the evolutionary dynamics of genetic diversity is fundamental for species conservation in the face of climate change, particularly in hyper-diverse biomes. Species in a region may respond similarly to climate change, leading to comparable evolutionary dynamics, or individualistically, resulting in dissimilar patterns. The second largest expanse of continuous tropical rain forest (TRF) in the world is found in Central Africa. Here, present-day patterns of genetic structure are thought to be dictated by repeated expansion and contraction of TRFs into and out of refugia during Pleistocene climatic fluctuations. This refugia model implies a common response to past climate change. However, given the unrivalled diversity of TRFs, species could respond differently because of distinct environmental requirements or ecological characteristics. To test this we generated genome-wide sequence data for >750 individuals of seven co-distributed plants from Lower Guinea in Central Africa. We inferred species' evolutionary and demographic histories within a comparative phylogeographic framework. Levels of genetic structure varied among species and emerged primarily during the Pleistocene, but divergence events were rarely concordant. Demographic trends ranged from repeated contraction and expansion to continuous growth. Furthermore, patterns in genetic variation were linked to disparate environmental factors including climate, soil and habitat stability. Using a strict refugia model to explain past TRF dynamics is too simplistic. Instead, individualistic evolutionary responses to Pleistocene climatic fluctuations have shaped patterns in genetic diversity. Predicting the future dynamics of TRFs under climate change will be challenging and more emphasis is needed on species ecology to better conserve TRFs worldwide.</p>
Assessing the impact of static and fluctuating ocean acidification on the behavior of Amphiprion percula
<p>Attached is the complete raw data from Vaughan and Dixson 2021 ‘Assessing the impact of static and fluctuating ocean acidification on the behavior of <em>Amphiprion percula</em>’. </p> <p>Data collected from the behavioral lateralization trials has been inputted into the file ‘Vaughan_2020_Lateralization_Raw’. Column A indicate the CO<sub>2</sub> treatment group, where “SPD” = Static Present Day, “SFD” = Static Future Day, “FPD” = Fluctuating Present Day, and “FFD” = Fluctuating Future Day. Each individual fish used from each treatment group (n=30) is displayed in Column B. Column C shows the binary results, in order, of each fish’s turns in the T-maze, and was scored as 0 (right turn) or 1 (left turn) for a total of 10 turns. The total number of turns to the right and left are provided in Column D-E. The relative lateralization (<em>L</em><sub>R</sub>) of each fish was calculated {L<sub>R</sub> = [(Turn to the right – Turn to the left)/(Turn to the right + Turn to the left)] ∗ 100} in Column F. Absolute lateralization (<em>L</em><sub>A</sub>) is provided in Column G.</p> <p>Chemosensory response data has been inputted into the file ‘Vaughan_2020_Chemosensory_Raw’. Column A and B display treatment group and fish ID (n=20) as outlined above. The cue used in trial of either Tang (nonpredator) or Cod (predator) is provided in Column C, and the control in Column D. Numbers in these are used solely for the purpose of data analysis. The side of the cue in the flume is provided in Column E, and corresponds with the cue labelled in Column C. Buckets containing either the cue or control were placed above the flume and color coded as “BS” (blue side) and “RS” (red side), as the person scoring the trials was blinded. This also helped account for the switch (from one side of the flume to the other) that occurs halfway through each trial. Columns F-G represent results from the first 2min recording period, and Columns H-I represent results from the second 2min recording period. The total tallies from each fish are provided in Column J; the totals from each side are calculated in Columns K-L, and then sorted by either cue or control in Columns M-N. Proportions and percentages in cue and control are calculated and provided in Columns O-P and Q-R, respectively. </p> <p>Carbonate chemistry data is compiled and provided in the ‘Vaughan_2020_Carbonate_Chemistry’. Measurements were taken each week (Column A) of each treatment group (as stated above, Column B). Column C reflects the time recordings were taken in the fluctuating treatments to hit the high, mid and low CO<sub>2</sub> points at “6:30”, “12:30” and “18:30”. Measurements of static treatment groups were taken at randomly selected times to get the reflection of the carbonate chemistry of these treatments, but for the purpose of clarity in this document they are listed as “Static”. Measurements were taken from a subset of tanks each that rotated each week (Column D). Our target pH<sub>NBS</sub> values (i.e. what was programmed into the APEX System) are listed in Column E. Columns F-H displayed pH<sub>NBS</sub> (taken with APEX probes), temperature °C (taken with a portable Mettler Toledo probe) and salinity (taken with a refractometer). Water samples were analyzed spectrophotometrically to provide pH<sub>T</sub> and dissolved inorganic carbon, with values provided in Columns I-J. Using the program CO2SYS, total alkalinity and <em>p</em>CO<sub>2</sub> were calculated, with values provided in Columns K-L.</p>
Impact of Pleistocene eustatic fluctuations on evolutionary dynamics in Southeast Asian biodiversity hotspots
Pleistocene Climatic Fluctuations (PCF) are frequently highlighted as important evolutionary engines that triggered cycles of biome expansion and contraction. While there is ample evidence of the impact of PCF on biodiversity for continental biomes, the consequences in insular systems depend on the geology of the islands and the ecology of the taxa inhabiting them. The idiosyncratic aspects of insular systems are exemplified by the islands of the Sunda Shelf in Southeast Asia (Sundaland), where PCF-induced eustatic fluctuations had complex interactions with the geology of the region, resulting in high species diversity and endemism. Emergent land in Southeast Asia varied drastically with sea level fluctuations during the Pleistocene. Climate-induced fluctuations in sea level caused temporary connections between insular and continental biodiversity hotspots in Southeast Asia. These exposed lands likely had freshwater drainage systems that extended between modern islands: the Paleoriver Hypothesis. Built upon the assumption that aquatic organisms are among the most suitable models to trace ancient river boundaries and fluctuations of landmass coverage, the present study aims to examine the evolutionary consequences of PCF on the dispersal of freshwater biodiversity in Southeast Asia. Time-calibrated phylogenies of DNA-delimited species were inferred for six species-rich freshwater fish genera in Southeast Asia (Clarias, Channa, Glyptothorax, Hemirhamphodon, Dermogenys, Nomorhamphus). The results highlight rampant cryptic diversity and the temporal localization of most speciation events during the Pleistocene, with 88% of speciation events occurring during this period. Diversification analyses indicate that sea level-dependent diversification models poorly account for species proliferation patterns for all clades excepting Channa. Ancestral area estimations point to Borneo as the most likely origin for most lineages, with two waves of dispersal to Sumatra and Java during the last 5 Myrs. Speciation events are more frequently associated with boundaries of the paleoriver watersheds, with 60%, than islands boundaries, with 40%. In total, one-third of speciation events are inferred to have occured within paleorivers on a single island, suggesting that habitat heterogeneity and factors other than allopatry between islands substantially affected diversification of Sundaland fishes. Our results suggest that species proliferation in Sundaland is not wholly reliant on Pleistocene sea-level fluctuations isolating populations on different islands.
Replication package for: Recoverability and Expectations-Driven Fluctuations
<p>This package contains all the data and code necessary to reproduce the results in Chahrour and Jurado, "Recoverability and Expectations-Driven Fluctuations." Review of Economic Studies (forthcoming). </p>
Maternal provisioning and fluctuating thermal regimes enhance immune response in a reptile with temperature-dependent sex determination
<p>The Charnov-Bull model of differential fitness is often used to explain the evolution and maintenance of temperature-dependent sex determination (TSD). Most tests of the model focus on morphological proxies of fitness, such as size traits, whereas early life physiological traits that are closely related to lifetime fitness might provide a framework for generalising the Charnov-Bull model across taxa. One such trait is the strength of early life immune response, which is strongly linked to early life survival and fitness. Here, we manipulate temperature, variance in temperature, and sex to test the Charnov-Bull model using a physiological trait, immune system strength, in the snapping turtle (<i>Chelydra serpentina </i>L. 1758). We find no evidence of sex-specific differences in bactericidal capacity of hatchling blood, and no evidence that mean temperature influences bactericidal capacity. However, we find that fluctuating incubation temperature (i.e., a more naturalized incubation regime) is associated with a greater bactericidal capacity compared to constant temperature incubation. We also find that egg mass, a proxy for maternal provisioning, is positively associated with bactericidal capacity. Our findings suggest that the evolution of temperature-dependent sex determination in reptiles is unrelated to our measure early-life innate immunity. Our study also underlines how immune response is condition-dependent in early life, and questions the biological relevance of constant temperature incubation in experimental studies on ectotherm development.</p>
Data from: Demographic responses of a site-faithful and territorial predator to its fluctuating prey: long-tailed skuas and arctic lemmings
1. Environmental variability, through interannual variation in food availability or climatic variables, is usually detrimental to population growth. It can even select for constancy in key life-history traits, though some exceptions are known. Changes in the level of environmental variability are therefore important to predict population growth or life-history evolution. Recently, several cyclic vole and lemming populations have shown large dynamical changes, that might affect rodent predator demography or life histories. 2. Skuas constitute an important case study among rodent predators, because of their strongly saturating breeding productivity (they lay only two eggs) and high degree of site fidelity, in which they differ from nomadic predators raising large broods in good rodent years. This suggests that they cannot capitalize on lemming peaks to the same extent as nomadic predators, and might be more vulnerable to collapses of rodent cycles. 3. We develop a model for the population dynamics of long-tailed skuas feeding on lemmings to assess the demographic consequences of such variable and nonstationary prey dynamics, based on data collected in NE Greenland. The model shows that populations of long-tailed skua sustain well changes in lemming dynamics, including temporary collapses (e.g. 10 years). A high floater-to-breeder ratio emerges from rigid territorial behaviour and a long life expectancy, which buffers the impact of adult abundance's decrease on the population reproductive output. 4. The size of the floater compartment is affected by changes in both mean and coefficient of variation of lemming densities (but not cycle amplitude and periodicity per se). In Greenland, the average lemming density is below the threshold density required for successful breeding (including during normally cyclic periods). Due to Jensen's inequality, skuas therefore benefit from lemming variability; a positive effect of environmental variation. 5. Long-tailed skua populations are strongly adapted to fluctuating lemming populations, an instance of demographic lability in the reproduction rate. They are also little affected by poor lemming periods, if there are enough floaters, or juveniles disperse to neighbouring populations. The status of Greenland skua populations therefore strongly depends upon floater numbers and juvenile movements, which are not known. This reveals a need to intensify colour-ringing efforts on the long-tailed skua at a circumpolar scale.
Data from: Fluctuating asymmetry in Menidia beryllina before and after the 2010 DeepWater Horizon oil spill
Assessing the impacts of the Deepwater Horizon oil spill with a dependable baseline comparison can provide reliable insight into environmental stressors on organisms that were potentially affected by the spill. Fluctuating asymmetry (small, non-random deviations from perfect bilateral symmetry) is an informative metric sensitive to contaminants that can be used to assess environmental stress levels. For this study, the well-studied and common Gulf of Mexico estuarine fish, Menidia beryllina, was used with pre and post-oil spill collections. Comparisons of fluctuating asymmetry in three traits (eye diameter, pectoral fin length, and pelvic fin length) were made pre and post-oil spill across two sites (Old Fort Bayou and the Pascagoula River), as well as between years of collection (2011, 2012)-one and two years, respectfully, after the spill in 2010. We hypothesized that fluctuating asymmetry would be higher in post-Deepwater Horizon samples, and that this will be replicated in both study areas along the Mississippi Gulf coast. We also predicted that fluctuating asymmetry would decrease through time after the oil spill as the oil decomposed and/or was removed. Analyses performed on 1135 fish (220 pre and 915 post Deepwater Horizon) showed significantly higher post spill fluctuating asymmetry in the eye but no difference for the pectoral or pelvic fins. There was also higher fluctuating asymmetry in one of the two sites both pre and post-spill, indicating observed asymmetry may be the product of multiple stressors. Fluctuating asymmetry decreased in 2012 compared to 2011. Fluctuating asymmetry is a sensitive measure of sub lethal stress, and the observed variability in this study (pre vs. post-spill or between sites) could be due to a combination of oil, dispersants, or other unknown stressors.
Data from: Density dependence in demography and dispersal generates fluctuating invasion speeds
Density dependence plays an important role in population regulation and is known to generate temporal fluctuations in population density. However, the ways in which density dependence affects spatial population processes, such as species invasions, are less understood. Although classical ecological theory suggests that invasions should advance at a constant speed, empirical work is illuminating the highly variable nature of biological invasions, which often exhibit nonconstant spreading speeds, even in simple, controlled settings. Here, we explore endogenous density dependence as a mechanism for inducing variability in biological invasions with a set of population models that incorporate density dependence in demographic and dispersal parameters. We show that density dependence in demography at low population densities—i.e., an Allee effect—combined with spatiotemporal variability in population density behind the invasion front can produce fluctuations in spreading speed. The density fluctuations behind the front can arise from either overcompensatory population growth or density-dependent dispersal, both of which are common in nature. Our results show that simple rules can generate complex spread dynamics and highlight a source of variability in biological invasions that may aid in ecological forecasting.
Stochastic fluctuations in apoptotic threshold of tumor cells can enhance apoptosis and combat fractional killing
Fractional killing, which is a significant impediment to successful chemotherapy, is observed even in a population of genetically identical cancer cells exposed to apoptosis-inducing agents. This phenomenon arises not from genetic mutation but from cell-to-cell variation in the activation timing and level of the proteins that regulate apoptosis. To understand the mechanism behind the phenomenon, we formulate complex fractional killing processes as a first-passage time (FPT) problem with a stochastically fluctuating boundary. Analytical calculations are performed for the FPT distribution in a toy model of stochastic p53 gene expression, where the cancer cell is killed only when the p53 expression level crosses an activity apoptotic threshold. Counterintuitively, we find that threshold fluctuations can effectively enhance cellular killing by significantly decreasing the mean time that the p53 protein reaches the threshold level for the first time. Moreover, faster fluctuations lead to the killing of more cells. These qualitative results imply that dynamic variability in threshold is an unneglectable stochastic source, and can be taken as a strategy for combating fractional killing of cancer cells.
Negative frequency-dependent selection maintains coexisting genotypes during fluctuating selection
Natural environments are rarely static; rather selection can fluctuate on time scales ranging from hours to centuries. However, it is unclear how adaptation to fluctuating environments differs from adaptation to constant environments at the genetic level. For bacteria, one key axis of environmental variation is selection for planktonic or biofilm modes of growth. We conducted an evolution experiment with <i>Burkholderia cenocepacia</i>, comparing the evolutionary dynamics of populations evolving under constant selection for either biofilm formation or planktonic growth with populations in which selection fluctuated between the two environments on a weekly basis. Populations evolved in the fluctuating environment shared many of the same genetic targets of selection as those evolved in constant biofilm selection, but were genetically distinct from the constant planktonic populations. In the fluctuating environment, mutations in the biofilm-regulating genes wspA and rpfR rose to high frequency in all replicate populations. A mutation in wspA first rose rapidly and nearly fixed during the initial biofilm phase but was subsequently displaced by a collection of rpfR mutants upon the shift to the planktonic phase. The wspA and rpfR genotypes coexisted via negative frequency-dependent selection around an equilibrium frequency that shifted between the environments. The maintenance of coexisting genotypes in the fluctuating environment was unexpected. Under temporally fluctuating environments coexistence of two genotypes is only predicted under a narrow range of conditions, but the frequency-dependent interactions we observed provide a mechanism that can increase the likelihood of coexistence in fluctuating environments.
Data from: Linking niche theory to ecological impacts of successful invaders: insights from resource fluctuation-specialist herbivore interactions
1. Theories of species coexistence and invasion ecology are fundamentally connected and provide a common theoretical framework for studying the mechanisms underlying successful invasions and their ecological impacts. Temporal fluctuations in resource availability and differences in life-history traits between invasive and resident species are considered as likely drivers of the dynamics of invaded communities. Current critical issues in invasion ecology thus relate to the extent to which such mechanisms influence coexistence between invasive and resident species, and to the ability of resident species to persist in an invasive-dominated ecosystem. 2. We tested how a fluctuating resource and species traits differences may explain and help predict long-term impacts of biological invasions in forest specialist insect communities. We used a simple invasion system comprising closely related invasive and resident seed-specialized wasps (Hymenoptera: Torymidae) competing for a well-known fluctuating resource, and displaying divergent diapause, reproductive and phenological traits. 3. Based on extensive long-term field observations (1977-2010), we developed a combination of mechanistic and statistical models aiming to (i) obtain a realistic description of the population dynamics of these interacting species over time, and (ii) clarify the respective contributions of fluctuation-dependent and fluctuation-independent mechanisms to long-term impact of invasion on the population dynamics of the resident wasp species. 4. We showed that a fluctuation-dependent mechanism was unable to promote coexistence of the resident and invasive species. Earlier phenology of the invasive species was the main driver of invasion success, enabling the invader to exploit an empty niche. Phenology also had the greatest power to explain the long-term negative impact of the invasive on the resident species, through resource preemption. 5. This study provides strong support for the critical role of species differences in interspecific competition outcomes within animal communities. Our mechanisticstatistical approach allows disentangling the critical drivers of the dynamics of coexistence and exclusion within novel species assemblages, following both intentional and non-intentional species introductions.
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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.