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188 results for “explained variation”
Data from: Individual differences in behaviour explain variation in survival: a meta-analysis
<p>Research focusing on among-individual differences in behaviour ("animal personality") has been blooming for over a decade. One of the central theories explaining the maintenance of such behavioural variation posits that individuals expressing greater "risky" behaviours should suffer higher mortality. Here, for the first time, we synthesize the existing empirical evidence for this key prediction. Our results did not support this prediction as there was no directional relationship between riskier behaviour and greater mortality; however there was a significant absolute relationship between behaviour and survival. In total, behaviour explained a significant, but small, portion (5.8%) of the variance in survival. We also found that risky (versus "shy") behavioural types live significantly longer in the wild, but not in the laboratory. This suggests that individuals expressing risky behaviours might be of overall higher quality but the lack of predation pressure and resource restrictions mask this effect in laboratory environments. Our work implies that individual differences in behaviour explain important differences in survival but not in the direction predicted by theory. Importantly, this suggests that the models predicting survival trade-offs may need revision and/or empiricists may need to reconsider their proxies of risky behaviours when testing such theory.</p>
Data from: Nest predation risk explains variation in avian clutch size
Questions about the ecological drivers of, and mechanistic constraints on, productivity have driven research on life history evolution for decades. Resource availability and offspring mortality are considered among the two most important influences on the number of offspring per reproductive attempt. We used a factorial experimental design to manipulate food abundance and perceived offspring predation risk in a wild avian population (red-faced warblers; Cardellina rubrifrons) to identify the mechanistic cause of variation in avian clutch size. Additionally, we tested whether female quality helped explain the extant variation in clutch size. We found no support for the Food Limitation or Female Quality Hypotheses, but we did find support for both predictions of the Nest Predation Risk Hypothesis. Females that experienced an experimentally heightened perception of offspring predation risk responded by laying a smaller clutch than females in the control group. Additionally, predation rates at artificial nests were highest where red-faced warbler clutch size was smallest (at high elevations). Life history theory predicts that an individual should invest less in reproduction when high nest predation risk reduces the likely benefit from that nesting attempt, and indeed we found that birds exhibit phenotypic plasticity in clutch size by laying fewer eggs in response to increasing nest predation risk.
Differences in oxidative status explain variation in thermal acclimation capacity between individual zebrafish (Danio rerio)
1. Evolutionary theory predicts that the capacity to acclimate should be favoured in variable environments. However, perfect compensation for thermal variation is rare and the capacity for thermal acclimation can vary considerably between individuals within natural populations. This variation may be explained by costs associated with acclimation, but it is not clear what these costs are. 2. We tested the hypothesis that oxidative stress is a cost of acclimation that could explain the variation between individuals in acclimation capacity. We acclimated individual mosquitofish (Gambusia holbrooki, n = 416) to 18oC and 28oC sequentially, and determined swimming performance at each temperature to evaluate their acclimation capacity. Fish were then acclimated to either cold (18oC) or warm (28oC) conditions, and we increased antioxidant capacities of a subset of fish experimentally by administering N-acetyl cysteine (NAC). We measured H2O2 production, catalase antioxidant activities, and oxidative damage to proteins and membranes. 3. We show that there is significant variation in acclimation capacity between individuals, and that there is a trade-off between acclimation capacity and swimming performance in warm conditions. Mean swimming performance across both acclimation temperatures increased with increasing acclimation capacity, but the increase was small biologically. Hence, greater thermal plasticity (high acclimation capacity) resulted in only minor performance benefits across acclimation conditions. We verified this rather surprising result in replicate populations grown in outdoor mesocosms. 4. ROS production, antioxidant activities, and oxidative damage were higher in cold-acclimated fish, and particularly in those fish with low capacity for acclimation. However, experimentally increasing antioxidant capacities with NAC alleviated these changes to oxidative status, suggesting a causal relationship. Hence, oxidative stress may be a cost that constrains the capacity for acclimation. Together, the performance trade-off and oxidative cost indicate that phenotypic plasticity is not always advantageous in variable environments, and instead bet-hedging may be a more beneficial strategy, particularly in short-lived species.
Data from: Explaining global variation in the latitudinal diversity gradient: meta-analysis confirms known patterns and uncovers new ones
Aim: The pattern of increasing biological diversity from high latitudes to the equator [latitudinal diversity gradient (LDG)] has been recognized for > 200 years. Empirical studies have documented this pattern across many different organisms and locations. Our goal was to quantify the evidence for the global LDG and the associated spatial, taxonomic and environmental factors. We performed a meta-analysis on a large number of individual LDGs that have been published in the 14 years since Hillebrand's ground-breaking meta-analysis of the LDG, using meta-analysis and meta-regression approaches largely new to the fields of ecology and biogeography. Location: Global. Time period: January 2003–September 2015. Major taxa studied: Bacteria, protists, plants, fungi and animals. Methods: We synthesized the outcomes of 389 individual cases of LDGs from 199 papers published since 2003, using hierarchical mixed-effects meta-analysis and multiple meta-regression. Additionally, we re-analysed Hillebrand's original dataset using modern methods. Results: We confirmed the generality of the LDG, but found the pattern to be weaker than was found in Hillebrand's study. We identified previously unreported variation in LDG strength and slope across longitude, with evidence that the LDG is strongest in the Western Hemisphere. Locational characteristics, such as habitat and latitude range, contributed significantly to LDG strength, whereas organismal characteristics, including taxonomic group and trophic level, did not. Modern meta-analytical models that incorporate hierarchical structure led to more conservative and sometimes contrasting effect size estimates relative to Hillebrand's initial analysis, whereas meta-regression revealed underlying patterns in Hillebrand's dataset that were not apparent with a traditional analysis. Main conclusions: We present evidence of global latitudinal, longitudinal and habitat-based patterns in the LDG, which are apparent across both marine and terrestrial realms and over a broad taxonomic range of organisms, from bacteria to plants and vertebrates.
Geographic, seasonal and ontogenetic variations of δ15N and δ13C of Japanese sardine explained by baseline variations and diverse fish movements
<p><span>Understanding and predicting variability in the stable isotope ratios of nitrogen and carbon (δ15N and δ13C, respectively) of small pelagic fish is crucial to enable isotopic studies of a variety of marine predators that feed on them. However, because the isotope ratios reflect plastic feeding habits and fish migration in addition to baseline variation, their predictions require a mechanistic understanding of how each factor contributes. Here, we investigated the habitat-wide variability of δ<sup>15</sup>N and δ<sup>13</sup>C of the Japanese sardine <em>Sardinops melanostictus</em> in the western North Pacific and its marginal seas (the East China Sea and the Sea of Japan). By combining this with the archived particulate organic matter (POM) dataset as a baseline, we aimed to understand how ecological processes and baseline fluctuations affect isotope ratios of the sardine. Both δ<sup>15</sup>N and δ<sup>13</sup>C of sardine showed significant geographical and seasonal trends, with higher values in southern nearshore areas, including the Seto Inland Sea, intermediate values in marginal seas and lower values in Pacific offshore areas. As the variations were largely consistent with the geographic and temporally integrated seasonal trends of isotope ratios of POM, respectively, the baseline variations are the main determinant of sardine isotope composition. The trophic levels of sardine are therefore not significantly different between regions, with possible minor increases in the southern nearshore area. Adults showed less geographic variation than larvae and juveniles, likely due to slower turnover periods and wider migration ranges. Although larval and juvenile isotope ratios in marginal seas mostly reflected the local baseline, those in the Pacific offshore often reflected the baseline in the neighbouring southern region, suggesting contrasting juvenile movements between regions. Our results suggest that the δ<sup>15</sup>N and δ<sup>13</sup>C of Japanese sardine strongly reflect baseline variations, but can also be influenced by life-stage- and region-dependent fish movements, thereby demonstrating both the possibility and difficulty of mechanistically modelling the isoscapes of lower trophic level species.</span></p>
Data from: Environment but not geography explains genetic variation in the invasive and largely panmictic European starling in North America
Populations of invasive species that colonize and spread in novel environments may differentiate both through demographic processes and local selection throughout the genome. European starlings (Sturnus vulgaris) were introduced to New York in 1890 and subsequently spread throughout North America, becoming one of the most widespread and numerous bird species on the continent. Genome-wide comparisons across starling individuals and populations can identify demographic and/or selective factors that facilitated this rapid and successful expansion. We investigated patterns of genomic diversity and differentiation using reduced-representation genome sequencing (ddRADseq) of 17 starling populations. Consistent with this species' high dispersal rates and rapid expansion history, we found low genome-wide differentiation and few FST outliers even at a continental scale. Despite starting from a founding population of approximately 180 individuals, North American starlings do not seem to have undergone a detectable genetic bottleneck: they have maintained an extremely large effective population size since introduction. We find more than 200 variants that correlate with temperature and/or precipitation. Genotype-environment associations (but not outlier scans) identify these SNPs against a background of negligible genome- and range-wide divergence. Such variants fall in the coding regions of genes associated with metabolism, stress, and neurological function. This evidence for incipient local adaptation in North American starlings suggests that it can evolve rapidly even in wide-ranging and evolutionarily young populations. This survey of genomic signatures of expansion in North American starlings is the most comprehensive to date and complements ongoing studies of world-wide local adaptation in these highly dispersive and invasive birds.
Data from: Timbres of tolerance: Co-feeding tolerance in chimpanzees and bonobos is better explained by group-specific variation than species differences
<p><span>The human species exhibits a remarkable level of social tolerance which has propelled a plethora of behavioural expressions pivotal to our biological success. To date, the evolutionary origins of humans' "ultra-sociality" remain unclear, despite a substantial research focus on our closest living evolutionary relatives, the great apes. Bonobos are typically portrayed as more socially tolerant than chimpanzees and consequentially (sometimes) presented as a better model to study the evolutionary roots of human sociality. Yet, the current evidence supporting such a species-level categorization is equivocal. Here, we used validated group-level co-feeding tasks to test 16 independent <em>Pan </em>groups living in zoo (n=9) and sanctuary (n=7) settings, representing 225 individuals. We found that the expressions of social tolerance substantially overlapped between species, thus precluding categorical inference at the species level. Instead, marked differences were observed among groups, with some bonobo groups exhibiting higher social tolerance than chimpanzee groups, and vice versa. Interestingly, substantial intergroup variation was found within species living in the same environment, which attests to Pan's behavioural flexibility. We conclude that the pervasive dichotomy between the tolerant bonobo and the belligerent chimpanzee requires quantitative nuance, and that accurate phylogenetic tracing of (human) social behaviour necessitates estimations of intraspecific intergroup variation.</span></p>
High-resolution 3D forest structure explains ecomorphological trait variation in assemblages of saproxylic beetles
<p>Climate, topography, and the 3D structure of forests are major drivers affecting local species communities. However, little is known about how the specific functional traits of saproxylic (wood-living) beetles, involved in the recycling of wood, might be affected by those environmental characteristics.</p> <p>Here we combine ecological and morphological traits available for saproxylic beetles and airborne laser scanning (ALS) data in Bayesian trait-based joint species distribution models to study how traits drive the distributions of more than 230 species in temperate forests of Europe.</p> <p>We found that elevation (as a proxy for temperature and precipitation) and the proportion of conifers played important roles in species occurrences while variables related to habitat heterogeneity and forest complexity were less relevant. Further, we showed that local communities were shaped by environmental variation primarily through their ecological traits whereas morphological traits were involved only marginally. As predicted, ecological traits influenced species' responses to forest structure, and to other environmental variation, with canopy niche, wood decay niche, and host preference as the most important ecological traits. Conversely, no links between morphological traits and environmental characteristics were observed. Both models, however, revealed strong phylogenetic signal in species' response to environmental characteristics.</p> <p>These findings imply that alterations of climate and tree species composition have the potential to alter saproxylic beetle communities in temperate forests. Additionally, ecological traits help explain species' responses to environmental characteristics and thus should prove useful in predicting their responses to future change. It remains challenging, however, to link simple morphological traits to species' complex ecological niches.</p>
Data from: Among-species variation in six decades of changing migration timings explained through ecology, life-history and abundance
<p>Species utilising seasonal environments must now alter timings of key life-history events in response to large-scale climatic changes, thereby maintaining trophic synchronies. Yet substantial among-species variation in cross-decadal phenological changes is observed. Transitioning from basic description of such variation towards prediction of future phenological responses now requires standardised studies that rigorously quantify and explain variation in the direction, magnitude and form of changing timings across diverse species in relation to key ecological and life-history variables. Accordingly, we fitted multi-quantile regressions to 59 years of high-quality multi-species data on spring and autumn bird migration timings through northern Scotland. We demonstrate substantial variation in cross-decadal changes in timings among 72 species, and quantify the degree to which variation can be explained through differences in species ecology, life-history and population trajectories. Consistent with predictions, species with seasonal diets, narrower breeding habitat breadths, shorter generation lengths and capability to produce multiple offspring broods per year advanced their migration timing in one or both seasons. In contrast, species with less seasonal diets, and that produce single annual offspring broods, showed no change. Meanwhile, contrary to prediction, long-distance migrants advanced their migration timings as much as short-distance migrants. Changes in migration timing also varied with changes in local migratory abundance, such that species with increasing seasonal abundance apparently altered their migration timing, whilst species with decreasing abundance did not. These patterns concur with expectation if changing migration timing is adaptive. However, we demonstrate that similar patterns can be generated through numerical sampling processes given changing abundances, implying that apparent phenology-abundance relationships should be carefully validated and interpreted. Overall, our results show that migrant bird species with differing ecologies and life-histories have shown systematically differing phenological changes over six decades contextualised by large-scale environmental changes, potentially facilitating future predictions and altering temporal dynamics of seasonal species co-occurrences.</p>
Data from: Evolutionary variation in gene conversion at the avian MHC is explained by fluctuating selection, gene copy numbers, and life history
<p>The Major Histocompatibility Complex (MHC) multigene family encodes key pathogen-recognition molecules of the vertebrate adaptive immune system. Hyper-polymorphism of MHC genes is <em>de novo</em> generated by point mutations, but new haplotypes may also arise by re-shuffling of existing variation through intra- and inter-locus gene conversion. Although the occurrence of gene conversion at the MHC has been known for decades, we still have limited understanding of its functional importance. Here, I took advantage of extensive genetic resources (~9000 sequences) to investigate a broad scale macroevolutionary patterns in gene conversion processes at the MHC across nearly 200 avian species. Gene conversion was found to constitute a universal mechanism in birds, as 83% of species showed footprints of gene conversion at either MHC class and 25% of all allelic variants were attributed to gene conversion. Gene conversion processes were stronger at MHC-II than MHC-I, but inter-specific variation at both MHC classes was explained by similar evolutionary scenarios, reflecting fluctuating selection towards different optima and drift. Gene conversion showed uneven phylogenetic distribution across birds and was driven by gene copy number variation, supporting significant role of inter-locus gene conversion processes in the evolution of the avian MHC. Finally, MHC gene conversion was stronger in species with fast life histories (high fecundity) and in long-distance migrants, likely reflecting variation in population sizes and host-pathogen coevolutionary dynamics. The results provide a robust comparative framework for understanding macroevolutionary variation in gene conversion at the avian MHC and reinforce important contribution of this mechanism to functional MHC diversity.</p>
Size, connectivity and edge effects of stream habitats explain spatiotemporal variation in brown trout (Salmo trutta) density
<p>Ecological theory postulates that size and isolation of habitat patches impact the colonization/extinction dynamics that determine community species richness and population persistence. Given the key role of lotic habitats for life history completion in rheophilic fish, evaluating how the distribution of swift-flowing habitats affects the abundance and dynamics of subpopulations is essential. Using extensive electrofishing data, we show that merging island biogeography with meta-population theory, where lotic habitats are considered as islands in a lentic matrix, can explain spatiotemporal variation in occurrence and density of brown trout (Salmo trutta). Subpopulations in larger and less isolated habitat patches had higher average densities and smaller between-year density fluctuations. Larger habitat patches also had lower predicted risk of excessive zero catches, indicative of lower extinction risk. Trout density further increased with distance from the edge of adjacent lentic habitats with predator (Esox lucius) presence, suggesting that edge- and matrix-related mortality contributes to the observed patterns. These results can help reduce the negative impacts that habitat loss and fragmentation have on biodiversity, by stressing the importance of suitable habitat size and connectivity, and aid in prioritization of habitat restoration, dam removal and reintroduction programs aimed at vitalizing declining and locally extinct riverine fish populations.</p>
Data from: Explaining productivity variation in response to nitrogen addition and warming requires intraspecific variability
<p>1. Recent studies have shown that intraspecific trait variability is an important source of total trait variation. However, the contribution of intraspecific variability to ecosystem functions in the face of global change remains unknown.</p> <p>2. We measured plant height, leaf area, specific leaf area, leaf dry matter content and leaf thickness of 26 species at individual or leaf level and aboveground net primary productivity in 48 subplots subjected to 8 years of nitrogen addition and warming in a Tibetan alpine meadow. We split community weighted mean (CWM) and Rao's quadratic entropy (Rao) of individuals' traits within a given community into "fixed value" (only caused by interspecific difference of traits) and intraspecific variability (only caused by intraspecific difference), respectively, using a variance partitioning method.</p> <p>3. We found that productivity showed a humped back response to nitrogen addition: it was highest at intermediate levels of nitrogen fertilization. The response trend was mediated by the changes of plant functional structure. Productivity was positive with fixed Rao of plant height and intraspecific variability of leaf area, i.e. community having higher fixed variability of plant height and individuals producing bigger leaf area can increase productivity via niche complementary and dominance effect. Warming reduced productivity directly and marginally decreased individuals' leaf area which suppresses productivity indirectly.</p> <p>4. Our research suggests the non-negligible role of plant intraspecific trait variability in maintaining ecosystem functions, especially in the face of global change.</p>
Explaining variation in plant-herbivore associational effects in a tree biodiversity experiment
<p>Within biodiversity-ecosystem function research, a major outstanding question is how herbivory, a critical ecosystem function at the base of the food web, changes along gradients of plant biodiversity. Neighborhood-level associational effects are hypothesized to be a strong driver of biodiversity-herbivory relationships, but we lack a successful framework that explains the wide variation observed in the sign and magnitude of plant-herbivore associational effects, particularly in systems with mainly generalist herbivores. In this study, we combine measurements from a tree biodiversity field experiment with simulation to provide a framework for explaining variation in plant-herbivore associational effects, particularly when herbivores that feed on many different species (e.g., generalists) cause most damage. We show that monoculture herbivory levels of focal species and their neighbors predict the direction and strength of associational effects. We provide evidence that this may be due to a "spillover effect", in which some insect herbivores attracted to focal individuals ultimately end up feeding on neighboring individuals. With an empirically parameterized simulation, we explain how spatial organization modifies biodiversity-ecosystem function relationships when associational effects operate. We suggest a set of experiments to test the generality of our conceptual framework, to elucidate the underlying mechanisms that produce the patterns we find, and to ultimately increase the predictability of plant-herbivore associational effects. We conclude by discussing how our results might inform pest management in diversified agroecosystems and reforestation sites.</p> <p><em>Synthesis</em></p> <p>Our results provide a potential framework for explaining why positive and negative plant-herbivore associational effects are often balanced in systems with primarily generalist herbivores and point to a path forward for predicting when increased plant biodiversity will be associated with increased, decreased, or unchanged levels of insect herbivory on individual plant species in such systems.</p> <p class="MsoListParagraph"><span><span> </span></span></p>
Variation in the production of plant tissues bearing extrafloral nectaries explains temporal patterns of ant attendance in Amazonian understory plants
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Data from: Divergence of vessel diameter explains interspecific variation in hydraulic safety to salinity in the Sundarbans mangrove ecosystem
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Data and R code from: Global Phanerozoic biodiversity, can variation be explained by spatial sampling intensity
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Data from: Evolutionary variation in gene conversion at the avian MHC is explained by fluctuating selection, gene copy numbers, and life history
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Datasets - Evolutionary history, not ecogeographic rules, explains size variation of tropical insects along elevational gradients
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Genetic drift does not sufficiently explain patterns of electric signal variation among populations of the mormyrid electric fish Paramormyrops kingsleyae
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Data from: Among-species variation in six decades of changing migration timings explained through ecology, life-history and abundance
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ScienceDex guides
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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.