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560 results for “Direct effects”
The direct and indirect effects of environmental toxicants on the health of bumble bees and their microbiomes
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Data from: Sex-specific selection on plant architecture through 'budget' and 'direct' effects in experimental populations of a wind-pollinated herb
Sexual selection may contribute to the evolution of plant sexual dimorphism by favoring architecture traits that improve pollen dispersal to mates in males. In both sexes, larger individuals may be favored if large size allows the allocation of more resources to gamete production (a 'budget' effect of size). In wind-pollinated plants, large size may also benefit males if it allows them to liberate pollen from greater heights, fostering its dispersal (a 'direct' effect of size). To assess these effects and their implications for trait selection, we measured selection gradients on plant morphology in both males and females, as well as pollen production and dispersal in males, of the wind-pollinated dioecious herb Mercurialis annua. In two separate experimental common gardens established at different densities, selection strongly favored plants dispersing their pollen further. Selection for pollen production was observed in the high-density garden only and was weak. In addition, male morphologies associated with increased mean pollen dispersal differed between the two gardens as elongated branches were favored in the high-density garden while shorter plants with longer peduncles bearing inflorescences were advantaged the low-density garden. Larger females were selected in both gardens. Our results point to the importance of selection on male traits that affect pollen dispersal, and to a lesser extent pollen production.
Data from: Direct and indirect causal effects of heterozygosity on fitness-related traits in Alpine ibex
Heterozygosity–fitness correlations (HFCs) are a useful tool to investigate the effects of inbreeding in wild populations, but are not informative in distinguishing between direct and indirect effects of heterozygosity on fitness-related traits. We tested HFCs in male Alpine ibex (Capra ibex) in a free-ranging population (which suffered a severe bottleneck at the end of the eighteenth century) and used confirmatory path analysis to disentangle the causal relationships between heterozygosity and fitness-related traits. We tested HFCs in 149 male individuals born between 1985 and 2009. We found that standardized multi-locus heterozygosity (MLH), calculated from 37 microsatellite loci, was related to body mass and horn growth, which are known to be important fitness-related traits, and to faecal egg counts (FECs) of nematode eggs, a proxy of parasite resistance. Then, using confirmatory path analysis, we were able to show that the effect of MLH on horn growth was not direct but mediated by body mass and FEC. HFCs do not necessarily imply direct genetic effects on fitness-related traits, which instead can be mediated by other traits in complex and unexpected ways.
Data from: Immunoglobulin detection in wild birds: effectiveness of three secondary anti-avian IgY antibodies in direct ELISAs in 41 avian species
1.Immunological reagents for wild, non-model species are limited or often non-existent for many species. 2. In this study, we compare the reactivity of a new anti-passerine IgY secondary antibody with existing secondary antibodies developed for use with birds. Samples from 41 species from the following six avian orders were analysed: Anseriformes (1 family, 1 species), Columbiformes (1 family, 2 species), Galliformes (1 family, 1 species), Passeriformes (16 families, 34 species), Piciformes (1 family, 2 species) and Suliformes (1 family, 1 species). Direct ELISAs were performed to detect total IgY using goat anti-passerine IgY, goat anti-chicken IgY or goat anti-bird IgY secondary antibodies. 3.The anti-passerine antibody exhibited significantly higher IgY reactivity compared to the anti-chicken and/or anti-bird antibodies in 80% of the passerine families tested. Birds in the order Piciformes (woodpeckers) and order Suliformes (cormorants) were poorly detected by all three secondary antibodies. A comparison of serum and plasma IgY levels was made within the same individuals for two passerine species (house finch and white-crowned sparrow), and serum exhibited significantly more IgY than the plasma for all three secondary antibodies. This result indicates that serum may be preferred to plasma when measuring total antibody levels in blood. 4.This study indicates that the anti-passerine IgY secondary antibody can effectively be used in immunological assays to detect passerine IgY for species in most passerine families and is preferred over anti-chicken and anti-bird secondary antibodies for the majority of passerine species. This anti-passerine antibody will allow for more accurate detection and quantification of IgY in more wild bird species than was possible with previously available secondary antibodies.
Data from: Direct and indirect effects of nitrogen enrichment on soil organisms and carbon and nitrogen mineralization in a semi‐arid grassland
1. Semi-arid grasslands on the Mongolian Plateau are expected to experience high inputs of anthropogenic reactive nitrogen in this century. It remains unclear, however, how soil organisms and nutrient cycling are directly affected by N enrichment (i.e., without mediation by plant input to soil) vs. indirectly affected via changes in plant-related inputs to soils resulting from N enrichment. 2. To test the direct and indirect effects of N enrichment on soil organisms (bacteria, fungi, and nematodes) and their associated C and N mineralization, in 2010 we designated two subplots (with plants and without plants) in every plot of a six-level N-enrichment experiment established in 1999 in a semi-arid grassland. 3. In 2014, 4 years after subplots with and without plant were established, N enrichment had substantially altered the soil bacterial, fungal, and nematode community structures due to declines in biomass or abundance whether plants had been removed or not. N enrichment also reduced the diversity of these groups (except for fungi) and the soil C mineralization rate and induced a hump-shaped response of soil N mineralization. As expected, plant removal decreased the biomass or abundance of soil organisms and C and N mineralization rates due to declines in soil substrates or food resources. 4. Analyses of plant removal-induced changes (ratios of without- to with-plant subplots) showed that microorganisms and C and N mineralization rates were not enhanced as N enrichment increased but that nematodes were enhanced as N enrichment increased, indicating that the effects of plant removal on soil organisms and mineralization depended on trophic level and nutrient status.5. Surprisingly, there was no statistical interaction between N enrichment and plant removal for most variables, indicating that plant-related inputs did not qualitatively change the effects of N enrichment on soil organisms or mineralization. Structural equation modeling confirmed that changes in soil communities and mineralization rates were more affected by the direct effects of N enrichment (via soil acidification and increased N availability) than by plant-related indirect effects. Our results provide insight into how future changes in N-deposition and vegetation may modify below-ground communities and processes in grassland ecosystems.
Data from: Direct and indirect genetic and fine-scale location effects on breeding date in song sparrows
Quantifying direct and indirect genetic effects of interacting females and males on variation in jointly expressed life-history traits is central to predicting microevolutionary dynamics. However, accurately estimating sex-specific additive genetic variances in such traits remains difficult in wild populations, especially if related individuals inhabit similar fine-scale environments. Breeding date is a key life-history trait that responds to environmental phenology and mediates individual and population responses to environmental change. However, no studies have estimated female (direct) and male (indirect) additive genetic and inbreeding effects on breeding date, and estimated the cross-sex genetic correlation, while simultaneously accounting for fine-scale environmental effects of breeding locations, impeding prediction of microevolutionary dynamics. We fitted animal models to 38 years of song sparrow (Melospiza melodia) phenology and pedigree data to estimate sex-specific additive genetic variances in breeding date, and the cross-sex genetic correlation, thereby estimating the total additive genetic variance while simultaneously estimating sex-specific inbreeding depression. We further fitted three forms of spatial animal model to explicitly estimate variance in breeding date attributable to breeding location, overlap among breeding locations and spatial autocorrelation. We thereby quantified fine-scale location variances in breeding date and quantified the degree to which estimating such variances affected the estimated additive genetic variances. The non-spatial animal model estimated nonzero female and male additive genetic variances in breeding date (sex-specific heritabilities: 0·07 and 0·02, respectively) and a strong, positive cross-sex genetic correlation (0·99), creating substantial total additive genetic variance (0·18). Breeding date varied with female, but not male inbreeding coefficient, revealing direct, but not indirect, inbreeding depression. All three spatial animal models estimated small location variance in breeding date, but because relatedness and breeding location were virtually uncorrelated, modelling location variance did not alter the estimated additive genetic variances. Our results show that sex-specific additive genetic effects on breeding date can be strongly positively correlated, which would affect any predicted rates of microevolutionary change in response to sexually antagonistic or congruent selection. Further, we show that inbreeding effects on breeding date can also be sex specific and that genetic effects can exceed phenotypic variation stemming from fine-scale location-based variation within a wild population.
Data from: The direct effects of male-killer infection on fitness of ladybird hosts (Coleoptera: Coccinellidae)
Male-killing bacteria are common in insects, and are thought to persist in host populations primarily by indirect fitness benefits to infected females, while direct fitness effects are generally assumed to be neutral or deleterious. Here, we estimated the effect of male-killer infection on direct fitness (number of eggs laid, as a measure of fecundity, together with survival) and other life-history traits (development time and body size) in seven ladybird host/male-killer combinations. Effects of male-killers on fecundity ranged, as expected, from costly to neutral, however we found evidence of reduced development time and increased survival and body size, in infected strains. Greater body size in Spiroplasma-infected Harmonia axyridis corresponded to greater ovariole number, and therefore higher potential fecundity. To our knowledge, this is the first report of direct benefits of male-killer infection after explicitly controlling for indirect fitness effects. Neutral or deleterious fitness effects of male-killer infection should not therefore be automatically assumed.
Data from: Direct and indirect ecosystem effects of evolutionary adaptation in the Trinidadian guppy (Poecilia reticulata)
Ecological and evolutionary processes may interact on the same timescale, but we are just beginning to understand how. Several studies have examined the net effects of adaptive evolution on ecosystem properties. However, we do not know if the these effects are confined to direct interactions or if they propagate further through indirect ecological pathways. Even less well understood is how the combination of direct and indirect ecological effects of the phenotype promotes or inhibits evolutionary change. We coupled mesocosm experiments and ecosystem modeling to evaluate the ecological effects of local adaptation in Trinidadian guppies (Poecilia reticulata). The experiments show that guppies adapted to life with and without predators alter the ecosystem directly through differences in diet. The ecosystem model reveals that the small total indirect effect of the phenotype observed in the experiments is likely a combination of several large indirect effects which act in opposing directions. The model further suggests that these indirect effects can reverse the direction of selection that direct effects alone exert back on phenotypic variation. We conclude that phenotypic divergence can have major effects deep in the web of indirect ecological interactions and even small total indirect effects can radically change the dynamics of adaptation.
Data from: Direct and indirect effects of early-life environment on lifetime fitness of bighorn ewes
Cohort effects, when a common environment affects long-term performance, can have a major impact on population dynamics. Very few studies of wild animals have obtained the necessary data to study the mechanisms leading to cohort effects. We exploited 42 years of individual-based data on bighorn sheep to test for causal links between birth density, body mass, age at first reproduction, longevity, and lifetime reproductive success using path analysis. Specifically, we investigated whether the effect of early-life environment on lifetime fitness was the result of indirect effects through body mass or direct effects of early-life environment on fitness. Additionally, we evaluated whether the effects of early-life environment where dependant on the environment experienced during adulthood. Contrary to expectation, the effect on lifetime reproductive success mediated through body mass was weak compared to the effects found via a delay in age at first reproduction, reduced longevity, and the direct effect of birth density. Birth density also had an important indirect effect on lifetime reproductive success through reduced longevity, but only when adult density was high. Our results show that the potential long-term consequences of a harsh early-life environment on fitness are likely to be underestimated if investigations are limited to body mass instead of fitness at several life stages, or if the interactions between past and present environment is ignored.
Data from: Quantifying direct vs. indirect effects of nectar robbers on male and female components of plant fitness
1. Plants interact simultaneously with both mutualists and antagonists. While webs of plant-animal interactions in natural systems can be highly complex, most interactions can be simplified into those that are either direct (mediated through pairwise interactions) or indirect (mediated through third-party species). Mechanistic studies of the direct and indirect pathways by which foliar herbivores affect plants have been well explored; however, mechanistic explorations of how floral herbivores, such as nectar robbers, affect total plant fitness via direct vs. indirect pathways have received less attention. 2. The goal of this study was to assess the importance of direct vs. pollinator-mediated indirect effects of a floral antagonist on female and male components of plant fitness. We focused on the hummingbird-pollinated plant scarlet gilia, Ipomopsis aggregata, which is nectar-robbed by the bumble bee Bombus occidentalis. Prior studies have found evidence for pollinator-mediated indirect effects of robbing on female and male components of I. aggregata fitness, but the mechanisms by which these indirect effects occur, and experimental evidence supporting or refuting direct effects of robbing, have been lacking. 3. We found no evidence for direct effects of robbing on plant fitness. Robbers did not act as pollinators of I. aggregata nor did they directly affect seed production by making nectar-robber holes or removing nectar in hand-pollinated flowers. Moreover, robbing had no direct effect on pollen production per flower or the ability of pollen from robbed flowers to sire seeds in hand-pollinations. 4. However, nectar robbing had indirect effects on plant reproduction mediated through per-visit pollinator effectiveness at depositing pollen in robbed vs. unrobbed flowers. A simple model of a plant-robber-pollinator system suggested that robbing effects in general may occur through more indirect mechanisms when nectar removal by robbers is high relative to nectar replenishment, and that compensation for robbing is then more profitable through the production of additional flowers. 5. Synthesis. Our results highlight the importance of indirect effects in mediating the fitness consequences of species interactions.
Data from: Direct effects dominate responses to climate perturbations in grassland plant communities
Theory predicts that strong indirect effects of environmental change will impact communities when niche differences between competitors are small and variation in the direct effects experienced by competitors is large, but empirical tests are lacking. Here we estimate negative frequency dependence, a proxy for niche differences, and quantify the direct and indirect effects of climate change on each species. Consistent with theory, in four of five communities indirect effects are strongest for species showing weak negative frequency dependence. Indirect effects are also stronger in communities where there is greater variation in direct effects. Overall responses to climate perturbations are driven primarily by direct effects, suggesting that single species models may be adequate for forecasting the impacts of climate change in these communities.
Data from: Direct and indirect effects of pine silviculture on the larval occupancy and breeding of declining amphibian species
1. Plantation silviculture is increasing globally and is particularly intensive in temperate coniferous forests, where densely planting trees requires practices common to non-conifer systems that can alter forest floor microhabitat, and potentially threaten amphibian persistence. Most declining amphibian species depend on specific forest microhabitats as terrestrial refugia, but amphibian extirpation associated with tree harvest alone appears unlikely, suggesting that impacts of planting forests on groundcover might better predict recent declines in amphibian occupancy. 2. We repeatedly sampled larval presence or absence of 10 amphibian species native to temperate coniferous forest in the Southeastern United States for one year at 62 isolated wetlands located in either naturally regenerating or planted forest (plantation) to assess three direct ways that planted forests might reduce amphibian breeding site occupancy by: 1) increasing conifer densities, 2) decreasing groundcover, and 3) an indirect pathway, whereby increased tree densities at plantations might reduce groundcover and thus amphibian site occupancy. 3. After controlling for wetland traits and accounting for differences in detection, breeding site occupancy for 8/10 amphibian species was dependent upon whether forests were planted surrounding wetlands (within 300 m). Herbaceous groundcover, not canopy, most commonly influenced occupancy and increased occupancy for declining surface active or fossorial amphibians. 4. Path analyses showed that, by directly and indirectly reducing groundcover (via conifer densities), plantations had significantly lower occupancy of two declining surface active or fossorial frog species, whereas two common aquatic frog species were tolerant to planting conifers. Among declining species, salamanders showed a greater reduction in occupancy than anurans, likely because of greater vulnerability to the drier forest floor conditions of plantation than naturally regenerating forests. 5. Synthesis and applications: Direct negative impacts of coniferous plantation on amphibians can be addressed by limiting groundcover and soil impacts, including switching from high intensity practices, such as mechanical chopping vegetation or bedding soil, to lower intensity site preparation treatments that are less likely to significantly disturb groundcover. Indirect negative effects of dense canopy cover at planted forests could be lowered by periodically thinning canopies prior to final harvest, thus increasing intact forest groundcover and the conservation of both common and declining amphibians.
Data from: Grazers affect selection on inflorescence height both directly and indirectly and effects change over time
Selection mediated by one biotic agent will often be modified by the presence of other biotic interactions, and the importance of such indirect effects might change over time. We conducted an 11-year field experiment to test the prediction that large grazers affect selection on floral display of the dimorphic herb Primula farinosa not only directly through differential grazing damage, but also indirectly by affecting vegetation height and thereby selection mediated by pollinators and seed predators. Exclusion of large grazers increased vegetation height and the strength of pollinator-mediated selection for tall inflorescences and seed predator-mediated selection for short inflorescences. The direct effect of grazers on selection resulting from differential grazing damage to the two scape morphs showed no temporal trend. By contrast, the increase in vegetation height in exclosures over time was associated with an increase in selection mediated by pollinators and seed predators. In the early years of the experiment, the indirect effects of grazers on selection mediated by pollinators and seed predators were weak, whereas at the end of the experiment, the indirect effects were of similar magnitude as the direct effect due to differential grazing damage. The results demonstrate that the indirect effects of a selective agent can be as strong as its direct effects, and that the relative importance of direct vs. indirect effects on selection can change over time. A full understanding of the ecological processes governing variation in selection thus requires that both direct and indirect effects of biotic interactions are assessed.
Data from: Comparison of infinitesimal and finite locus models for long-term breeding simulations with direct and maternal effects at the example of honeybees
Stochastic simulation studies of animal breeding have mostly relied on either the infinitesimal genetic model or finite polygenic models. In this study, we investigated the long-term effects of the chosen model on honeybee breeding schemes. We implemented the infinitesimal model, as well as finite locus models, with 200 and 400 gene loci and simulated populations of 300 and 1000 colonies per year over the course of 100 years. The selection was of a directly and maternally influenced trait with maternal heritability of h²_m = 0.42, direct heritability of h² d = 0.27, and a negative correlation between the effects of r_md = −0.18. Another set of simulations was run with parameters h²_m = 0.53, h²_d = 0.34, and r_md = −0.53. All models showed similar behavior for the first 20 years. Throughout the study, we observed a higher genetic gain in the direct than in the maternal effects and a smaller gain with a stronger negative covariance. In thelong-term, however, only the infinitesimal model predicted sustainable linear genetic progress, while the finite locus models showed sublinear behavior and, after 100 years, only reached between 58% and 62% of the mean breeding values in the infinitesimal model. While the infinitesimal model suggested a reduction of genetic variance by 33% to 49% after 100 years, the finite locus models saw a more drastic loss of 76% to 92%. When designing sustainable breeding strategies, one should, therefore, not blindly trust the infinitesimal model as the predictions may be overly optimistic. Instead, the more conservative choice of the finite locus model should be favored.
Data from: Behavior and nutritional condition buffer a large-bodied endotherm against direct and indirect effects of climate
Temporal changes in net energy balance of animals strongly influence fitness; consequently, natural selection should favor behaviors that increase net energy balance by buffering individuals against negative effects of environmental variation. The relative importance of behavioral responses to climate-induced variation in costs versus supplies of energy, however, is uncertain, as is the degree to which such responses are mediated by current stores of energy. We evaluated relationships among behavior, nutritional condition (i.e., energetic state), and spatiotemporal variation in costs versus supplies of energy available to a large-bodied endotherm, the North American elk (Cervus elaphus), occupying two ecosystems with contrasting climates; 1) a temperate, montane forest; and 2) an arid, high-elevation desert. We hypothesized that during spring through autumn, behavioral responses to the energetic landscape would be both context-dependent (i.e., would vary as a function of the environmental conditions experienced by elk in the forest versus the desert), and state-dependent (i.e., would vary as a function of the energetic state of an individual). We tested several predictions derived from that hypothesis by combining output from a biophysical model of the thermal environment with data on forage quality, animal locations, and nutritional condition of individuals. At the population level, elk in the desert selected areas that reduced costs of thermoregulation over those that provided the highest quality forage. In the forest, however, costs imposed by the thermal environment were less pronounced, and elk selected areas that increased access to high quality forage over those that reduced costs of thermoregulation. At the individual level, nutritional condition did not influence strength of selection for low-cost areas or high quality forage among elk in the forest. In the desert, however, strength of selection for low-cost areas (but not forage quality) was state-dependent - individuals in the poorest condition at the end of winter showed the strongest selection for areas that reduced costs of thermoregulation during spring and summer, and also expended the least amount of energy on locomotion. Our results highlight the importance of understanding the roles of behavior and nutritional condition in buffering endotherms against direct and indirect effects of climate on fitness.
Disentangling the direct and indirect effects of canopy and understory vegetation on the foraging habitat selection of the brown bear Ursus arctos
<p>Elucidating the factors affecting the foraging habitat selection of wildlife can further our understanding of the animal– habitat relationships and inform wildlife conservation and management. Canopy and understory vegetation may directly or indirectly affect the foraging habitat selection of carnivores through changes in habitat structure and prey availability, respectively; however, the relative importance of these two effects remains largely unknown. Dwarf bamboo Sasa kurilensis is a predominant understory plant that suppresses regeneration in the forests of northern Japan. The purpose of this study was to disentangle the direct and indirect effects of canopy forest type Larix kaempferi plantation versus natural mixed forest) and dwarf bamboo on foraging habitat selection of a large carnivore, the brown bear Ursus arctos. In the Shiretoko World Heritage, brown bears dig for cicada nymphs during summer. We evaluated the frequency of brown bear foraging on cicadas by investigating traces of digging for cicada nymphs. A structural equation model was used to statistically disentangle the direct and indirect effects of vegetation. Our results demonstrated that canopy and understory vegetation directly and indirectly affected foraging habitat selection of brown bears. Dwarf bamboo negatively affected cicada nymph density, which positively affected brown bear digging. This suggests that dwarf bamboo also had indirect negative effects on brown bears. Forest type had significant direct and indirect effects via change in cicada nymph density on foraging behavior in brown bears. Forestry managers in northern Japan, including the study site, try to remove dwarf bamboo for assisting natural regeneration. Removal of dwarf bamboo by scarification might not only promote natural regeneration, but also provide a beneficial foraging habitat for bears.</p>
Effect of Transcranial Direct Current Stimulation Associated With Aerobic Exercise Training for Patients With Fibromyalgia
ClinicalTrials.gov study NCT02358902. IPD Sharing: Not stated. Countries: 0. Publications: 1.
Effect of Transcranial Direct Current Stimulation on Peripheral Neuropathy
ClinicalTrials.gov study NCT03073759. IPD Sharing: NO. Countries: 1. Publications: 0.
Effect of Modeling Resin on Anterior Direct Composite Veneer
ClinicalTrials.gov study NCT06485024. IPD Sharing: Not stated. Countries: 0. Publications: 16.
Effects of Transcranial Direct Current Stimulation (tDCS) on Neuropathic Symptoms Following Burn Injury
ClinicalTrials.gov study NCT01795079. IPD Sharing: Not stated. Countries: 1. Publications: 0.
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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.