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Data from: Causes and consequences of repeatability, flexibility and individual fine-tuning of migratory timing in pike
1. Many organisms undertake migrations between foraging and breeding habitats and while it is assumed that reproductive timing affects fitness, little is known about the degree of individual consistency, and about the causes and consequences of individual variation in migratory timing in organisms other than birds. 2. Here, we report on a 6-year mark–recapture study, including 2048 individuals, of breeding migration in anadromous pike (Esox lucius), an iteroparous top-predatory fish that displays homing behaviour. By repeated sampling across years at a breeding site, we first quantify individual variation both within and between breeding events and then investigate phenotypic correlates and fitness consequences of arrival timing to the breeding site. 3. Our data demonstrate that males arrive before females, that large males arrive later than small males, that the timing of breeding migration varies among years and that individuals are consistent in their timing across years relative to other individuals in the population. 4. Furthermore, data on return rates indicate that arrival time is under stabilizing viability selection, and that individuals who are more flexible in their timing of arrival during the first reproductive years survive longer compared with less flexible individuals. Finally, longitudinal data demonstrate that individuals consistently fine-tune their arrival timing across years, showing that the timing of arrival to breeding sites is influenced by experience. 5. These findings represent rare evidence of how between- and within-individual variations in migratory timing across breeding events are correlated with phenotypic and fitness traits in an ecologically important keystone species. Our results emphasize the importance of considering variation in migratory timing both between and within individuals in studies investigating the fitness consequences of migratory behaviour and have implications for future management.
Data from: The presence of bacterial microcolonies on the maxillary sinus ciliary epithelium in healthy young individuals
Objective: The aim of this cross-sectional in vitro study was to evaluate the mucosal surfaces of healthy maxillary sinuses, explore different forms of bacterial microorganism colonies present on the mucous membrane, and determine a mucosal surface area they occupy. Methods: Samples of the maxillary sinus mucosa were collected from 30 healthy patients (M=11; F=19). The material was obtained during the Le Fort I osteotomy performed during corrective jaw surgery. The morphological and morphometric analysis of sinus mucosa and bacterial film that was grown on it was performed using scanning electron microscopy (SEM) as well as imaging software. Results: Scanning electron microscopy analysis showed the presence of different bacterium and bacteria-like structures in all the analyzed samples. In most cases, the bacterial film was mostly composed of diplococci-like and streptococci-like structures on the mucosa of the paranasal sinus. In any case, the mucous layer did not cover the whole lining of the evaluated sample. Each colony consists of more than 20 single bacterial cells, which has grown in aggregates. Conclusions: Under the conditions of normal homeostasis of the body, the maxillary sinuses present diverse bacterial colonization. The bacteria are dispersed or concentrated in single microcolonies of the biofilm on the border of the mucous covering the ciliary epithelium. There is no uniform layer of the biofilm covering the mucosa of the maxillary sinuses. Because the biofilm is detected on healthy individuals sinus mucosa, the clinical question if it may become pathogenic is unclear and require an explanation.
Data from: Assessing the expected response to genomic selection of individuals and families in Eucalyptus breeding with an additive-dominant model
We report a genomic selection (GS) study of growth and wood quality traits in an outbred F2 hybrid Eucalyptus population (n=768) using high-density single-nucleotide polymorphism (SNP) genotyping. Going beyond previous reports in forest trees, models were developed for different selection targets, namely, families, individuals within families and individuals across the entire population using a genomic model including dominance. To provide a more breeder-intelligible assessment of the performance of GS we calculated the expected response as the percentage gain over the population average expected genetic value (EGV) for different proportions of genomically selected individuals, using a rigorous cross-validation (CV) scheme that removed relatedness between training and validation sets. Predictive abilities (PAs) were 0.40–0.57 for individual selection and 0.56–0.75 for family selection. PAs under an additive+dominance model improved predictions by 5 to 14% for growth depending on the selection target, but no improvement was seen for wood traits. The good performance of GS with no relatedness in CV suggested that our average SNP density (~25 kb) captured some short-range linkage disequilibrium. Truncation GS successfully selected individuals with an average EGV significantly higher than the population average. Response to GS on a per year basis was ~100% more efficient than by phenotypic selection and more so with higher selection intensities. These results contribute further experimental data supporting the positive prospects of GS in forest trees. Because generation times are long, traits are complex and costs of DNA genotyping are plummeting, genomic prediction has good perspectives of adoption in tree breeding practice.
Data from: Effective number of breeders provides a link between interannual variation in stream flow and individual reproductive contribution in a stream salmonid
The effective number of breeders that give rise to a cohort (Nb) is a promising metric for genetic monitoring of species with overlapping generations; however, more work is needed to understand factors that contribute to variation in this measure in natural populations. We tested hypotheses related to interannual variation in Nb in two long-term studies of brook trout populations. We found no supporting evidence for our initial hypothesis that inline image reflects inline image (defined as the number of adults in a population at the time of reproduction). inline image was stable relative to inline image and did not follow trends in abundance (one stream negative, the other positive). We used stream flow estimates to test the alternative hypothesis that environmental factors constrain Nb. We observed an intermediate optimum autumn stream flow for both inline image (R2 = 0.73, P = 0.02) and full-sibling family evenness (R2 = 0.77, P = 0.01) in one population and a negative correlation between autumn stream flow and full-sib family evenness in the other population (r = −0.95, P = 0.02). Evidence for greater reproductive skew at the lowest and highest autumn flow was consistent with suboptimal conditions at flow extremes. A series of additional tests provided no supporting evidence for a related hypothesis that density-dependent reproductive success was responsible for the lack of relationship between Nb and NC (so-called genetic compensation). This work provides evidence that Nb is a useful metric of population-specific individual reproductive contribution for genetic monitoring across populations and the link we provide between stream flow and Nb could be used to help predict population resilience to environmental change.
Data from: Reduced sexual dichromatism, mutual ornamentation, and individual quality in the monogamous Zenaida dove, Zenaida aurita
Although variation in plumage coloration is known to occur both between and within sexes, its study remains limited to a few bird families. The Zenaida dove, Zenaida aurita, is a socially monogamous tropical columbid bird species, characterized by an overall cinnamon-brownish plumage and structural colorations on the head and neck. The species has been described as sexually dichromatic for plumage, although color differences between males and females are not obvious in the field. We investigated variation in the presumably melanin-based color of the crown, mantle, breast, and belly, in the iridescent dark-blue streaks on the head, and in the symmetric iridescent patches on the neck, over the whole spectrum visible to birds. Further, unlike most previous studies, we assessed covariation between plumage color and phenotypic traits in both males and females in relation to the putative signaling function of ornaments. Zenaida doves appeared to be slightly sexually dichromatic for the hue of pigment-based colored areas, with males being on average more reddish than females. However, this difference was not discernible when considering the avian visual system. Conversely, although the reflectance spectra of iridescent plumage did not significantly differ between sexes in brightness, chroma or spectral position of the peaks, color discrimination analyses showed that individuals should be able to perceive between- or within-sex differences in the color of the iridescent patch. In addition, several color parameters of brown and iridescent feathers were significantly related to territorial status, body condition, wing chord, and, albeit weakly, to individual multilocus heterozygosity. Overall, our results thus suggest that plumage color might be a reliable signal of quality in individuals of both sexes in this species. Further studies are needed to test the potential implication of plumage coloration in mate choice and mating patterns in the Zenaida Dove.
Data from: Functional genotypes are associated with commensal Escherichia coli strain abundance within host individuals and populations
The selective pressures that determine genotype abundance and distribution frequently vary between ecological levels. Thus, it is often unclear whether the same functional genotypes will become abundant at different levels and how selection acting at these different scales are linked. In this study, we examined whether particular functional genotypes, defined by the presence or absence of 34 genes, of commensal E. coli strains were associated with within-host abundance and/or host population abundance in a wild population of 54 adult mountain brushtail possums (Trichosurus cunninghami). Our results revealed that there was a positive correlation between a strain's relative abundance within individuals and the strain's abundance in the host population. We also found that strain abundance at both ecological levels was predicted by the same group of functional genes (agn43, focH, micH47, iroN, ygiL, ompT, kspmT2 and K1) that had associated patterns of occurrence. We propose that direct selection on the same functional genes at both levels may in part be responsible for the observed correlation between the ecological levels. However, a potential link between abundance within the host and excretion rate may also contribute.
Data from: Individual chambers for controlling crosses in wind pollinated plants
Controlled plant crosses can be an important component of studies ranging from applied artificial selection research to evolutionary investigations of heritability. Controlling pollen flow is especially challenging for wind-pollinated species. We developed a system capable of housing hundreds of ragweed (Ambrosia artemisiifolia) plants simultaneously in individual chambers through the reproductive portion of their lifecycles. We confirmed that our chambers allowed us to control pollen movement and paternity of offspring using unpollinated isolated plants and microsatellite markers for parents and their putative offspring. Our system had per plant costs and efficacy superior to pollen bags used in past studies for wind pollinated plants. Our chamber system is flexible, affordable, and widely applicable to other wind pollinated plants, or applications in which the distribution of highly mobile species, individuals, spores, or gametes must be controlled.
Individual variation creates diverse migratory portfolios in native populations of a mountain ungulate
<p>Ecological theory and empirical studies have demonstrated population-level demographic benefits resulting from a diversity of migratory behaviors with important implications for ecology, conservation, and evolution of migratory organisms. <a name="_Hlk29072366">Nevertheless, evaluation of migratory portfolios </a><a name="_Hlk29072297">(i.e., the variation in migratory behaviors across space and time among individuals within populations) </a>has received relatively little attention in migratory ungulates, where research has focused largely on the dichotomous behaviors (e.g., resident and migrant) of partially migratory populations. Using GPS data from 362 female bighorn sheep (<i>Ovis canadensis</i>) across 17 (restored = 4, augmented = 6, native = 7) populations in Montana and Wyoming, USA, we: 1) characterized migratory portfolios based on behavioral and spatial migratory characteristics, and 2) evaluated the relative influence of landscape attributes and management histories on migratory diversity. Native populations, which had been extant on the landscape for many generations, had more diverse migratory portfolios, higher behavioral switching rates, reduced seasonal range fidelity, and broad dispersion of individuals across summer and winter ranges. In contrast, restored populations with an abbreviated history on the landscape were largely non-migratory with a narrow portfolio of migratory behaviors, less behavioral switching, higher fidelity to seasonal ranges, and less dispersion on summer and winter ranges. Augmented populations were more variable and contained characteristics of both native and restored populations. Differences in migratory diversity among populations were associated with management histories (e.g., restored, augmented, or native). Landscape characteristics such as the duration and regularity of green-up, human landscape alterations, topography, and snow gradients were not strongly associated with migratory diversity. We suggest a two-pronged approach to restoring migratory portfolios in ungulates that first develops behavior-specific habitat models and then places individuals with known migratory behaviors into unoccupied areas in an effort to bolster migratory portfolios in restored populations, potentially with synergistic benefits associated with variation among individuals and resulting portfolio effects. Management efforts to restore diverse migratory portfolios may increase the abundance, resilience, and long-term viability of ungulate populations.</p>
Data from: Octopamine increases individual and collective foraging in a neotropical stingless bee
<p>The biogenic amine octopamine is a key modulator of individual and social behaviours in honeybees, but its role in the other group of highly eusocial bees, the stingless bees, remains largely unknown. In honeybees, octopamine mediates reward perception and affects a wide range of reward-seeking behaviours. Thus, we tested the hypothesis that octopamine increases individual foraging effort and collective food source exploitation in the neotropical stingless bee Plebeia droryana. Octopamine treatment caused a significant increase in the number of bees at artificial sucrose feeders and a 1.73-times higher individual foraging frequency. This effect can be explained by octopamine lowering the sucrose response threshold and, thus, increasing the perceived value of the food source. Our results demonstrate that, similar to its effects on honeybees, octopamine increases both individual and collective food source exploitation in P. droryana. This suggests that, despite having evolved many complex behaviours independently, OA might have similar regulatory effects on foraging behaviours in the two groups of highly eusocial bees.</p>
Data from: Linkage into care among newly diagnosed HIV-positive individuals tested through outreach and facility-based HIV testing models in Mbeya, Tanzania: a prospective mixed-method cohort study
Objective: Linkage to care is the bridge between HIV testing and HIV treatment, care and support. In Tanzania, mobile testing aims to address historically low testing rates. Linkage to care was reported at 14% in 2009 and 28% in 2014. The study compares linkage to care of HIV-positive individuals tested at mobile/outreach versus public health facility-based services within the first 6 months of HIV diagnosis. Setting: Rural communities in four districts of Mbeya Region, Tanzania. Participants: A total of 1012 newly diagnosed HIV-positive adults from 16 testing facilities were enrolled into a two-armed cohort and followed for 6 months between August 2014 and July 2015. 840 (83%) participants completed the study. Main outcome: measures We compared the ratios and time variance in linkage to care using the Kaplan-Meier estimator and Log rank tests. Cox proportional hazards regression models to evaluate factors associated with time variance in linkage. Results: At the end of 6 months, 78% of all respondents had linked into care, with differences across testing models. 84% (CI 81% to 87%, n=512) of individuals tested at facility-based site were linked to care compared to 69% (CI 65% to 74%, n=281) of individuals tested at mobile/outreach. The median time to linkage was 1 day (IQR: 1–7.5) for facility-based site and 6 days (IQR: 3–11) for mobile/outreach sites. Participants tested at facility-based site were 78% more likely to link than those tested at mobile/outreach when other variables were controlled (AHR=1.78; 95% CI 1.52 to 2.07). HIV status disclosure to family/relatives was significantly associated with linkage to care (AHR=2.64; 95% CI 2.05 to 3.39). Conclusions: Linkage to care after testing HIV positive in rural Tanzania has increased markedly since 2014, across testing models. Individuals tested at facility-based sites linked in significantly higher proportion and modestly sooner than mobile/outreach tested individuals. Mobile/outreach testing models bring HIV testing services closer to people. Strategies to improve linkage from mobile/outreach models are needed.
Data from: Aggression supersedes individual oxygen demand to drive group air-breathing in a social catfish
1) Group-living is widespread among animals and comes with numerous costs and benefits. To date, research examining group-living has focused on trade-offs surrounding foraging, while other forms of resource acquisition have been largely overlooked. 2) Air breathing has evolved in many fish lineages, allowing animals to obtain oxygen in hypoxic aquatic environments. Breathing air increases the threat of predation, so some species perform group air breathing, to reduce individual risk. Within species, air breathing can be influenced by metabolic rate as well as personality, but the mechanisms of group air breathing remain unexplored. It is conceivable that keystone individuals with high metabolic demand or intrinsic tendency to breathe air may drive social breathing, especially in hypoxia. 3) We examined social air breathing in African sharptooth catfish Clarias gariepinus, to determine whether individual physiological traits and spontaneous tendency to breathe air influence the behaviour of entire groups, and whether such influences vary in relation to aquatic oxygen availability. 4) We studied eleven groups of four catfish in a laboratory arena and recorded air-breathing behaviour, activity, and agonistic interactions at varying levels of hypoxia. Bimodal respirometry was used to estimate individual standard metabolic rate (SMR) and the tendency to utilise aerial oxygen when alone. 5) Fish took more air breaths in groups as compared to when they were alone, regardless of water oxygen content, and displayed temporally clustere air-breathing behaviour, consistent with existing definitions of synchronous air breathing. However, groups displayed tremendous variability in surfacing behaviour. Aggression by dominant individuals within groups was the main factor influencing air breathing of the entire group. There was no association between individual SMR, or the tendency to obtain oxygen from air when in isolation, and group air breathing. 6) For C. gariepinus, synchronous air breathing is strongly influenced by agonistic interactions, which may expose subordinate individuals to risk of predation. Influential individuals exerted an overriding effect on risk-taking by the entire group, for reasons independent of their physiological oxygen requirements. Overall, this illustrates that social context can obscure interactions between an individual's physiological and behavioural traits and their tendency to take risks to obtain resources.
Population fragmentation drives up genetic diversity in signals of individual identity
<p>Many species advertise their unique identity to conspecifics using dedicated individuality signals: one familiar example is human faces. But how unique in the global population do these signals need to be? While human faces are highly variable, each person interacts with many fewer individuals than are found in the total population. This raises the question of how evolutionary mechanisms drive up population-wide diversity when selection occurs at such a local level. We use an individual-based model in which individuals broadcast their identity and quality in separate, genetically-coded signals. Mimicking, for example, scent marking mammal species, females in the model assess males using the quality signal, then attempt to relocate the highest quality male using his identity signal. We ask how population fragmentation affects genetic diversity in the individual identity-signalling region under sexual selection, predicting one of two opposing outcomes: (1) divided populations evolve fewer signal variants globally, since repetition of signals is not costly when individuals interact only with local conspecifics, or (2) stochasticity in mutation and selection cause divergence among subpopulations, increasing the global number of signal variants. We show that local selection drives up global genetic diversity substantially in fragmented populations, even with extremely low rates of dispersal. Because new signal variants arise by mutation and then sweep through their subpopulation, a fragmented population has more global signal variation. This result furthers our understanding of how high levels of diversity in individuality signals are maintained.</p>
Data from: A local evaluation of the individual state-space to scale up Bayesian spatial capture recapture
1. Spatial capture-recapture models (SCR) are used to estimate animal density and to investigate a range of problems in spatial ecology that cannot be addressed with traditional non-spatial methods. Bayesian approaches in particular offer tremendous flexibility for SCR modelling. Increasingly, SCR data are being collected over very large spatial extents making analysis computational intensive, sometimes prohibitively so. 2. To mitigate the computational burden of large-scale SCR models, we developed an improved formulation of the Bayesian SCR model that uses local evaluation of the individual state-space (LESS). Based on prior knowledge about a species' home range size, we created square evaluation windows that restrict the spatial domain in which an individual's detection probability (detector window) and activity center location (AC window) are estimated. We used simulations and empirical data analyses to assess the performance and bias of SCR with LESS. 3. LESS produced unbiased estimates of SCR parameters when the AC window width was ≥5σ (σ: the scale parameter of the half-normal detection function), and when the detector window extended beyond the edge of the AC window by 2σ. Importantly, LESS considerably decreased the computation time needed for fitting SCR models. In our simulations, LESS increased the computation speed of SCR models up to 57 fold. We demonstrate the power of this new approach by mapping the density of an elusive large carnivore – the wolverine (Gulo gulo) – with an unprecedented resolution and across the species' entire range in Norway (more than 200 000 km2). 4. Our approach helps overcome a major computational obstacle to population and landscape-level SCR analyses. The LESS implementation in a Bayesian framework makes the customization and fitting of SCR accessible for practitioners that are working at scales that are relevant for conservation and management.
Data from: Individual performance in relation to cytonuclear discordance in a northern contact zone between long-toed salamander (Ambystoma macrodactylum) lineages
Cytonuclear discordance in contact zones between related lineages is common, with mitochondrial clines often being displaced from clines in nuclear allele frequency. Proposed explanations for such a pattern include adaptive introgression of mtDNA or a neutral wake of mtDNA being left behind following hybrid zone movement. However, studies investigating these hypotheses are rare. Our previous survey of genetic variation in the long-toed salamander (Ambystoma macrodactylum) highlighted a potential case of cytonuclear discordance between two lineages in western Canada. Here, we use additional markers and samples to clarify the extent of this discordance. We simultaneously assess the feeding performance of individuals in a common environment to test for an association between mitotype and individual performance. The genetic results confirm a general pattern of cytonuclear discordance in the focal region. However, we also observed more limited introgression of a diagnostic nuclear marker. Intriguingly, although there were differences in individual performance associated with the transition between mitotypes, these differences were not fully explained by mitotype. Instead, the lowest performance was observed in individuals demonstrating the greatest mismatch between mtDNA and all nuclear markers, suggesting the potential for cytonuclear incompatibilities to be acting. These results highlight the complexity of understanding the causes and consequences of mtDNA introgression and cytonuclear discordance in contact zones.
Data from: Selective increases in inter-individual variability in response to environmental enrichment in female mice
One manifestation of individualization is a progressively differential response of individuals to the non-shared components of the same environment. Individualization has practical implications in the clinical setting, where subtle differences between patients are often decisive for the success of an intervention, yet there has been no suitable animal model to study its underlying biological mechanisms. Here we show that enriched environment (ENR) can serve as a model of brain individualization. We kept 40 isogenic female C57BL/6JRj mice for 3 months in ENR and compared these mice to an equally sized group of standard-housed control animals, looking at the effects on a wide range of phenotypes in terms of both means and variances. Although ENR influenced multiple parameters and restructured correlation patterns between them, it only increased differences among individuals in traits related to brain and behavior (adult hippocampal neurogenesis, motor cortex thickness, open field and object exploration), in agreement with the hypothesis of a specific activity-dependent development of brain individuality.
Data from: 'Same procedure as last year?' Repeatedly tracked swifts show individual consistency in migration pattern in successive years
Individual migration pattern during non-breeding season is still a black box in many migratory birds. However, knowledge on both individual level and population level in migration and overwintering is fundamental to understand the life cycle of these birds and the constraints affecting them. We showed in a highly aerial migrant, the common swift Apus apus, that repeatedly tracked birds breeding at one site in Germany used the same individual-specific migration routes and wintering areas in subsequent years. In contrast, different individuals from the same breeding colony showed diverse movement patterns during non-breeding season suggesting that several suitable areas for overwintering coexist. We found lower variation in timing of autumn and spring migration within than between individuals. Our findings provide first indication of individual consistency but between-individual variation in migration pattern in a small non-passerine bird revealed by geolocators. This supports that swifts have diverse but individual-specific 'step-by-step' migration patterns revealing high flexibility through individual strategies.
Data from: Plasma carotenoid concentrations of incubating American kestrels (Falco sparverius) show annual, seasonal, and individual variation and explain reproductive outcome
In wild birds, the proximate and ultimate factors that affect circulating carotenoid concentrations remain poorly understood. We studied variation in plasma carotenoid concentrations across several scales: annual, seasonal, pair, territory and individual, and evaluated whether plasma carotenoid concentrations explained reproductive outcome of wild American kestrels (Falco sparverius). We sampled plasma carotenoid concentrations of 99 female and 80 male incubating kestrels from April to June in 2008 to 2012. Plasma carotenoid concentrations were explained by an interaction between year and sex, date, and random effects for pair and individual identity. In general, plasma carotenoid concentrations of males were significantly higher than females, but this depended on year. Within a breeding season, earlier nesting kestrels had higher carotenoid concentrations than later nesting kestrels, a pattern that is coincident with seasonal trends in local fitness. Pair and individual identity explained variation in carotenoid concentrations suggesting that carotenoid concentrations of mated birds were correlated, and some individuals consistently maintained higher carotenoid levels than others. Male carotenoid concentrations were positively associated with number of young fledged per pair. These results are consistent with the hypothesis that higher quality individuals have higher carotenoid levels compared to lower quality individuals, despite annual variations in carotenoid availability.
Data from: Empirical targets for acute hemodynamic management of individuals with spinal cord injury
Objective: To determine the hemodynamic conditions associated with optimal neurological improvement in acute traumatic spinal cord injury (SCI) individuals who had lumbar intrathecal catheters placed to measure cerebrospinal fluid pressure (CSFP). Methods: Ninety-two acute SCI individuals were enrolled in this multi-center prospective observational clinical trial. We monitored mean arterial pressure (MAP) and CSFP during the first week post-injury, and assessed neurologic function at baseline and six-months post-injury. We used relative risk iterations to determine transition points at which the likelihood of either improving neurologically or remaining unchanged neurologically was equivalent. These transition points guided our analyses where we examined the linear relationships between time spent within target hemodynamic ranges (i.e., clinical adherence) and neurological recovery. Results: Relative risk transition points for CSFP, MAP, and spinal cord perfusion pressure (SCPP) were linearly associated with neurological improvement and directed the identification of key hemodynamic target ranges. Clinical adherence to the target ranges was positively and linearly related to improved neurological outcomes. Adherence to SCPP targets, not MAP targets, was the best indicator of improved neurological recovery, which occurred with SCPP targets of 60-65 mmHg. Failing to maintain the SCPP within the target ranges was an important detrimental factor in neurologic recovery, particularly if the target range is set lower. Conclusion: We provide an empirical, data-driven approach to aid institutions in setting hemodynamic management targets that accept the real-life challenges of adherence to specific targets. Our results provide a framework to guide the development of widespread institutional management guidelines for acute traumatic SCI.
Data from: How individual Montagu's Harriers cope with Moreau's Paradox during the Sahelian winter
Hundreds of millions of Afro-Palaearctic migrants winter in the Sahel, a semi-arid belt south of the Sahara desert, where they experience deteriorating ecological conditions during their overwintering stay and have to prepare for spring migration when conditions are worst. This well-known phenomenon was first described by R.E. Moreau and is known ever since as Moreau's Paradox. However, empirical evidence of the deteriorating seasonal ecological conditions is limited and little is known on how birds respond. Montagu's Harriers Circus pygargus spend 6 months of the year in their wintering areas in the Sahel. Within the wintering season, birds move gradually to the south, visiting several distinct sites to which they are site-faithful in consecutive years. At the last wintering site, birds find themselves at the southern edge of the Sahelian zone and have no other options than facing deteriorating conditions. We tracked 36 Montagu's Harriers with GPS trackers to study their habitat use and behaviour during winter and collected data on the abundance of their main prey, grasshoppers, in Senegal. Since grasshopper abundance was positively related to vegetation greenness (measured as normalized difference vegetation index, NDVI), we used NDVI values as a proxy for prey abundance in areas where no field data were collected. Prey abundance (grasshopper counts and vegetation greenness) at wintering sites of Montagu's Harriers decreased during the wintering period. Montagu's Harriers responded to decreasing food availability by increasing their flight time during the second half of the winter. Individuals increased flight time more in areas with stronger declines in NDVI values, suggesting that lower food abundance required more intense foraging to achieve energy requirements. The apparent consequence was that Montagu's Harriers departed later in spring when their final wintering site had lower NDVI values and presumably lower food abundance and consequently arrived later at their breeding site. Our results confirmed the suggestions Moreau made 40 years ago: the late wintering period might be a bottleneck during the annual cycle with possible carry-over effects to the breeding season. Ongoing climate change with less rainfall in the Sahel region paired with increased human pressure on natural and agricultural habitats resulting in degradation and desertification is likely to make this period more demanding, which may negatively impact populations of migratory birds using the Sahel.
The effect of inter-and intraspecific competition on individual and population niche widths – a four-decade study on two interacting salmonids
<p>Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra- and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large-scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build-up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large-scale culling experiment and associated long-term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra- and interspecific competition have large and contrasting impacts on individual and population niches.</p>
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.