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Understanding how the nutritional properties of food resources drive foraging choices is important for the management and conservation of wildlife populations. For moose (Alces alces), recent experimental and observational studies during the winter have shown macronutrient balancing between available protein (AP) and highly metabolizable macronutrients (total non-structural carbohydrates [TNC] and lipids). Here, we combined the use of continuous-recording camera collars with plant nutrient analyses and forage availability measurements to obtain a detailed insight into the food and nutritional choices of three wild moose in Norway over a 5-day period in summer. We found that moose derived their macronutrient energy primarily from carbohydrates (74.2%), followed by protein (13.1%), and lipids (12.7%). Diets were dominated by deciduous tree browse (71%). Willows (Salix spp.) were selected for and constituted 51% of the average diet. Moose consumed 25 different food items during the study period of which 9 comprised 95% of the diet. Moose tightly regulated their intake of protein to highly metabolizable macronutrients (AP:TNC + lipids) to a ratio of 1:2.7 (0.37 ± 0.002SD). They did this by feeding on foods that most closely matched the target macronutrient ratio such as Salix spp., or by combining nutritionally imbalanced foods (complementary feeding) in a non-random manner that minimized deviations from the intake target. The observed patterns of macronutrient balancing aligned well with the findings of winter studies. Differential feeding on nutritionally balanced downy birch (Betula pubescens) leaves versus imbalanced twigs+leaves across moose individuals indicated that macronutrient balancing may occur on as fine a scale as foraging bites on a single plant species. Utilized forages generally met the suggested requirement thresholds for the minerals calcium, phosphorus, copper, molybdenum, and magnesium but tended to be low in sodium. Our findings offer new insights into the foraging behavior of a model species in ungulate nutritional ecology and contribute to informed decision-making in wildlife and forest management.

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Many theoretical treatments of foraging use energy as currency, with carbohydrates and lipids considered interchangeable as energy sources. However, herbivores must often synthesize lipids from carbohydrates since they are in short supply in plants, theoretically increasing the cost of growth. We tested whether a generalist insect herbivore (Locusta migratoria) can improve its growth efficiency by consuming lipids, and whether these locusts have a preferred caloric intake ratio of carbohydrate to lipid (C : L). Locusts fed pairs of isocaloric, isoprotein diets differing in C and L consistently selected a 2C : 1L target. Locusts reared on isocaloric, isoprotein 3C : 0L diets attained similar final body masses and lipid contents to locusts fed the 2C : 1L diet, but they ate more and had a ~12% higher metabolic rate, indicating an energetic cost for lipogenesis. These results demonstrate that some animals can selectively regulate carbohydrate-to-lipid intake and that consumption of dietary lipids can improve growth efficiency.

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Animals assimilate macronutrients and mineral nutrients in specific quantities and ratios to maximise fitness. To achieve this, animals must ingest different foods that contain the needed nutrients or facilitate the digestion of those nutrients. We explored how these multidimensional considerations affect the desert isopods (Hemilepistus reaumuri) curious food selection, using field and laboratory experiments. Wild isopods consumed three-fold more macronutrient-poor biological soil crust (BSC) than plant litter. Isopods tightly regulated macronutrient and calcium intake, but not phosphorus when eating the two natural foods and when artificial calcium and phosphorus sources substituted the BSC. Despite the equivalent calcium ingestion, isopods performed better when eating BSC compared to artificial foods. Isopods that consumed BSC sterilised by gamma-radiation ate more but grew slower than isopods that ate live BSC, implying that ingested microorganisms facilitate litter digestion. Our work highlights the need to reveal the multifaceted considerations that affect food-selection when exploring trophic-interactions.

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Anopheles gambiae and Anopheles coluzzii mosquitoes, two major malaria vectors in sub-Saharan Africa, exhibit selectivity among plant species as potential food sources. However, it remains unclear if their preference aligns with optimal nutrient intake and survival. Following an extensive screening of the effects of 31 plant species on An. coluzzii in Burkina Faso, we selected three species for their contrasting effects on mosquito survival, namely Ixora coccinea, Caesalpinia pulcherrima, and Combretum indicum. We assessed the sugar content of these plants and their impact on mosquito fructose positivity, survival, and insemination rate, using Anopheles coluzzii and Anopheles gambiae, with glucose 5% and water as controls. Plants displayed varying sugar content and differentially affected the survival, sugar intake, and insemination rate of mosquitoes. All three plants were more attractive to mosquitoes than controls, with An. gambiae being more responsive than An. coluzzii. Notably, C. indicum was the most attractive but had the lowest sugar content and offered the lowest survival, insemination rate, and fructose positivity. Our findings unveil a performance-preference mismatch in An. coluzzii and An. gambiae regarding plant food sources. Several possible reasons for this negative correlation between performance and preference are discussed.

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Mineral requirements are poorly described for most wildlife. Consequently, the role of forage minerals in movement and productivity are poorly understood for sedentary and migratory ungulates, such as reindeer and caribou (Rangifer tarandus). We applied estimates of maintenance, lactation, body mass change, and antler growth to production curves (body mass, daily intake, and milk yield) for female caribou to calculate their mineral requirements over summer. The total requirements (mg or g·d-1) were divided by the daily intake (kg·d-1) to estimate the minimum concentration of minerals required in the diet (mg or g·kg-1) to balance demand. The daily requirements (mg·d-1) of all minerals increased from parturition to the end of summer. The minimum dietary concentrations (mg·kg-1) of macro-minerals (Ca, P, Mg, Na, K) declined as food intake (kg·d-1) increased over summer. The minimum dietary concentrations (Fe, Mn, Cu, Zn) were heavily influenced by body mass gain, which increased through late lactation even though food intakes rose. Our modeling framework can be applied to other wild ungulates to assess the impacts of changing forage phenology, plant community compositions, or environmental disturbances on movement and productivity.

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As bees' main source of protein and lipids, pollen is critical for their development, reproduction, and health. Plant species vary considerably in the macronutrient content of their pollen, and research in bee model systems has established that this variation both modulates performance and guides floral choice. Yet, how variation in pollen chemistry shapes interactions between plants and bees in natural communities is an open question, essential for both understanding the nutritional dynamics of plant-pollinator mutualisms and informing their conservation. To fill this gap, we asked how pollen nutrition (relative protein and lipid content) sampled from 109 co-flowering plant species structured visitation patterns observed among 75 subgenera of pollen-collecting bees in the Great Basin/Eastern Sierra region (USA). We found that the degree of similarity in co-flowering plant species' pollen nutrition predicted similarity among their visitor communities, even after accounting for floral morphology and phylogeny. Consideration of pollen nutrition also shed light on the structure of this interaction network: Bee subgenera and plant genera were arranged into distinct, interconnected groups, delineated by differences in pollen macronutrient values, revealing potential nutritional niches. Importantly, variation in pollen nutrition alone (high in protein, high in lipid, or balanced) did not predict the diversity of bee visitors, indicating that plant species offering complementary pollen nutrition may be equally valuable in supporting bee diversity. Nutritional diversity should thus be a key consideration when selecting plants for habitat restoration, and a nutritionally explicit perspective is needed when considering reward systems involved in the community ecology of pollination.

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Diet and nutrition comprise a complex, multi-faceted interface between animal biology and food environments. With accumulating information on the many facets of this association arises a need for systems-based approaches that integrate dietary components and their links with ecology, feeding, post-ingestive processes and the functional and ecological consequences of these interactions. We briefly show how a modelling approach, nutritional geometry, has used the experimental control afforded in laboratory studies to begin to unravel these links. Laboratory studies, however, have limited ability to establish whether and how the feeding and physiological mechanisms interface with realistic ecological environments. We next provide an overview of observational field studies of free-ranging primates that have examined this, producing largely correlative data suggesting that similar feeding mechanisms operate in the wild as in the laboratory. Significant challenges remain, however, in establishing causal links between feeding, resource variation and physiological processes in the wild. We end with a more detailed account of two studies of temperate primates that have capitalized on the discrete variation provided by seasonal environments to strengthen causal inference in field studies and link patterns of intake to dynamics of nutrient processing. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

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Increased expenditure on the ejaculate is a taxonomically widespread male response to sperm competition. Increased ejaculate expenditure is assumed to come at a cost to future reproduction, otherwise males should always invest maximally. However, the life-history costs of strategic ejaculation are not well documented. Macronutrient intake is known to affect the trade-off between reproduction and lifespan. Intakes of protein and carbohydrate that maximize reproduction often differ from those that maximize lifespan. Here, we asked whether strategic expenditure on the ejaculate by male crickets, Teleogryllus oceanicus, is mediated by macronutrient intake, and whether it comes at a cost of reduced lifespan. Males were exposed to rival song throughout their lifespan or were held in a silent non-competitive environment. Males exposed to song had a higher intake of both protein and carbohydrate, they reached adulthood sooner, produced ejaculates of higher quality, and died sooner than males living in a silent environment. Our findings provide a rare example of both the mechanisms and life-history costs associated with strategic ejaculation.

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Ripe fleshy fruits contain not only nutrients but also a diverse array of secondary metabolites. Nutrients serve as a reward for mutualists, whereas defensive metabolites protect the fruit against pests and predators. The composition of these chemical traits is highly variable, both across different plants and even within repeating structures on the same individual plant. This intraspecific and intraindividual variation has important fitness consequences for both plants and animals, yet patterns of variation and covariation in nutrients and secondary metabolites are not well understood, especially at smaller scales. Here, we investigate the multiscale variation and covariation between nutrients and defensive metabolites in Piper sancti-felicis ripe fruits. Means and measures of variation of sugars, proteins, phenolics, and alkenylphenols vary greatly among plants, and at least 50% of the trait variation occurs at the intraindividual level. Also, we found that proteins, but not sugars, were correlated with phenolics and alkenylphenols at multiple scales, suggesting trait variation in protein content may be more constrained than sugars. Our findings emphasize the importance of examining patterns across scales and provide the groundwork to better understand how complex patterns of variation and covariation in nutrients and defensive metabolites shape ecological interactions surrounding fruits.

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Changes in our climate and physical environments are having profound effects on all aspects of human existence, and the ability to develop sustainable and resilient food systems is critical not just to the environment but to all aspects of human health. The Pediatric Growth and Nutrition Branch (PGNB) of the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the US National Institutes of Health has adopted a new paradigm to undergird the study of nutrition that recognizes the complex and reciprocal nature of the relationships between nutrition and health outcomes. This conceptual framework, termed the "nutritional ecology," views humans as complex biological systems interacting with both their internal and external environments. Herein, we focus on: (i) the reciprocal relationship between climate and environmental changes and food systems and their impact on food/nutrition security and health; and (ii) how PGNB is utilizing the "nutritional ecology" framework to support science addressing the interactions among health, nutrition, food systems, climate, and the environment.

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Nitrogen (N) deposition has increased substantially since the second half of the 20th century due to human activities. This increase of reactive N into the biosphere has major implications for ecosystem functioning, including primary production, soil and water chemistry and producer community structure and diversity. Increased N deposition is also linked to the decline of insects observed over recent decades. However, we currently lack a mechanistic understanding of the effects of high N deposition on individual fitness, species richness and community structure of both invertebrate and vertebrate consumers. Here, we review the effects of N deposition on producer-consumer interactions, focusing on five existing ecological frameworks: C:N:P ecological stoichiometry, trace element ecological stoichiometry, nutritional geometry, essential micronutrients and allelochemicals. We link reported N deposition-mediated changes in producer quality to life-history strategies and traits of consumers, to gain a mechanistic understanding of the direction of response in consumers. We conclude that high N deposition influences producer quality via eutrophication and acidification pathways. This makes oligotrophic poorly buffered ecosystems most vulnerable to significant changes in producer quality. Changes in producer quality between the reviewed frameworks are often interlinked, complicating predictions of the effects of high N deposition on producer quality. The degree and direction of fitness responses of consumers to changes in producer quality varies among species but can be explained by differences in life-history traits and strategies, particularly those affecting species nutrient intake regulation, mobility, relative growth rate, host-plant specialisation, ontogeny and physiology. To increase our understanding of the effects of N deposition on these complex mechanisms, the inclusion of life-history traits of consumer species in future study designs is pivotal. Based on the reviewed literature, we formulate five hypotheses on the mechanisms underlying the effects of high N deposition on consumers, by linking effects of nutritional ecological frameworks to life-history strategies. Importantly, we expect that N-deposition-mediated changes in producer quality will result in a net decrease in consumer community as well as functional diversity. Moreover, we anticipate an increased risk of outbreak events of a small subset of generalist species, with concomitant declines in a multitude of specialist species. Overall, linking ecological frameworks with consumer life-history strategies provides a mechanistic understanding of the impacts of high N deposition on producer-consumer interactions, which can inform management towards more effective mitigation strategies.

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Body nutrient profiles in ecological studies allow for relating the nutritional status of consumers and their effects on the movement and retention of elements in ecosystems, as well as reflecting feeding conditions and habitat quality. This study compared the detailed whole-body nutrient composition (macronutrients, minerals, fatty acids and amino acids) of two omnivorous natives Orestias killifish from Lake Titicaca (Orestias agassizii and Orestias luteus, Valenciennes), the largest lake in the Andes, as an indirect tool to understand differences in their feeding ecology. Although both species are usually described as omnivorous fish, both have amphipods (Hyalella spp) as their main food source. Our results showed that both killifish had a comparable macronutrient composition, and the mineral concentrations of Mg, P and Ca (reflecting bony structures) differed between them. Many of the saturated fatty acids were significantly lower in O. luteus, and O. agassizii had higher concentrations of cis-vaccenic acid (18:1n11 (cis)), supporting the idea of a higher algal contribution to the diet of this fish. The lower histidine and higher taurine concentrations in O. agassizii compared with O. luteus (independent of body size) may reflect its ubiquitous behaviour and plasticity. This study shows how whole-body nutrient analysis can identify differences in feeding ecology and feeding behaviour between related species.

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Two mutually unexclusive hypotheses prevail in the theory of nutritional ecology: the balanced diet hypothesis states that consumers feed on different food items because they have complementary nutrient and energy compositions. The toxin-dilution hypothesis poses that consumers feed on different food items to dilute the toxins present in each. Both predict that consumers should not feed on low-quality food when ample high-quality food forming a complete diet is present. We investigated the diet choice of Phytoseiulus persimilis, a predatory mite of web-producing spider mites. It can develop and reproduce on single prey species, for example the spider mite Tetranychus urticae. A closely related prey, T. evansi, is of notorious bad quality for P. persimilis and other predator species. We show that juvenile predators feeding on this prey have low survival and do not develop into adults. Adults stop reproducing and have increased mortality when feeding on it. Feeding on a mixed diet of the two prey decreases predator performance, but short-term effects of feeding on the low-quality prey can be partially reversed by subsequently feeding on the high-quality prey. Yet, predators consume low-quality prey in the presence of high-quality prey, which is in disagreement with both hypotheses. We suggest that it is perhaps not the instantaneous reproduction on single prey or mixtures of prey that matters for the fitness of predators, but that it is the overall reproduction by a female and her offspring on an ephemeral prey patch, which may be increased by including inferior prey in their diet.

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Humans are increasing the environmental availability of historically limited nutrients, which may significantly influence organismal performance and behavior. Beneficial or stimulatory responses to increases in nitrogen availability (i.e., nitrogen limitation) are generally observed in plants but less consistently in animals. One possible explanation is that animal responses to nitrogen enrichment depend on how nitrogen intake is balanced with sodium, a micronutrient crucial for animals but not plants. We tested this idea in the cabbage white butterfly (Pieris rapae), a species that frequently inhabits nutrient-enriched plants in agricultural settings and roadside verges. We asked (1) whether anthropogenic increases in sodium influence how nitrogen enrichment affects butterfly performance and (2) whether individuals can adaptively adjust their foraging behavior to such effects. Larval nitrogen enrichment enhanced growth of cabbage white larvae under conditions of low but not high sodium availability. In contrast, larval nitrogen enrichment increased egg production of adult females only when individuals developed with high sodium availability. Ovipositing females preferred nitrogen-enriched leaves regardless of sodium availability, while larvae avoided feeding on nitrogen-enriched leaves elevated in sodium. Our results show that anthropogenic increases in sodium influence whether individuals benefit from and forage on nitrogen-enriched resources. Yet, different nitrogen-to-sodium ratios are required to optimize larval and adult performance. Whether increases in sodium catalyze or inhibit benefits of nitrogen enrichment may depend on how evolved nutrient requirements vary across stages of animal development.

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Early-life conditions can have long-term fitness consequences. However, it is still unclear what optimal rearing conditions are, especially for long-lived carnivores. A more diverse diet ('balanced diet') might optimize nutrient availability and allow young to make experiences with a larger diversity of prey, whereas a narrow diet breadth ('specialized diet') might result in overall higher energy net gain. A diet that is dominated by a specific prey type (i.e. fish, 'prey type hypothesis') might be beneficial or detrimental, depending for example, on its toxicity or contaminant load. Generalist predators such as the white-tailed eagle Haliaeetus albicilla provide an interesting possibility to examine the relationship between early life diet and long-term offspring survival. In the Åland Islands, an archipelago in the Baltic Sea, white-tailed eagles live in various coastal habitats and feed on highly variable proportions of birds and fish. We use data from 21,116 prey individuals that were collected from 120 territories during the annual surveys, to examine how early-life diet is associated with apparent annual survival of 574 ringed and molecular-sexed eaglets. We supplement this analysis by assessing the relationships between diet, reproductive performance and nestling physical condition, to consider whether they are confounding with possible long-term associations. We find that early-life diet is associated with long-term fitness: Nestlings that are fed a diverse diet are in lower physical condition but have higher survival rates. Eagles that are fed more fish as nestlings have lower survival as breeding-age adults, but territories associated with fish-rich diets have higher breeding success. Our results show that young carnivores benefit from a high diversity of prey in their natal territory, either through a nutritional or learning benefit, explaining the higher survival rates. The strong relationship between early-life diet and adult survival suggests that early life shapes adult foraging decisions and that eating fish is associated with high costs. This could be due to high levels of contaminants or high competition for fish-rich territories. Long-lasting consequences of early-life diet are likely not only limited to individual-level consequences but have the potential to drive eco-evolutionary dynamics in this population.

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The forensically important genus Thanatophilus Leach, 1815 (Coleoptera: Silphidae) is a widespread group of carrion beetles that occupies the Holarctic and Afrotropical realms. It has recently received more recognition, as its species are frequently detected on large carrion, including humans, and can be useful in estimating the time of colonization (TOC) and the post-mortem interval (PMI). The immature stages of Thanatophilus sinuatus (Fabricius, 1775) were reared on three different meat diets (pork liver, pork muscle, and chicken muscle). Diet influence on some of the essential life history traits of the species was examined for different populations. Our findings indicated an accelerated development on pork muscle followed closely by pork liver and a prolonged development on chicken muscle. The diet significantly affected the size, and the body condition (weight/ size) as both pork muscle and liver produced individuals in better physical condition (larger and heavier). The impact of two cyclic photoperiod regimes (16 h Light (L): 8 h Dark (D) and 12 h L: 12 h D) was further evaluated and indicated no significant variability.

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Lower plant resistance to herbivores following domestication has been suggested as the main cause for higher feeding damage in crops than in wild progenitors. While herbivore compensatory feeding has also been proposed as a possible mechanism for raised damage in crops with low nutritional quality, predictions regarding the effects of plant domestication on nutritional quality for herbivores remain unclear. In particular, data on primary metabolites, even major macronutrients, measured in the organs consumed by herbivores, are scarce. In this study, we used a collection of 10 accessions of wild ancestors and 10 accessions of modern progenies of Triticum turgidum to examine whether feeding damage and selectivity by nymphs of Locusta migratoria primarily depended on five leaf traits related to structural resistance or nutrient profiles. Our results unexpectedly showed that locusts favored wild ancestors over domesticated accessions and that leaf toughness and nitrogen and soluble protein contents increased with the domestication process. Furthermore, the quantitative relationship between soluble protein and digestible carbohydrates was found to poorly meet the specific requirements of the herbivore, in all wheat accessions, both wild and modern. The increase in leaf structural resistance to herbivores in domesticated tetraploid wheat accessions suggested that resource allocation trade-offs between growth and herbivory resistance may have been disrupted by domestication in the vegetative organs of this species. Since domestication did not result in a loss of nutritional quality in the leaves of the tetraploid wheat, our results rather provides evidence for a role of the content of plants in nonnutritive nitrogenous secondary compounds, possibly deterrent or toxic, at least for grasshopper herbivores.

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Animals are integrated into the wider ecosystem via their foraging and behavior. The compensation hypothesis predicts that animals target their foraging efforts (i) toward nutrients that are scarce in the environment and (ii) toward nutrients that are not present in the usual diet of species, which varies across trophic levels. Understanding how foraging for resources varies locally, such as across habitat strata, and trophic levels will help to elucidate the links between the local environment and communities to the ecological functions that animals mediate. We examined whether the relative resource use of ants varies consistently along a habitat strata gradient and across trophic levels across Neotropical biomes. We placed 4500 baited tubes, each containing one of five liquid resources (sugar, amino acid, lipid, sodium, and distilled water) in one of three habitat strata (subterranean, epigaeic, and arboreal) across 60 transects in Amazon, Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal biomes. We assessed the relative resource use of all ants across the habitat strata and among two different trophic groups across biomes. The relative preference for sugar increased from subterranean to arboreal strata in all biomes, while the relative preference for lipids decreased at this gradient in five biomes. We also found that in general sugar-consuming ants foraged more for sugar and less for lipids than predatory ants across biomes. Conversely, we found no consistency across biomes in nutrient preference of amino acid and sodium across habitat strata or trophic levels. Overall, our results indicate sugar limitation in the arboreal stratum and lipid limitation on the ground across biomes and that the trophic level of ants strongly determines their foraging efforts-possibly because ants try to fix their dietary nutrient imbalances. Hence, our findings suggest strong local niche partitioning of sugar and lipid use across habitat strata and trophic levels and that other large spatial scale processes influence the local amino acid and sodium dynamics.

Os animais se integram nos ecossistemas pelos seus esforços e comportamento de forrageio. A hipótese da compensação prevê que os animais direcionam seus esforços de forrageio para (i) nutrientes que são escassos no ambiente e (ii) para nutrientes que não estão presentes em sua dieta, que variam entre os níveis tróficos. Assim, entender como a busca de recursos varia localmente entre os estratos de habitat e entre níveis tróficos, ajudará a entender as conexões entre o ambiente e suas comunidades com as funções ecológicas mediadas pelos animais. Avaliamos se o uso relativo de recursos das formigas varia consistentemente em um gradiente de estratos de habitat e em diferentes níveis tróficos nos biomas Neotropicais. Disponibilizamos um total de 4.500 tubos contendo um de cinco recursos líquidos (açúcar, aminoácido, lipídio, sódio e água destilada) em três estratos de habitat (subterrâneo, epigéico e arbóreo) em 60 transectos distribuídos nos biomas Amazônia, Mata Atlântica, Caatinga, Cerrado, Pampa e Pantanal. Avaliamos o uso relativo de recursos de todas as formigas ao longo dos estratos de habitat e entre dois grupos tróficos diferentes nos biomas. A preferência relativa por açúcar aumentou do estrato subterrâneo para o arbóreo em todos os biomas, enquanto a preferência relativa por lipídios diminuiu neste gradiente em cinco biomas. Também descobrimos que, em geral, as formigas consumidoras de açúcar procuram mais açúcar e menos lipídios do que as formigas predadoras nos biomas. Por outro lado, não encontramos consistência entre biomas na preferência nutricional de aminoácidos e sódio nos estratos de habitat ou níveis tróficos. No geral, nossos resultados indicam limitação de açúcar no estrato arbóreo e limitação de lipídios no solo em todos os biomas e que o nível trófico das formigas determina fortemente seus esforços de forrageamento - possivelmente porque as formigas tentam corrigir seus desequilíbrios de nutrientes na dieta. Portanto, nossas descobertas sugerem forte partição de nicho local de uso de açúcar e lipídios em estratos de habitat e níveis tróficos e que outros processos de grande escala espacial influenciam a dinâmica local de aminoácidos e sódio.

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Dietary specialisations are important determinants of ecological structure, particularly in species with high per-capita trophic influence like marine apex predators. These species are, however, among the most challenging in which to establish spatiotemporally integrated diets. We introduce a novel integration of stable isotopes with a multidimensional nutritional niche framework that addresses the challenges of establishing spatiotemporally integrated nutritional niches in wild populations, and apply the framework to explore individual diet specialisation in a marine apex predator, the white shark Carcharodon carcharias. Sequential tooth files were sampled from juvenile white sharks to establish individual isotopic (δ-space; δ13 C, δ15 N, δ34 S) niche specialisation. Bayesian mixing models were then used to reveal individual-level prey (p-space) specialisation, and further combined with nutritional geometry models to quantify the nutritional (N-space) dimensions of individual specialisation, and their relationships to prey use. Isotopic and mixing model analyses indicated juvenile white sharks as individual specialists within a broader, generalist, population niche. Individual sharks differed in their consumption of several important mesopredator species, which suggested among-individual variance in trophic roles in either pelagic or benthic food webs. However, variation in nutrient intakes was small and not consistently correlated with differences in prey use, suggesting white sharks as nutritional specialists and that individuals could use functionally and nutritionally different prey as complementary means to achieve a common nutritional goal. We identify how degrees of individual specialisation can differ between niche spaces (δ-, p- or N-space), the physiological and ecological implications of this, and argue that integrating nutrition can provide stronger, mechanistic links between diet specialisation and its intrinsic (fitness/performance) and extrinsic (ecological) outcomes. Our time-integrated framework is adaptable for examining the nutritional consequences and drivers of food use variation at the individual, population or species level.

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AbstractEnvironmental effects on learning are well known, such as cognition that is mediated by nutritional consumption. Less known is how seasonally variable environments affect phenological trajectories of learning. Here, we test the hypothesis that nutritional availability affects seasonal trajectories of population-level learning in species with developmentally plastic cognition. We test this in bumble bees (Apidae: Bombus), a clade of eusocial insects that produce individuals at different time points across their reproductive season and exhibit organ developmental plasticity in response to nutritional consumption. To accomplish this, we develop a theoretical model that simulates learning development across a reproductive season for a colony parameterized with observed life history data. Our model finds two qualitative seasonal trajectories of learning: (1) an increase in learning across the season and (2) no change in learning across the season. We also find these two qualitative trajectories revealed by empirical learning data; the proportion of workers successfully completing a learning test increases across a season for two bumble bee species (Bombus auricomus, Bombus pensylvanicus) but does not change for another three (Bombus bimaculatus, Bombus griseocollis, Bombus impatiens). This study supports the novel consideration that resources affect seasonal trajectories of population-level learning in species with developmentally plastic cognition.

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