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The Multidimensional Nutritional Niche

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Abstract

The dietary generalist-specialist distinction plays a pivotal role in theoretical and applied ecology, conservation, invasion biology, and evolution and yet the concept remains poorly characterised. Diets, which are commonly used to define niche breadth, are almost exclusively considered in terms of foods, with little regard for the mixtures of nutrients and other compounds they contain. We use nutritional geometry (NG) to integrate nutrition with food-level approaches to the dietary niche and illustrate the application of our framework in the important context of invasion biology. We use an example that involves a model with four hypothetical nonexclusive scenarios. We additionally show how this approach can provide fresh theoretical insight into the ways nutrition and food choices impact trait evolution and trophic interactions.

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... In optimal foraging theory (41), animals maximize energy as a common currency for choices ("energy maximization"). Alternatively, animals may balance the intake of different nutrients ("nutrient balancing") (42)(43)(44) or choose food based on the reward value of specific sensory and nutrient components ("nutrient reward") (7,45). We evaluated these strategies in a repeated-choice paradigm suited for neurophysiological recordings and derived hypotheses about the neuronal mechanisms for nutrient-sensitive decision-making (e.g., "energy-tracking neurons" versus "nutrient-value neurons"-Discussion). ...
... Reference Points. Balanced nutrient intake (i.e., maintaining stable proportions of nutrients) is crucial for health benefits and a choice strategy adopted by various animal species (42)(43)(44). Therefore, rather than only considering fat and sugar independently, we used the proportion-based Geometric Framework for Nutrition (44,49) to model the relative fat and sugar intake in proportion of total consumed energy. ...
... One influential view in ecology suggests energy as a common currency that animals maximize (41). More recent studies identified nutrient-balancing as a strategy adopted by various animals in the wild (42)(43)(44)49). In our experiments, nutrient balances from monkeys' choices were strongly offer dependent (Fig. 5). ...
Article
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Significance Preferences for foods high in sugar and fat are near universal and major contributors to obesity. Additionally, human food choices are sophisticated and individualistic: we choose by evaluating a food’s nutrients and sensory features and trading them against quantity and cost. To understand the mechanisms behind human-like food choices, we developed an experimental paradigm in which monkeys chose nutrient rewards offered in varying quantities. Resembling human suboptimal eating, the monkeys’ fat and sugar preferences shifted their nutrient balance away from dietary reference points. Formally defined economic values for specific nutrients and food textures explained the monkeys’ preferences and individual differences. Our findings show how human-like preferences derive from biologically critical food components and open up investigations of underlying neural mechanisms.
... The ecological niche of a species describes the range of environmental conditions and resources that are required for its persistence; it positions each species in relation to others in ecosystem space [83], taking into account physical conditions, such as climate, and food resources [84]. The nutritional niche is nested within the ecological niche and describes a specific proportion and ratio of nutrients which enable maximum growth, development, performance, and fitness ( Figure 2A) [85][86][87]. Notably, precise values of the optimal niche can change with the internal state of an animal (e.g., larva versus adult) and with changing environmental conditions [87]. The nutritional niche can consequently be described by a multidimensional geometric space defined by food chemistry where each axis represents a nutrient (e.g., specific amino acids, chemical elements, or group of components) that are functionally relevant to a species (i.e., they are required for their development, survival, and reproduction [37,87,88]) ( Figure 2). ...
... The nutritional niche is nested within the ecological niche and describes a specific proportion and ratio of nutrients which enable maximum growth, development, performance, and fitness ( Figure 2A) [85][86][87]. Notably, precise values of the optimal niche can change with the internal state of an animal (e.g., larva versus adult) and with changing environmental conditions [87]. The nutritional niche can consequently be described by a multidimensional geometric space defined by food chemistry where each axis represents a nutrient (e.g., specific amino acids, chemical elements, or group of components) that are functionally relevant to a species (i.e., they are required for their development, survival, and reproduction [37,87,88]) ( Figure 2). ...
... Notably, precise values of the optimal niche can change with the internal state of an animal (e.g., larva versus adult) and with changing environmental conditions [87]. The nutritional niche can consequently be described by a multidimensional geometric space defined by food chemistry where each axis represents a nutrient (e.g., specific amino acids, chemical elements, or group of components) that are functionally relevant to a species (i.e., they are required for their development, survival, and reproduction [37,87,88]) ( Figure 2). Within this space, some combinations of nutrients are more important for performance and fitness than others. ...
Article
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Wild bee populations are declining due to human activities, such as land use, which strongly affect the composition and diversity of available plants and food sources. The chemical composition of food (i.e. nutrition), in turn, determines health, resilience and fitness of bees. However, for pollinators, the term health is recent and subject to debate as is the interaction between nutrition and wild bee health. We define bee health as a multidimensional concept in a novel integrative framework linking bee biological traits (physiology, stoichiometry and disease) and environmental factors (floral diversity, nutritional landscapes). Linking information on tolerated nutritional niches and health in different bee species will allow us to better predict their distribution and responses to environmental change and thus support wild pollinator conservation.
... Foods are parceled as mixtures of many nutrients and other compounds that fuel the consumer's body (Atwater, 1902;Raubenheimer et al., 2009). Nutrients provide the mechanistic link between an animal's foraging choices, fitness and their dietary niche breadth (Machovsky-Capuska et al., 2016a. Bignert et al. (1993) highlighted the importance of exploring the relation between nutrients and pollutants in a sensitive, robust and quantitative framework. ...
... Nutritional ecology focuses on exploring the relationships between nutrition, behavior, pollutants, ecology and physiology (Martinez del Rio and Cork, 1997;Raubenheimer et al., 2009). The proportions-based nutritional geometry was designed to deal with the complexities of understanding how wild animals meet their nutritional requirements in environments where multiple foods of differing nutritional composition are available (Raubenheimer, 2011;Raubenheimer et al., 2015;Machovsky-Capuska et al., 2016a, Machovsky-Capuska et al., 2016bDenuncio et al., 2017). Being multidimensional, proportions-based nutritional geometry provides an opportunity to integrate micro- (Nie et al., 2014) and macro-nutrients (reviewed in Simpson and Raubenheimer, 2012;Machovsky-Capuska et al., 2018), secondary metabolites and toxins , and plastics (Machovsky-Capuska et al., 2019 into a broader ecological context. ...
... To geometrically define prey and the diet, % P is plotted against % L. Considering that the three components in the mixture sum to 100%, plotting % P (first axis) and % L (second axis) will automatically reflect the value of % W in the third axis (Raubenheimer, 2011). The minimum prey composition niche (all prey consumed by dolphins, Machovsky-Capuska et al., 2016a) is delineated by the grey area. The overall macronutrient intake of the diet of this population was 16.3P:6.3L:77.4W ...
Article
Bioaccumulation of Hg and Cd from food is a complex ecological process that has been oversimplified in the past. Common dolphins (Delphinus delphis) provide a powerful model to biomonitor metal concentrations in marine environments worldwide. We combined proportions-based nutritional geometry with metal analysis, stomach content analysis and the proximate composition of prey, to yield novel insights into the accumulation of Hg and Cd. Our analysis showed an age-related accumulation trend for Cd and Hg in kidney and liver, with highest concentrations found at 18 years of age. When view through the lens of nutritional ecology, Argentine anchovy (58.1 Mass %) and South American long-finned squid (22.7 Mass %), provided most of the dietary intake of protein (P) and lipids (L) (P:L ratio = 2.6:1.0) and also represented the main source for Cd and Hg levels accumulated in their bodies. This study presents unprecedented evidence on metal accumulation in relation to age and nutritional intake in a marine predator.
... For instance, in most cases we cannot readily link the intrinsic physiological requirements and tolerances of potential invaders [i.e., fundamental nutritional niches (FNNs); see Glossary)] to the availability of foods in introduced habitats that satisfy these FNNs (i.e., realized nutritional niches, RNNs). The emerging field of nutritional geometry (NG) can be used to make these links and thus provides a new research agenda for unlocking greater predictive power in the field of invasion biology [6][7][8]. ...
... Broad diets in animals and broad soil-quality tolerances in plants have classically been thought to predict the ecological generalism that governs invasive success [8][9][10][11]. However, although foodlevel estimates of diet breadth and qualitative descriptions of soils can be correlated with sustained population growth over large areas [12][13][14], they can provide an incomplete picture when making general predictions about the invasive potential of novel species [15][16][17]. ...
... Indeed, NG studies have repeatedly shown that organisms from slime molds [38] to humans [39,40] simultaneously regulate multiple nutrients (e.g., proteins, carbohydrates, lipids; i.e., nutrient regulation) when foraging in laboratory experiments and in natural field conditions [41]. Recent advances also provide powerful graphical tools to visualize this nutritional colimitation, and a theoretical framework to explain the variation in terms of 'Hutchinsonian' fundamental and realized niches [8,17]. These nutritional niche dimensions have further been linked to traits governing invasive success, including the capacity to resist environmental stress [42] and express behavioral aggression [43,44]. ...
Article
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Despite mounting calls for predictive ecological approaches rooted in physiological performance currencies, the field of invasive species biology has lagged behind. For instance, successful invaders are often predicted to consume diverse foods, but the nutritional complexity of foods often leaves food-level analyses short of physiological mechanisms. The emerging field of nutritional geometry (NG) provides new theory and empirical tools to predict invasive potential based on fundamental and realized nutritional niches. We review recent advances and synthesize NG predictions about behavioral traits that favor invasive establishment, and evolutionary dynamics that promote invasive spread. We also provide practical advice for applying NG approaches, and discuss the power of nutrition to achieve a more predictive invasion biology that explicitly integrates physiological mechanisms.
... A difference in the amounts of food eaten in the two tests will therefore reveal the extent of food limitation in the field (the level of hunger), and a difference in the proportion of macronutrients selected will indicate if particular macronutrients were in short supply and therefore subject to compensatory feeding (Mayntz et al., 2005). The intake target selected in the second test is equal to the fundamental macronutritional niche position (Behmer & Joern, 2008;Machovsky-Capuska et al., 2016a) though it says nothing of the fundamental macronutritional niche width. The intake targets selected in the first test reflect the individual realized macronutritional niche positions and the distribution of intake targets reflects the realized macronutritional niche width (Toft et al., 2019). ...
... It has been suggested that co-existing species of the same assemblage may segregate ecologically by choosing foods of different macronutrient composition (Behmer & Joern, 2008;Machovsky-Capuska et al., 2016a). Thus, co-existing Melanoplus grasshopper species self-selected diets with significantly different carbohydrate:protein ratio (Behmer & Joern, 2008), and carabid beetles from agricultural fields self-selected diets of different lipid:protein ratios (Toft et al., 2019). ...
... some species and the exclusion of Blaptica adults, and thus cannot be considered final. Given that the study included species belonging to different assemblages and different life stages (though all in the omnivore guild), differential choice of food types may also be an important niche segregating mechanism (differences in 'food exploitation' sensu Machovsky-Capuska et al., 2016a), though we have no information about the species' natural diets to substantiate this suggestion. An interesting finding is that the species in the field (realized niche) segregated only two-dimensionally (along a protein-sugar axis) whereas their fundamental niches segregated three-dimensionally (i.e. ...
Article
1. Carnivores are often food and/or macronutrient limited in their natural habitats, but whether they are limited mostly by protein or lipid is still a matter of controversy. As many predators and carnivorous scavengers also include plant material in their diet (omnivory), carbohydrate limitation is also possible. 2. The authors used a recently described double‐test procedure to test for food and macronutrient limitation in five co‐existing species of predators and omnivorous scavengers from Uruguay (two crickets: Gryllus sp. and Miogryllus verticalis; two cockroaches: Blatta orientalis and Blaptica dubia and a harvestman: Acanthopachylus aculeatus). 3. The authors found that the two crickets and one cockroach were food limited and one cockroach was non‐protein (lipid) limited in the field. The harvestman showed a dramatic change in food limitation between two dates separated by only 3 weeks, but was non‐protein (lipid) limited over both dates. From all species, the harvestman showed the highest self‐selected intake of carbohydrates (27%), indicating a high level of omnivory. In contrast, the two cockroaches selected a surprisingly low proportion of carbohydrates (13–14%), while the crickets were intermediate (14–19%). The authors hypothesize that these omnivores are more carnivorous in the wild than expected from studies of laboratory populations. 4. Though individuals were collected from the same habitats and all species self‐selected macronutrient ratios characteristic of omnivorous carnivores, they showed different patterns of food and macronutrient limitation, reflecting species' niche segregation and individual differences in foraging success.
... Proportions-based NGF was recently applied in a novel development of niche theory, establishing a new multidimensional nutritional niche framework (MNNF) for assessing dietary generalism (Machovsky-Capuska et al., 2016d). Under this framework, dietary classification along a generalistspecialist spectrum might differ at the levels of prey eaten ('prey composition niche') and the nutrient content of the diet given ecological constraints ('realised nutritional niche'). ...
... Under this framework, dietary classification along a generalistspecialist spectrum might differ at the levels of prey eaten ('prey composition niche') and the nutrient content of the diet given ecological constraints ('realised nutritional niche'). Species' classifications as generalists or specialists can predict their success across environmental contexts (Slatyer et al., 2013;Machovsky-Capuska et al., 2016d;Senior et al., 2016). Certainly, knowledge of predator nutritional niche breadths and requirements could assist in understanding their responses to variations in prey availability and composition (Machovsky-Capuska et al., 2016d). ...
... Species' classifications as generalists or specialists can predict their success across environmental contexts (Slatyer et al., 2013;Machovsky-Capuska et al., 2016d;Senior et al., 2016). Certainly, knowledge of predator nutritional niche breadths and requirements could assist in understanding their responses to variations in prey availability and composition (Machovsky-Capuska et al., 2016d). Several studies on marine predators, including seabirds (Tait et al., 2014;Machovsky-Capuska et al., 2016b,c;Miller et al., 2017), cetaceans (Denuncio et al., 2017), fish, sharks and pinnipeds (Machovsky-Capuska and Raubenheimer, 2020) have now drawn from the MNNF to provide fresh insights into their nutritional ecology. ...
Article
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Establishing diets and dietary generalism in marine top predators is critical for understanding their ecological roles and responses to environmental fluctuations. Nutrition plays a key mediatory role in species-environment interactions, yet descriptions of marine predators’ diets are usually limited to the combinations of prey species consumed. Here we combined stomach contents analysis (n = 40), literature prey nutritional data and a multidimensional nutritional niche framework to establish the diet and niche breadths of white sharks (Carcharodon carcharias; mean ± SD precaudal length = 187.9 ± 46.4 cm, range = 123.8–369.0 cm) caught incidentally off New South Wales (NSW), Australia. Our nutritional framework also facilitated the incorporation of existing literature diet information for South African white sharks to further evaluate nutritional niches across populations and sizes. Although teleosts including pelagic eastern Australian salmon (Arripis trutta) were the predominant prey for juvenile white sharks in NSW, the diversity of benthic and reef-associated species and batoids suggests regular benthic foraging. Despite a small sample size (n = 18 and 19 males and females, respectively), there was evidence of increased batoid consumption by males relative to females, and a potential size-based increase in shark and mammal prey consumption, corroborating established ontogenetic increases in trophic level documented elsewhere for white sharks. Estimated nutritional intakes and niche breadths did not differ among sexes. Niche breadths were also similar between juvenile white sharks from Australia and South Africa. An increase in nutritional niche breadth with shark size was detected, associated with lipid consumption, which we suggest may relate to shifting nutritional goals linked with expanding migratory ranges.
... Although the different types of food (hereafter prey) and their energy content have been extensively used to characterize the dietary niche of a species (Lindeman, 1942;Stephens and Krebs, 1986), an extensive body of literature suggests that modelling nutrients will enable to explore the intricacies of foraging, physiology, and ecology (Machovsky-Capuska et al., 2016a;Raubenheimer et al., 2009). To demonstrate the importance of a nutritional dimension into the levels of prey eaten ("prey composition niche") and the nutrient content of the dietary niche under ecological constraints ("realized nutritional niche"), an innovative Multidimensional Nutritional Niche Framework (MNNF) was recently developed (Machovsky-Capuska et al., 2016b). This nutritionally explicit framework is particularly relevant to marine apex predators known to forage in complex and fluctuating marine environments (Machovsky-Capuska et al., 2016a;Machovsky-Capuska and Raubenheimer, 2020). ...
... Although ecological research has extensively focussed on the taxonomic classification of the prey species consumed (i.e. type of prey), the use of a MNNF can help to understand the diversity of nutrients within their prey that a species is capable of exploiting in their ecological niches (Machovsky-Capuska et al., 2016b). In our study, we found that SASL and SAFS exhibit a high prey composition niche overlap (0.75), demonstrating that they consumed different prey species but with similar macronutrient composition ranges (P:L ratios from 1.8:1.0 to 36.1:1.0). ...
... Prey composition niches (all the prey consumed by a species,Machovsky-Capuska et al., 2016b) for South American sea lions (SASL) and South American fur seals (SAFS) from the Warm Temperate Southwestern Atlantic biogeographic province (WTSA). A) PNG showing the proximate composition of the prey consumed by SASL (grey hollow circles), SAFS (black triangles) and common to both species (black stars). ...
Article
Niche segregation has been recognized as a valuable mechanism for sympatric species to reduce interspecific competition and facilitate coexistence. The differential use of habitats is one of the behavioural mechanisms that may shape coexistence among marine predators. In this study, we provide a dietary and nutritional assessment of two pinnipeds, the South American sea lion (SASL) and the South American fur seal (SAFS) and explore their sympatric coexistence within the Warm Temperate Southwestern Atlantic biogeographic province (WTSA province). Pelagic prey species within the WTSA province showed significantly higher proportional composition of lipids than demersal counterparts, evidencing a nutritional variability in a vertical dimension accessible to marine predators. By modelling the dietary niches of these pinnipeds through a nutritional lens, we showed high overlapping prey composition niche breadths suggesting that both species consumed prey with similar nutritional composition; however, distinct realized nutritional niches showed that diets are likely shaped by differences in foraging behaviours. The SAFS combined pelagic and demersal prey, whereas SASL mostly preyed upon demersal species. This paper provides crucial information on how nutritional variability in the water column likely drives the feeding strategies of both pinnipeds in the WTSA province. Given that this variation can influence the stability of the contrasting population trends shown by these two pinnipeds, nutritional dynamics must be taken into consideration when defining conservation strategies.
... Description of animals' trophic niches provides clues to understanding interactions between species in biological communities that cannot easily be observed. The macronutrient niche (Behmer & Joern, 2008;Machovsky-Capuska, Senior, et al., 2016) is a recently developed concept in niche ecology of animals related in particular to non-specialist feeders that compose a diet from a diversity of foods, that is, herbivores from different food plants, predators from different prey types and omnivores from both. Thus, Behmer and Joern (2008) could explain the coexistence of several grasshopper species sharing the same food plants by showing that they had different intake targets, that is, selected different carbohydrate:protein ratios, suggesting they probably feed on different parts of the plants. ...
... The nutritional niche can be seen as an aspect of the Hutchinsonian niche, which is defined as an n-dimensional hypervolume, where the dimensions are environmental conditions and resources that delimit the requirements under which a population is able to persist (Begon et al., 2005). The macronutrient niche is composed of three axes, which are the proportional contents of protein, lipid and carbohydrate of the foods that form the diet of the focal population (Machovsky-Capuska, Senior, et al., 2016). It can be used to characterize the feeding strategy of an animal (Nie et al., 2019). ...
... It can be used to characterize the feeding strategy of an animal (Nie et al., 2019). Thus, predators consume a diet with high content of protein and lipid but low in carbohydrate; herbivores consume a diet high in carbohydrate and protein and usually low in lipid; finally, omnivores consume a diet that mixes considerable amounts of all three macronutrients (Machovsky-Capuska, Senior, et al., 2016). Even if few details are known of the diet's composition of food types, knowledge of the self-selected macronutrient composition may inform us about an animal's position in the community, for example, whether it is a strict carnivore or an omnivore (Nie et al., 2019;Toft, Pavon-Pelaez, et al., 2021). ...
Article
Description of animals’ trophic niches help us understand interactions between species in biological communities that are not easily observed. Analyses of macronutrient niches, i.e. the range of macronutrient (protein:lipid:carbohydrate) ratios selected by generalist feeders, may be a useful alternative approach to inter‐species comparisons of diets, especially within taxonomic assemblages of predators where species with similar nutritional requirements are likely to accept similar types of prey. Here we analysed the macronutritional niches of a woodland assemblage of seven harvestman species, all supposed to be predators with omnivorous tendencies. Five species (Mitopus morio, Leiobunum gracile, Oligolophus tridens, O. hanseni, Paroligolophus agrestis) were native and two species (Opilio canestrinii, Dicranopalpus ramosus) were recent invaders into the community. We compare the fundamental (FMN) and realized (RMN) macronutritional niche positions of the species using a ‘double‐test procedure’, which provides information on whether the species were food limited in their natural habitat, and whether they were limited by specific macronutrients. All seven species were food limited and six species were non‐protein limited in the field; of these, four species were carbohydrate limited, and in one species females were lipid limited and males carbohydrate limited. These findings add to the notion that predators are mainly non‐protein limited in the field. The FMN positions of the assemblage fell within 46‐50% protein, 29‐38% lipid, and 16‐22% carbohydrate. The amount of carbohydrate in the self‐selected diet combined with carbohydrate limitation confirms that the species are zoophytophagous. Two morphological clusters of species (large long‐legged vs. small short‐legged species) differed not only in microhabitat (upper vs. lower forest strata) but also in macronutrient selection, where large long‐legged species selected higher proportion of carbohydrate than small short‐legged species. Thus, morphologically similar species occupy the same habitat stratum and have similar macronutritional niches. We discuss the hypothesis that the invasive O. canestrinii might have an impact on native species as it allegedly had in urban environments previously. Two basic assumptions about interspecific resource competition were fulfilled, i.e. high overlap of nutritional requirements and limitation by food and macronutrients.
... La capacité d'une espèce à exploiter une ressource alimentaire est étroitement dépendante de ses besoins physiologiques, de sa morphologie et ses capacités cognitives (Belovsky, 1986;Costa et al., 2004;Nebel et al., 2005;Reznikova, 2020). La compétition entre les espèces conduit généralement à une spécialisation du régime alimentaire (Colwell, 1973;Smith et al., 2019), bien que les espèces généralistes, qui ont une aptitude plus importante à tirer profit de ressources de nature variées (Machovsky-Capuska et al., 2016), soient avantagées pour s'adapter aux changements saisonniers ou environnementaux (Do Linh San et al., 2020;Rosalino et al., 2005). A l'échelle des individus, les comportements d'alimentation sont influencés par des facteurs intrinsèques (p. ...
... Bien que les contextes environnementaux de ces études soient différents, ces espèces ont tendance à montrer des aptitudes variées à bénéficier des ressources anthropiques. Des différences interspécifiques de phénotype (Felice et al., 2019;Michaud et al., 2020), de physiologie (Hiratsuka and Uehara, 2007;Machovsky-Capuska et al., 2016) ou de comportements (Kent and Sherry, 2020) pourraient expliquer que les espèces ont des capacités différentes à exploiter ou à être compétitives pour certaines ressources. (Herborn et al., 2010). ...
Thesis
Prévenir les risques d’épidémies est devenu un enjeu sanitaire et économique mondial, comme en témoigne l’émergence récente du SARS-COV-2. Cette Thèse vise à améliorer les connaissances sur l’utilisation de l’espace des chauves-souris frugivores (Pteropodidae) dans des environnements modifiés par l’homme. Ce travail mobilise des données de télémétrie satellitaire chez (i) la roussette de Lyle (Pteropus lylei), espèce réservoir du virus Nipah en Asie, et (ii) la chauve-souris à tête de marteau (Hypsignathus monstrosus), impliquée dans la circulation du virus Ebola en Afrique. La population étudiée de roussette de Lyle était déjà connue pour se nourrir préférentiellement dans les zones résidentielles d’un environnement fragmenté au Cambodge. La chauve-souris à tête de marteau, dont l’utilisation des habitats était méconnue, a été étudiée dans une région forestière en République du Congo – épicentre d’épidémies humaine d’Ebola en 2001–2005. De plus, des données de captures directes de chauves-souris ont été collectées dans cette dernière région. Il ressort de ces travaux que la chauve-souris à tête de marteau se nourrit préférentiellement dans les terres agricoles qui entourent les petits villages forestiers. Les individus de roussette de Lyle visitent davantage d’aires d’alimentation dans l’habitat préférentiel durant la nuit, tandis que les chauves-souris à tête de marteau y passent plus de temps sans multiplier le nombre d’aires visitées. Ces deux espèces bénéficient ainsi des ressources anthropiques à l’échelle de la population selon deux stratégies de déplacements individuels, qui sont possiblement ajustées selon le degré de fragmentation de l’environnement. Chez la chauve-souris à tête de marteau, les aires d’alimentation dans la forêt sont délaissées par les individus qui restent longtemps dans le site d’accouplement durant la nuit, ce qui suggère un rôle des terres agricoles dans l’établissement et le maintien des sites d’accouplement. Au cours de nuits successives, les deux espèces revisitent davantage une aire d’alimentation lorsqu’elles y ont passé beaucoup de temps lors de leur dernière visite. Par ailleurs, une communauté de sept espèces de chauves-souris frugivores a été identifiée dans la région étudiée en Afrique. La probabilité d’occurrence de quatre espèces était plus importante dans les villages, tandis que les autres espèces n’étaient pas influencées par l’habitat. L’ensemble de ces travaux fournit de nouvelles informations sur l’utilisation de l’espace des chauves-souris frugivores dans le cadre de leurs activités nocturnes d’alimentation et de reproduction. Ces données pourraient être intégrées dans des modélisations épidémiologiques visant à mieux comprendre les interactions entre les chauves-souris frugivores, les humains ou les animaux domestiques, ainsi que les voies de transmission de pathogènes.
... Proportions-based Nutritional Geometry (PNG, Raubenheimer, 2011) combined with Bayesian multivariate ellipses (Jackson et al., 2011) and the MNNF (Machovsky-Capuska et al., 2016a) were used to explore the three-dimensional relationships between the wet mass proportions of P, L, and W from prey species, diets, and niches of both dolphins and gannets. Following Machovsky-Capuska et al. (2016a), the variety of prey compositions eaten are known as prey composition niche, whereas the diets composed of consuming different prey are known as realized nutritional niches. To estimate the prey composition and realized nutritional niche breadths of dolphins and gannets from proportional data, we combined the MNNF with standard ellipse areas for small sample sizes (SEAc, Syväranta et al., 2013), following Machovsky-Capuska et al. (2018). ...
... Characterising the prey composition and realized nutritional niche breaths, provides novel insights in the degree of generalism of a species (Machovsky-Capuska et al., 2016a and their ability to interact with multiple trophic levels (reviewed in Machovsky-Capuska and Denuncio et al., 2021). At a prey composition level, dolphins showed a broader niche (16.4) comparatively to gannets (6.9), with several non-exclusive explanations available to explain this pattern. ...
Article
Prey detection and subsequent capture is considered a major hypothesis to explain feeding associations between common dolphins and Australasian gannets. However, a current lack of insight on nutritional strategies with respect to foraging behaviours of both species has until now, prevented any detailed understanding of this conspecific relationship. Here we combine stomach content analysis (SCA), nutritional composition of prey, a multidimensional nutritional niche framework (MNNF) and videography to provide a holistic dietary, nutritional, and behavioural assessment of the feeding association between dolphins and gannets in the Hauraki Gulf, New Zealand. Dolphins consumed ten prey species, including grey mullet (Mugil cephalus) as the most representative by wet mass (33.4%). Gannets preyed upon six species, with pilchards (Sardinops pilchardus) contributing most of the diet by wet mass (32.4%) to their diet. Both predators jointly preyed upon pilchard, jack mackerel (Trachurus spp.), arrow squid (genus Nototodarus), and anchovy (Engraulis australis). Accordingly, the MNNF revealed a moderate overlap in the prey composition niche (0.42) and realized nutritional niche (0.52) between dolphins and gannets. This suggests that both predators coexist in a similar nutritional space, while simultaneously reducing interspecific competition and maximizing the success of both encountering and exploiting patchily distributed prey. Behavioural analysis further indicated that dolphin and gannets feeding associations are likely to be mutually beneficial, with a carouselling foraging strategy and larger pod sizes of dolphins, influencing the diving altitude of gannets. Our approach provides a new, more holistic understanding of this iconic foraging relationship, which until now has been poorly understood.
... The N-dimensional quantitative concept of the ecological niche was suggested by Hutchinson (1957); it represents in multidimensional space biotic and abiotic variables that are associated with species occurrence, and provides an opportunity to quantitatively assess niche partitioning among species. Focusing on the resource usage of animals, the Hutchinsonian niche space has been further used to formulate 'multidimensional' isotopic, stoichiometric and nutritional niche concepts, which reflect isotopic composition, elemental composition and nutritional specialisation of organisms, respectively (González et al., 2017;Hutchinson, 1978;Machovsky-Capuska et al., 2016;Newsome et al., 2007). These concepts describe how food choices are correlated with elemental composition of organisms, or nutritional composition of their food. ...
... Such correlations are evident for consumers with contrasting life strategies or communities in contrasting environments (e.g. vertebrates and invertebrates, herbivores and predators, terrestrial and freshwater ecosystems; González et al., 2017) and can be useful to depict the generalist-specialist continuum (Machovsky-Capuska et al., 2016). However, consumers within functional groups share similar physiology and maintain their stoichiometric homeostasis, that is, share similar stoichiometric niches (González et al., 2017). ...
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Trophic niche differentiation may explain coexistence and shape functional roles of species. In complex natural food webs, however, trophic niche parameters depicted by single and isolated methods may simplify the multidimensional nature of consumer trophic niches, which includes feeding processes such as food choice, ingestion, digestion, assimilation and retention. Here we explore the correlation and complementarity of trophic niche parameters tackled by four complementary methodological approaches, i.e., visual gut content‐, digestive enzyme‐, fatty acid‐ and stable isotope analyses – each assessing one or few feeding processes, and demonstrate the power of method combination. Focusing on soil ecosystems, where many omnivore species with cryptic feeding habits co‐exist, we chose Collembola as an example. We compiled fifteen key trophic niche parameters for 125 species from 40 studies. We assessed correlations among trophic niche parameters and described variation of these parameters in different Collembola species, families and across life forms, which represent microhabitat specialisation. Correlation between trophic niche parameters was weak in 45 out of 64 pairwise comparisons, pointing at complementarity of the four methods. Jointly, the results indicated that fungal‐ and plant‐feeding Collembola assimilate storage, rather than structural polysaccharides, and suggested bacterial feeding as a potential alternative feeding strategy. Gut content and fatty acid analyses suggested alignment between ingestion and assimilation/retention processes in fungal‐ and plant‐feeding Collembola. From the fifteen trophic niche parameters, six were related to Collembola family identity, suggesting that not all trophic niche dimensions are phylogenetically structured. Only three parameters were related to the life forms, suggesting that species use various feeding strategies when living in the same microenvironments. Consumers can meet their nutritional needs by varying their food choices, ingestion and digestion strategies, with the connection among different feeding processes being dependent on the consumed resource and consumer adaptations. Multiple methods reveal different dimensions, together drawing a comprehensive picture of the trophic niche. Future studies applying the multidimensional trophic niche approach will allow us to trace trophic complexity and reveal niche partitioning of omnivorous species and their functional roles, especially in cryptic environments such as soils, caves, deep ocean or benthic ecosystems.
... The fundamental niche (i.e., "requirement niche"; Leibold 1995) can be defined as the multivariate space with axes that comprise those parts of an organism's environment that influence its potential to survive and successfully reproduce (i.e., its fitness; Kearney 2006), and thus can be envisioned by the animal's fitness response in relation to a series of niche axes (n-dimensional hypervolume; Hutchinson 1957Hutchinson , 1978. The fundamental nutritional niche consists of niche axes that pertain to nutrients such as protein and carbohydrates (i.e., macronutrient niche; Machovsky-Capuska et al. 2016) and antinutrients such as plant fiber and plant secondary metabolites (PSMs) that influence the value of the nutrients and the animal's ability to acquire them (Van Soest 1982;Robbins 1995). The overlap in food items actually consumed in a particular place and time (i.e., diet composition; the realized dietary niche ;Hutchinson 1957) between herbivore species might not precisely reflect differences in the fundamental nutritional niche that could be used to predict competitive ability and potential use of food resources in sympatry and allopatry. ...
... For example, Behmer and Joern (2008) used an experimental geometric framework to show that seven closely related, co-occurring generalist grasshopper species (Melanoplus spp.) had species-specific macronutrient niches differing in the absolute and relative amount of plant protein and carbohydrates, even though they ate the same plant species. Understanding differences in the fundamental nutritional niche in herbivores therefore requires controlled comparative studies that measure physiological requirements and tolerances as related to fitness for a range of macronutrients (e.g., energy, protein) and antinutrients (e.g., fiber, PSMs) as well as the mechanics of harvesting plants (Kearney 2006;Shipley et al. 2009;Machovsky-Capuska et al. 2016). ...
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Congeneric species often share ecological niche space resulting in competitive interactions that either limit co-occurrence or lead to niche partitioning. Differences in fundamental nutritional niches mediated through character displacement or isolation during evolution are potential mechanisms that could explain overlapping distribution patterns of congenerics. We directly compared nutritional requirements and tolerances that influence the fundamental niche of mule (Odocoileus hemionus) and white-tailed deer (O. virginianus), which occur in allopatry and sympatry in similar realized ecological niches across their ranges in North America. Digestible energy and protein requirements and tolerances for plant fiber and plant secondary metabolites (PSMs) of both deer species were quantified using in vivo digestion and intake tolerance trials with six diets ranging in content of fiber, protein, and PSMs using tractable deer raised under identical conditions in captivity. We found that compared with white-tailed deer, mule deer required 54% less digestible protein and 21% less digestible energy intake per day to maintain body mass and nitrogen balance. In addition, they had higher fiber, energy, and dry matter digestibility and produced glucuronic acid (a byproduct of PSM detoxification) at a slower rate when consuming the monoterpene α-pinene. The mule deers’ enhanced physiological abilities to cope with low-quality, chemically defended forages relative to white-tailed deer might minimize potential competitive interactions in shared landscapes and provide a modest advantage to mule deer in habitats dominated by low-quality forages.
... In nature, animals have evolved strategies to select and ingest foods in order to balance the gain of several nutrients. They balance protein and lipid intake and to meet the specific requirement (Mayntz et al. 2005;Machovsky-Capuska et al. 2016) (!"Nutrient Specific for Aging," Chap. 2). ...
... Under experimental laboratory conditions, high dietary EFA concentrations have an adverse effect on growth and feed efficiency in salmonids (Tacon 1996). The precise amount of lipid required depends on the dietary protein level and, in the cases of omnivores, on the dietary carbohydrate level (Sargent et al. 2002;Machovsky-Capuska et al. 2016). ...
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Lipids are vital. This chapter focuses on recent biomolecular progress in dietary lipid with farmed invertebrates and fishes as well as ecological model organisms. Deficient or excess levels of lipids aggravate disease/pathogen susceptibility; modes of action are sketched and discussed in depth in Chap. 24. First indications point out that different lipid doses trigger different pathways; whether this notion is generalizable remains to be elucidated. The role of lipids as elicitor of biomolecular regulatory pathways of digestion, immunity, and disease resistance is beginning to be understood. First inventories of intestinal microbiota in fishes on different lipidic diets show there might be a potential of probiotic modulation. High-fat diets (HFD) can compromise the immune response by influencing the physical properties of immune cell membranes, membrane-associated signaling molecules, and receptor sites. HFDs combined with high dietary carbohydrates emerge as risky diet, since it upregulates disproportionately large numbers of genes associated with mitochondrial metabolism, neurodegenerative diseases, and liver dysfunction. The involvement of epigenetic pathways in lipid metabolism is beginning to be detected: Dietary fat does not influence growth in a given species but alters hepatic expression of miRNAs and genes related to lipid metabolism causing severe lipid deposition. HFDs induce a fatty liver, which blocks the TCA cycle, disrupts protein and carbohydrate metabolism, and results in reduced growth. Moreover, with “enteroendocrine cells silencing” by HFD via gut microbiota modulation, a new mechanism of nutrient sensing and signaling is detected that might serve as basis for new probiotic HFD treatments.
... We tested the domestication trade-off between yield and vulnerability by performing a study with three objectives. The first was to quantify and visualize the breadth of fundamental nutritional niches (FNNs) 29,31 when fungal cultivars are grown in vitro across artificial nutritional landscapes varying in absolute and [21][22][23]34,35 is restricted to ten representative species co-occurring in Panama). The ants convert this crude forage into nutritional substrates for their fungal cultivars. ...
... b, FNNs 29,31 of fungal cultivars are defined by quantifying their intrinsic tolerances and nutrient requirements after isolating cultivars from ant colonies and rearing them in vitro across substrates varying in concentrations and ratios of protein and carbohydrates (P:C). c, RNNs 29,31 (the macronutrients that ant farmers offer to their cultivars) are defined by sampling and nutritionally analysing substrates collected from the mandibles of returning attine foragers in the field. d, Nutrient provisioning strategies of farmers are assessed by overlaying substrate RNNs atop cultivar FNNs. ...
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During crop domestication, human farmers traded greater productivity for higher crop vulnerability outside specialized cultivation conditions. We found a similar domestication trade-off across the major co-evolutionary transitions in the farming systems of attine ants. First, the fundamental nutritional niches of cultivars narrowed over ~60 million years of naturally selected domestication, and laboratory experiments showed that ant farmers representing subsequent domestication stages strictly regulate protein harvest relative to cultivar fundamental nutritional niches. Second, ants with different farming systems differed in their abilities to harvest the resources that best matched the nutritional needs of their fungal cultivars. This was assessed by quantifying realized nutritional niches from analyses of items collected from the mandibles of laden ant foragers in the field. Third, extensive field collections suggest that among-colony genetic diversity of cultivars in small-scale farms may offer population-wide resilience benefits that species with large-scale farming colonies achieve by more elaborate and demanding practices to cultivate less diverse crops. Our results underscore that naturally selected farming systems have the potential to shed light on nutritional trade-offs that shaped the course of culturally evolved human farming.
... These data would enable the quantitative testing of Charnov's (1976) optimal foraging theory (cf. Zhou et al. 2011b, Thompson & Colgan 1990) and the dietary generalist-specialist distinction within the macronutrient framework (Machovsky-Capuska et al. 2016) with energy-based metrics (Remonti et al. 2016). ...
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[Small Carnivore Conservation: Hisano 2020, Vol. 58, e58009] Examining diet is essential to understanding the ecology and life history of animals. Martens (Martes, Mustelidae: Carnivora) are typical generalist feeders; however, the feeding ecology of Asian martens is less understood compared to those in Europe and North America. On the basis of previous literature reviews, I expose here current gaps in our knowledge of the diet of the Japanese Marten Martes melampus and identify future research requirements. This paper addresses the lack of efforts in measuring food availability and quantifying the Marten diet by biomass/volume metrics, which prevents us from examining optimal foraging theory, a macronutrient framework and interspecific competition with other sympatric carnivores. There are also knowledge gaps in dietary differences between sexes, which could be associated with sexual size dimorphism. Moreover, researchers need to be aware of how environmental changes, including urbanisation and global climate change, may affect the feeding behaviour of the Japanese Marten. Enhancing studies of the Japanese Marten and other Asian Martes species by considering these perspectives will allow us to formulate a comprehensive understanding of adaptive foraging behaviour in Holarctic martens.
... The second critical factor is the dynamic homeostatic responses that animals employ to deal with habitat constraints. These are fundamental because homeostatic limits determine the tolerance ranges (Raubenheimer et al. 2012) and niche breadth (Machovsky-Capuska et al. 2016) of animals. ...
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Both biotic and abiotic factors play important roles in influencing ecological distributions and niche limits. Where biotic and abiotic stressors co‐occur in space and time, homeostatic systems face a scenario in which stressors can compound to impose a challenge that is greater than the sum of the separate factors. We studied the homeostatic strategies of the golden snub‐nosed monkey Rhinopithecus roxellana, a species living in temperate deciduous forests at the edge of the global distribution range for folivorous primates, to cope with the co‐occurrence of cold temperatures and resource scarcity during winter. We discovered that in winter the monkeys experience a dietary energy deficit of 101 kJ mbm−1 d−1 compared with calculated needs, despite increased feeding. This is partly offset by behavioral changes (reduced locomotion and increased resting) and reducing skin temperature by an average of 3.2°C through a cutaneous vasoconstriction to decrease heat loss. However, their major strategy is ingesting surplus energy and accumulating fat reserves when food was not limiting during summer and autumn. Their 14% of body mass lost over the winter represented an energy yield of 102 kJ mbm−1 d−1, which closely matched the calculated winter energy deficit of 101 kJ mbm−1 d−1. However, the latter value assumes that all the 75.41 kJ mbm−1 d−1 of protein ingested in winter was available for energy metabolism. This is almost certainly an over‐estimate, suggesting that the study population was in negative energy balance over the study period. Our study therefore suggests that despite its suit of integrated homeostatic responses, the confluence of low temperatures and resource limitation during winter places this edge‐of‐range primate close the threshold of what is energetically viable. It also provides a framework for quantitative models predicting the vulnerability of temperate primates to global change.
... The Amazonian data do not support the widely held assumption ii that carnivores-herbivores and specialists-generalists have necessarily distinct macronutrient profiles. Thus, a better characterization of the mixture of nutrients in an organism's diet (rather than just the kinds of food or energy content) are necessary to fully understand diet-tissue isotopic fractionations (38,42). Finally, the large range in the e* diet-keratin among Amazonian primary consumers illustrates previously unexpected complexities associated with routing of macronutrients for protein synthesis. ...
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Significance Closed-canopy rainforests are important for climate and ecology, yet identifying this ecosystem in the fossil record is challenging. An existing paradigm for identification of closed-canopy rainforests using fossil mammal carbon isotope data is the presence of highly negative δ ¹³ C diet values (<−31‰) in the herbivore community, as observed in modern equatorial African rainforest ecosystems. Our data from western Amazonian mammals, however, show that the absence of these values is not evidence for absence of closed-canopy rainforests. Our results also document that the proposed relationship between carbon isotope spacing variables and traditional dietary ecological classifications is not straightforward, and that better characterizations of the mixture of nutrients in animal diets are necessary to fully understand diet-tissue isotopic fractionation patterns.
... Consumers with a narrow dietary niche may have a very specialized diet or may utilize a single species or resource for their nutritional needs, while consumers with a broad dietary niche may have a broad range of potential dietary items and display flexibility in foraging ecology [16,17]. While this idea is easy to conceptualize, quantitative measures of niche breadth can be difficult to generate [18]. ...
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Stable isotope data from durable, sequentially-grown tissues (e.g. hair, claw, and baleen) is commonly used for modelling dietary niche breadth. The use of tissues grown over multiple months to years, however, has the potential to complicate isotopic niche breadth modelling, as time‐averaged stable isotope signals from whole tissues may obscure information available from chronologically-resolved stable isotope signals from serially sectioned tissues. We determined if whole samples of brown bear guard hair, a durable, sequentially-grown tissue produced different isotopic niche breadth estimates than those produced from subsampled, serially-sectioned samples of the same tissue from the same set of individuals. We sampled guard hair from brown bears (Ursus arctos) in four regions of Alaska with disparate biogeographies and dietary resource availability. Whole hair and serially-sectioned hair samples were used to produce paired isotopic dietary niche breadth estimates for each region in the SIBER Bayesian modelling framework in R. Isotopic data from serially-sectioned hair consistently produced larger estimates of isotopic dietary niche breadth than isotopic data from whole hair samples. Serial sampling captures finer-scale changes in diet and when cumulatively used to estimate isotopic niche breadth, the serially sampled isotopic data more fully captures dietary variability and true isotopic niche breadth.
... Our understanding of the nutritional niche has been greatly enhanced in recent years through the application of a multidimensional state-space approach, namely the Geometric Framework (GF) for nutrition. The GF was originally developed to disentangle the complex interactions between multiple nutrients and animal performance (reviewed in Simpson and Rauhenheimer 2012) and has been recently expanded to model the multidimensional nutritional niche (Machovsky-Capuska et al. 2016). In this approach, the performance landscape of a relevant parameter that can translate into individual fitness or population persistence is mapped onto the multidimensional macronutrient space where axes are the gradients of macronutrients (e.g., protein, carbohydrate, lipid, etc.). ...
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Temperature and nutrition are amongst the most influential environmental determinants of Darwinian fitness in ectotherms. Since the ongoing climate warming is known to alter nutritional environments encountered by ectotherms, a precise understanding of the integrated effects of these two factors on ectotherm performance is essential for improving the accuracy of predictions regarding how ectotherms will respond to climate warming. Here we employed response surface methodology to examine how multiple life-history traits were expressed across a grid of environmental conditions representing full combinations of six ambient temperatures (13, 18, 23, 28, 31, 33 °C) and eight dietary protein:carbohydrate ratios (P:C = 1:16, 1:8, 1:4, 1:2, 1:1, 2:1, 4:1, 8:1) in Drosophila melanogaster. Different life-history traits were maximized in different regions in the two-dimensional temperature-nutrient space. The optimal temperature and P:C ratio identified for adult lifespan (13 °C and 1:16) were lower than those for early-life female fecundity (28 °C and 4:1). Similar divergence in thermal and nutritional optima was found between body mass at adult emergence (18 °C and P:C 1:1) and the rate of pre-adult development (28 °C and P:C 4:1). Pre-adult survival was maximized over a broad range of temperature (18—28 °C) and P:C ratio (1:8–8:1). These results indicate that the occurrence of life-history trade-offs is regulated by both temperature and dietary P:C ratio. The estimated measure of fitness was maximized at 23 °C and P:C 2:1. Based on the shape of the response surface constructed for this estimated fitness, we characterized the fundamental thermal and nutritional niche for D. melanogaster with unprecedented detail.
... Trophic niche breadth is a cornerstone in ecological theory and knowing the position that individuals, populations and species occupy in the specialist-generalist diet axis is considered essential to understand eco-evolutionary processes from individual fitness and population dynamics to speciation patterns or species distribution 2,20 . In this sense, our study highlights the importance of the nutritional approach for a better understanding of the generalism and specialism concepts as recently advanced 83 . ...
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Optimal foraging theory has typically paid little attention to species feeding on mobile prey and has emphasised energy intake rather than the nutritional contribution of food. The difficulty of capturing food has rarely been included in foraging models, even when it is a potentially important modulator of time devoted to foraging. From the central place foraging and provisioning perspectives, it is posited that at high levels of prey selectivity, the time spent to capture prey is longer than at low levels of prey selectivity. Furthermore, in the case of carnivorous predators, it is thought that nutritional composition does not influence foraging strategies. To explore these issues, we investigated the influence of abundance, size, difficulty of capture, gross energy and nutritional composition (fat, protein, protein-fat ratio and amino acid contents) of prey species on the foraging behaviour of a predator species, the common kestrel Falco tinnunculus, in a region of high diversity of prey species. Our results show that capturability index and load-size explain the foraging behaviour of kestrels. Preferred prey take longer to be provisioned, both selectivity and capturability might explain this result. It is also shown that specific nutritional components, such as protein and amino acid contents, are likely to explain food preference in this carnivorous-insectivorous species.
... Indeed, there are a number of trace elements or macronutrients that may also play important but largely unquantified roles within this system in many species (Costantini, 2008;Machovsky-Capuska, Senior, Simpson, & Raubenheimer, 2016). ...
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1.Physiological processes, including those that disrupt oxidative balance, have been proposed as key to understanding fundamental life history trade‐offs. Yet examination of changes in oxidative balance within wild animals across time, space and major life history challenges remain uncommon. For example, migration presents substantial physiological challenges for individuals, and data on migratory individuals would provide crucial context for exposing the importance of relationships between oxidative balance and fitness outcomes. 2.Here we examined the consistency of commonly used measures of oxidative balance in longitudinally sampled free‐living individuals of a long‐lived, long‐distance migrant, the Brent goose Branta bernicla hrota over periods of months to years. 3.Although inter‐individual and temporal variation in measures of oxidative balance were substantial, we found high consistency in measures of lipid peroxidation and circulating non‐enzymatic antioxidants in longitudinally sampled individuals. This suggests the potential for the existence of individual oxidative phenotypes. 4.Given intra‐individual consistency, we then examined how these physiological measures relate to survival and reproductive success across all sampled individuals. Surprisingly, lower survival was predicted for individuals with lower levels of damage, with no measured physiological metric associated with reproductive success. 5.Our results demonstrate that snapshot measurements of a consistent measure of oxidative balance can inform our understanding of differences in a key demographic trait. However, the positive relationship between oxidative damage and survival emphasises the need to investigate relationships between the oxidative system and fitness outcomes in other species undergoing similar physiologically challenging lifecycles. This would highlight the extent to which variation in such traits and resource allocation trade‐offs is a result of adaptation to different life history strategies.
... Our first hypothesis was that, as in captivity, wild moose regulate the selection and ingestion of food to prioritize a particular balance of nutrients in the rumen content. Multi-dimensional niche theory, a mixture-based approach for examining the nutritional niches of animals, predicts that certain dimensions of the diet will be regulated more strongly than others depending on the evolutionary and ecological circumstances of animals (Machovsky-Capuska et al., 2016). All studies of nutrient balancing in primates to date have demonstrated that the ratio of protein to nonprotein energy (principally nonstructural carbohydrate and lipids) is prioritized by these monogastric herbivores. ...
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At northern latitudes, large spatial and temporal variation in the nutritional composition of available foods poses challenges to wild herbivores trying to satisfy their nutrient requirements. Studies conducted in mostly captive settings have shown that animals from a variety of taxonomic groups deal with this challenge by adjusting the amounts and proportions of available food combinations to achieve a target nutrient balance. In this study, we used proportions‐based nutritional geometry to analyze the nutritional composition of rumen samples collected in winter from 481 moose (Alces alces) in southern Sweden and examine whether free‐ranging moose show comparable patterns of nutrient balancing. Our main hypothesis was that wild moose actively regulate their rumen nutrient composition to offset ecologically imposed variation in the nutritional composition of available foods. To test this, we assessed the macronutritional composition (protein, carbohydrates, and lipids) of rumen contents and commonly eaten foods, including supplementary feed, across populations with contrasting winter diets, spanning an area of approximately 10,000 km2. Our results suggest that moose balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available (and eaten) foods. Furthermore, we found that rumen macronutrient balance was tightly related to ingested levels of dietary fiber (cellulose and hemicellulose), such that the greater the fiber content, the less protein was present in the rumen compared with nonstructural carbohydrates. Our results also suggest that moose benefit from access to a greater variety of trees, shrubs, herbs, and grasses, which provides them with a larger nutritional space to maneuver within. Our findings provide novel theoretical insights into a model species for ungulate nutritional ecology, while also generating data of direct relevance to wildlife and forest management, such as silvicultural or supplementary feeding practices. This right‐angled mixture triangle depicts the relative components of macronutrient content in individual moose (Alces alces) rumen samples. Our results suggest that the 481 moose in our study balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available foods. Furthermore, we found that macronutrient balancing was dependent of rumen fiber content, for this large ruminant herbivore.
... An implication of this latter point is that some of the largest effects of nutrient intake we report will only apply to a small proportion of the population and that our physiology is often robust enough to tolerate relatively wide variation without much consequence. Similar patterns are observed when using the GFN to map evolutionary fitness to organisms that ecologists pre-define as dietary 'generalists' [16,[61][62][63]. This is consistent with an understanding of nutrition in which our ancestors evolved to tolerate an array of dietary patterns [64]. ...
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Background Little is known about how normal variation in dietary patterns in humans affects the ageing process. To date, most analyses of the problem have used a unidimensional paradigm, being concerned with the effects of a single nutrient on a single outcome. Perhaps then, our ability to understand the problem has been complicated by the fact that both nutrition and the physiology of ageing are highly complex and multidimensional, involving a high number of functional interactions. Here we apply the multidimensional geometric framework for nutrition to data on biological ageing from 1560 older adults followed over four years to assess on a large-scale how nutrient intake associates with the ageing process. Results Ageing and age-related loss of homeostasis (physiological dysregulation) were quantified via the integration of blood biomarkers. The effects of diet were modelled using the geometric framework for nutrition, applied to macronutrients and 19 micronutrients/nutrient subclasses. We observed four broad patterns: (1) The optimal level of nutrient intake was dependent on the ageing metric used. Elevated protein intake improved/depressed some ageing parameters, whereas elevated carbohydrate levels improved/depressed others; (2) There were non-linearities where intermediate levels of nutrients performed well for many outcomes (i.e. arguing against a simple more/less is better perspective); (3) There is broad tolerance for nutrient intake patterns that don’t deviate too much from norms (‘homeostatic plateaus’). (4) Optimal levels of one nutrient often depend on levels of another (e.g. vitamin E and vitamin C). Simpler linear/univariate analytical approaches are insufficient to capture such associations. We present an interactive tool to explore the results in the high-dimensional nutritional space. Conclusion Using multidimensional modelling techniques to test the effects of nutrient intake on physiological dysregulation in an aged population, we identified key patterns of specific nutrients associated with minimal biological ageing. Our approach presents a roadmap for future studies to explore the full complexity of the nutrition-ageing landscape.
... Third, insects are seldom limited by a single nutrient at a time, and the value of a given plant resource thus depends on ratios and concentrations of multiple interacting nutrients (Simpson & Raubenheimer, 2012). Nutritional geometry (NG) has provided new approaches for studying these multidimensional dietary challenges (Machovsky-Capuska et al., 2016;Shik & Dussutour, 2020) and has shown that organisms have diverse strategies for prioritising specific nutrients when foraging for and consuming imbalanced foods (Dussutour et al., 2010;Lee et al., 2008). We applied NG approaches to study nutritional regulation strategies in free-ranging colonies of the leafcutter ant Atta colombica. ...
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Foraging trails of leafcutter colonies are iconic scenes in the Neotropics, with ants collecting freshly cut plant fragments to provision a fungal food crop. We hypothesised that the fungus‐cultivar's requirements for macronutrients and minerals govern the foraging niche breadth of Atta colombica leafcutter ants. Analyses of plant fragments carried by foragers showed how nutrients from fruits, flowers and leaves combine to maximise cultivar performance. While the most commonly foraged leaves delivered excess protein relative to the cultivar's needs, in vitro experiments showed that the minerals P, Al and Fe may expand the leafcutter foraging niche by enhancing the cultivar's tolerance to protein‐biased substrates. A suite of other minerals reduces cultivar performance in ways that may render plant fragments with optimal macronutrient blends unsuitable for provisioning. Our approach highlights how the nutritional challenges of provisioning a mutualist can govern the multidimensional realised niche available to a generalist insect herbivore. Free‐ranging leafcutter ants forage nutritionally and chemically diverse plant fragments to fit the requirements of their fungal food crop. However, these foraged plant fragments can also contain nutrients in excess of the cultivar's tolerance, which can limit fungal production. Results obtained from in vitro cultures suggest that the mineral composition of plant fragments might influence the suitability of the nutrient blends provided to the fungal culture, thus allowing the cultivar to exploit apparently toxic blends of nutrients.
... ticks or mosquitoes), then its host specificity mainly reflects the nutritional dimension of its niche, including the range of nutrients this parasite can utilize (dependent on physiological abilities and constraints) and the patterns of acquiring these resources (e.g. foraging behaviour) (Machovsky-Capuska et al. 2016). If, however, a host provides a parasite not only with food resources but also with a living, mating, and reproduction place (i.e. a parasite's habitat), then host specificity represents multiple dimensions of a parasite's niche. ...
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We applied the concept of dark diversity (species that may potentially inhabit a locality but are absent) to the host spectrum of a parasite and defined it as dark host specificity (DHS). We studied the trait-associated and geographic patterns of dark host specificity in fleas and gamasid mites parasitic on small mammals, asking the following questions: (a) Is dark host specificity repeatable across populations of the same species? (b) Is it associated with morphological and/or ecological species traits? (c) What are the factors associated with geographical variation in the DHS among populations of the same species? The DHS was repeatable within species with a large proportion of variance among samples, accounted for by differences between species. The average DHS of fleas, but not mites, was affected by parasite traits, with the DHS being higher in fleas with larger geographic ranges, higher characteristic abundance levels, and summer reproduction peaks. In the majority of ectoparasites, the regional DHS decreased with an increase in either structural or phylogenetic host specificity. The associations between the DHS and the environmental or host-associated characteristics of a region were revealed in a few species (eight of 22 fleas and three of 12 mites). The DHS decreased with (a) an increase in air temperature in two fleas, (b) a decrease in precipitation in two fleas, and (c) an increase in regional host species richness (in three fleas and three mites). Overall, our results suggest that dark host specificity in arthropod ectoparasites is a species-specific character associated, to a large extent, with the breadth of their host-related niches, while the influences of parasite traits and local environmental conditions are minor.
... An individual with a generalist feeding behaviour will have a broad, more or less diverse, food spectrum, depending on seasonal needs and environmental opportunities. Specialist predators, on the other hand, will have a narrower food spectrum and are generally considered as more vulnerable (Machovsky-Capuska et al., 2016). Therefore, specialists are more prone to extinction, while generalists are assumed to be more resilient, having a greater capacity of adaptation and dispersion, and thus becoming more easily invasive. ...
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Next-generation sequencing is increasingly used in conservation biology to resolve complex interactions between species, either diet or gut parasites studies. We applied a recent long metabarcoding method to elucidate the green whip snake’s (Hierophis viridiflavus) prey consumption based on DNA extracted from stomach contents. Illegally introduced in Canton of Vaud (Switzerland), three populations of the green whip snake have strongly developed in two regions, East (Chablais) and North. We suspect that this introduced species is threatening part of the local herpetofauna, especially the Asp viper and the Western green lizard in this region. Consequently, an extermination program has been implemented from 2016 to mitigate Hierophis viridiflavus expansion and its impact arising from its generalist diet. Stomach contents of 94 individuals removed from introduction sites were analysed by long metabarcoding. Our study revealed the consumption of 67 prey belonging to 9 species, primarily small mammals and reptiles. The recurrent presence of two parasitic nematodes was also discovered. Although cannibalistic behaviour could not be highlighted with this approach, a scavenging behaviour was suspected based on the presence of an insect used in forensic entomology (Calliphora vicina). These results confirm the opportunistic feeding behaviour of Hierophis viridiflavus and its ability to predate on threatened species. Although 86.6% of preys were not listed on the Swiss Red List, the impact on the Asp viper population can be important (up to 20% of consumed preys) and could partially explain its strong decline.
... Although both the pine marten and stone marten can consume a large variety of food items, their trophic niches overlap largely (Remonti et al., 2012;Zalewski, 2004). Local and seasonal variations in food availability make it difficult to compare the diets of generalist species, an impediment that can be overcome by integrating the traditional approach of evaluating dietary niches in terms of foods alone with their macronutrient composition (Machovsky-Capuska et al., 2016). Both laboratory and field studies have demonstrated that animals can self-select species-specific ratios of macronutrients-protein, lipids, and carbohydrates (Balestrieri et al., 2019;Raubenheimer & Simpson, 1997), and macronutrient intakes can be used to effectively compare the diets of generalist predators (Gazzola & Balestrieri, 2020). ...
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The macronutrient requirements of the strictly related pine marten (Martes martes) and stone marten (Martes foina) are almost identical, but, at range scale, in areas of putative sympatry (overlapping European ranges) the stone marten tends to be more frugivorous, which makes the contribution of carbohydrate energy to be higher than the target. In contrast, the macronutrient intake of the pine marten would be unaffected by the occurrence of the stone marten, supporting the putative dominance of the first in interspecific interactions. Most available studies examined marten diets separately, highlighting the need for further studies in areas of actual co-occurrence. With this aim, we compared the two martens' diets in the Italian Alps both in sympatric and allo-patric conditions, as assessed by the genetic identification of scats. Although fruit and rodents formed the bulk of both species' diets, as predicted the stone marten consumed twice as many fruit species as the pine marten and ate fruit more often in areas of sympatry, thus consuming less protein and more carbohydrates respect to its intake target. This competition-driven, nutritionally imbalanced diet may affect the fitness of stone marten populations and play an important and still underreported role in regulating the relative abundance of marten communities. K E Y W O R D S allopatry, competition, diet, macronutrient ratio, sympatry
... Recent work on consumer nutrition has emphasized tracing macronutrients (e.g., carbohydrates, lipids, and protein) because it is an intuitive approach to diet estimation and potentially offers insight into resource use constraints related to meeting competing physiological demands (e.g., maintenance, growth, storage, reproduction; Coogan et al. 2014;Machovsky-Capuska et al. 2016;Machovsky-Capuska and Raubenheimer 2020). The most widely used macronutrient tracers include stable isotopes (Martínez del Rio et al. 2009;Boecklen et al. 2011) and fatty acids (Budge and Iverson 2006;Bowen and Iverson 2013), which occasionally have been used in tandem (O'Donovan et al. 2018) and are often the only available diet estimation tools for free-ranging animals that integrate nutritional history over weeks to months Scherer et al. 2015). ...
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Free-ranging predator diet estimation is commonly achieved by applying molecular-based tracers because direct observation is not logistically feasible or robust. However, tracers typically do not represent all dietary macronutrients, which likely obscures resource use as prey proximate composition varies and tissue consumption can be specific. For example, polar bears (Ursus maritimus) preferentially consume blubber, yet diets have been estimated using fatty acids based on prey blubber or stable isotopes of lipid-extracted prey muscle, neither of which represent both protein and lipid macronutrient contributions. Further, additional bias can be introduced because dietary fat is known to be flexibly routed beyond short-term energy production and storage. We address this problem by simultaneously accounting for protein and lipid assimilation using carbon and nitrogen isotope compositions of lipid-containing prey muscle and blubber to infer summer/fall diet composition and macronutrient proportions from Chukchi Sea polar bear guard hair (n = 229) sampled each spring between 2008 and 2017. Inclusion of blubber (85–95% lipid by dry mass) expanded the isotope mixing space and improved separation among prey species. Ice-associated seals, including nutritionally dependent pups, were the primary prey in summer/fall diets with lower contributions by Pacific walruses (Odobenus rosmarus) and whales. Percent blubber estimates confirmed preferential selection of this tissue and represented the highest documented lipid assimilation for any animal species. Our results offer an improved understanding of summer/fall prey macronutrient usage by Chukchi Sea polar bears which likely coincides with a nutritional bottleneck as the sea ice minimum is approached.
... Diet quality, in terms of both the quantity and ratio of nutrients, is a key factor shaping the expression of functional traits in many animal species (Machovsky-Capuska et al., 2016;Malod et al., 2017;. Traits include morphological, physiological, phenological or behavioural characteristics that, when related to the performance of an organism, are referred to as functional traits (Brousseau et al., 2018). ...
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... Alternatively, D. setosum may prefer hard substrates in order to avoid its potential predators by hiding between rocks and small crevices (Coppard & Campbell, 2005;Dumas et al., 2007;reviewed in Muthiga & McClanahan, 2007); however, no predator for this echinoid species in the Mediterranean Sea has been reported. Furthermore, various feeding preferences of D. setosum have previously been reported mostly from its native habitats (Coppard & Campbell, 2005;Luza & Malay, 2019); however, echinoid species can consume a variety of diet items (Coppard & Campbell, 2005), which is a common dietary trait for the successful invasive species (Slatyer et al., 2013;Machovsky-Capuska et al., 2016). Moreover, Diadema species consume an important portion of sand in order to obtain biofilm and particulate organic matter accumulate on the sand surface (Muthiga & McClanahan, 2007). ...
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Sea urchins are important members of benthic communities by impacting algal production and therefore the other members of the communities. A member of these organisms, Diadema setosum Leske, 1778, was introduced to Mediterranean Sea in 2006 and it has extended its distribution to various localities. However, previous studies on this invasive species have only focused on its occurrences in different parts of the Mediterranean Sea. Here, we conducted an observational study on the density of this sea urchin at six sites along the Turkish coast of Aegean Sea differing in the habitat types. Additionally, we determined the density of a native sea urchin, Arbacia lixula Linnaeus 1758, at the same sites to reveal the potential interactions between these two species. We found that D. setosum reached a notable density on the Turkish coast of Aegean Sea and this density was higher at the sites with hard bottoms. We further found an inverse relationship between the densities of D. setosum and of A. lixula. Overall, this study emphasizes the need of an urgent management/conservation plan since D. setosum has already reached the previously reported threshold density at which it is harmful to benthic communities in the Mediterranean Sea.
... In recent years, the field of nutritional geometry (NG) has provided a research agenda and an empirical toolbox for rigorously testing these nutritional ecology hypotheses that naturally encompass multiple niche dimensions . One recent NG innovation allows researchers to seamlessly integrate results of controlled laboratory-based experiments and field-based approaches in fluctuating environments (Machovsky-Capuska, Senior, et al., 2016;Raubenheimer, 2011;Shik & Dussutour, 2020). First, we can define a consumer's fundamental nutritional niche (FNN) by measuring performance when the organism is confined to a suite of nutritionally defined diets in the laboratory (Lee et al., 2008;Shik et al., 2016). ...
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The biochemical heterogeneity of food items often yields tradeoffs as each bite of food tends to contain some nutrients in surplus and others in deficit, as well as other less palatable or even toxic compounds. These multidimensional nutritional challenges are likely compounded when foraged foods are used to provision others (e.g. offspring or symbionts) with different physiological needs and tolerances. We explored these challenges in free‐ranging colonies of leafcutter ants that navigate a diverse tropical forest to collect plant fragments they use to provision a co‐evolved fungal cultivar. We tested the prediction that leafcutter farmers face provisioning tradeoffs between the nutritional quality and concentration of toxic tannins in foraged plant fragments. Chemical analyses of plant fragments sampled from the mandibles of Panamanian Atta colombica leafcutter ants provided little support for a nutrient–tannin foraging tradeoff. First, colonies foraged for plant fragments ranging widely in tannin concentration. Second, high tannin levels did not appear to restrict colonies from selecting plant fragments with blends of protein and carbohydrates that maximized cultivar performance when measured with in vitro experiments. We also tested whether tannins expand the realized nutritional niche selected by leafcutter ants into high‐protein dimensions since: 1) tannins can bind proteins and reduce their accessibility during digestion, and 2) in vitro experiments have shown that excess protein provisioning reduces cultivar performance. Contrary to this hypothesis, the most protein‐rich plant fragments did not have highest tannin levels. More generally, the approach developed here can be used to test how multidimensional interactions between nutrients and toxins shape the costs and benefits of providing care to offspring or symbionts.
... Therefore, they cannot be fastidious; instead, they have to accept suboptimal food compositions with lower shares of proteins and higher shares of lipids or, particularly, carbohydrates, if algae or macrophytes are the main food sources. However, in the medium to long term, animals have to balance their needs in macronutrients (Machovsky-Capuska et al. 2016;Machovsky-Capuska and Raubenheimer 2020). In other words, since almost all animals in the wild have to face periods of suboptimal food quality, protein sparing by lipids or carbohydrates should be a common, at least temporary, strategy in aquatic animals, if they have the eventual chance to balance their nutrient demands. ...
Chapter
Mainly based on economical and ethical considerations, proteins are intended to be replaced by cheaper and ethically less critical macronutrients. This chapter summarizes recent papers dealing with protein and carbohydrate replacement by dietary lipids. It becomes obvious that replacement successes are evaluated one-dimensionally by production traits, such as growth performance, flesh quality, health, and pathogen resistance, and, with respect to brood stock, reproductive performance rather than ecological nutritional criteria. In particular, the capacity of aquatic animals to balance their macronutrient intake deserves attention, even under farmed conditions. Emerging studies point out the paramount importance of the axis intestinal microbiota-host welfare in lipid metabolism: Lipid diets modulate the intestinal microflora, and, vice versa, by adding appropriate probiotics, increased dietary lipid can be tolerated.
... Nutrient contents and secondary metabolites of host plants contribute to the nutritional performance, growth, development, and reproduction of insect pests (Awmack and Leather, 2002;Machovsky-Capuska et al., 2016). Plant's secondary metabolites, such as phenols, terpenes, and nitrogen-containing compounds, can exhibit toxic, repellent or antifeedant effects on insect pests (Beck, 1965;Horber, 1980;Bernays and Chapman, 1994). ...
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Spodoptera littoralis (Boisd) is globally recognized as a destructive polyphagous insect pest of various crops in the world. It is commonly managed by chemical pesticides, which can cause deleterious effects such as environmental pollution, toxicity to non-target organisms and the emergence of secondary pests. Hence, investigations into alternative pest control strategies such as the use of resistant host plant cultivar against S. littoralis is important. This study aimed to explore the nutritional performance of S. littoralis larvae in dependence on total anthocyanin, flavonoid, and phenol levels across 11 bean cultivars ( Phaseolus and Vigna spp.) under laboratory conditions. The results revealed that the Mashhad cultivar accumulated the highest amount of total phenols (13.59 mg ml ⁻¹ ), whereas Yaghout and Arabi cultivars posed the lowest total phenols contents (1.80 and 1.90 mg ml ⁻¹ , respectively). Across larval instars (third to sixth), the highest consumption index and relative consumption rate were recorded on the Mashhad cultivar. The lowest values of efficiency of conversion of ingested food and the efficiency of conversion of digested food of total larval instars were detected in the larvae which were reared on the Mashhad cultivar. Likewise, the lowest value of the index of plant quality (IPQ) was obtained in the Mashhad cultivar; however, IPQ was figured out at the highest level in the Arabi cultivar. Our findings show that the differential accumulation of secondary metabolites would change the nutritional quality of plants for S. littoralis . Based on the findings, the Mashhad cultivar may serve as a candidate for either integrated pest management or breeding programs aiming at controlling this pest.
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Foraging in uncertain environments requires balancing the risks associated with finding alternative resources against potential gains. In arid-land environments characterized by extreme variation in the amount and seasonal timing of primary production, consumers must weigh the risks associated with foraging for preferred seeds that can be cached against fallback foods of low nutritional quality (e.g., leaves) that must be consumed immediately. Here, we explore the influence of resource scarcity, body size, and seasonal uncertainty on the expected foraging behaviors of caching rodents in the northern Chihuahaun Desert by integrating these elements with a stochastic dynamic program to determine fitness-maximizing foraging strategies. We demonstrate that resource-limited environments promote dependence on fallback foods, reducing the likelihood of starvation while increasing future risk exposure. Our results point to a qualitative difference in the use of fallback foods and the fitness benefits of caching at the threshold body size of 50 g. Above this 50-g body size threshold, we observe large fitness gains associated with the maintenance of even a modest-sized cache, whereas similar gains for smaller consumers require maintenance of unrealistically large caches. This suggests that larger-bodied consumers that cache may be less sensitive to the future uncertainties in monsoonal onset predicted by global climate scenarios, whereas smaller consumers, regardless of caching behavior, may be at greater risk.
Chapter
The global rise in the incidence of obesity and associated non-communicable chronic diseases has far outstripped the ability to understand and manage the causes. We introduce a field from the natural sciences, called nutritional ecology, which we believe can contribute toward unraveling the causes of and identifying key control points for managing the growing epidemic of chronic disease. We begin by clarifying how we use the term “nutritional ecology” to place it in the context of related terms, emphasizing that ours is a biologically inspired approach that can help to structure nutrition research by introducing into nutrition science theory and methods from ecological and evolutionary sciences. We then discuss some biological insights from nutritional ecology that we suggest can make a significant contribution to nutrition research and clinical practice and thereafter introduce a geometric framework for implementing this theory. We end with examples showing that the implementation of biological thinking via nutritional geometry can provide a concrete step toward understanding how human biology interacts with our radically altered industrialized food environments to generate health and disease.
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Humans are translocating species beyond their native ranges increasingly fast. These translocations create a natural experiment to explore the role of cognition in invasiveness. Alien vertebrate species face many behavioral challenges upon introduction to novel environments. But here, we focus on how alien species might use cognition to find and adopt new foods. Cognitive processes are particularly well suited to this challenge, a prediction supported by large-scale comparative analyses of alien species’ historical introductions. Here, we parse the steps involved in approaching, handling, tasting, and evaluating novel food sources and, for each one, describe which cognitive abilities are the most relevant. In bringing attention to the functional importance of innovative feeding both conceptually and empirically, synthesizing the cognitive processes involved, highlighting the current void of knowledge, and arguing that alien species are particularly well suited to controlled experimental cognitive studies, this piece scaffolds future experimental cognitive research.
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Diets of species are crucial in determining how they influence food webs and community structures, and how their populations are regulated by different bottom‐up processes. Omnivores are able to adjust their diet flexibly according to environmental conditions, such that their impacts on food webs and communities, and the macronutrients constraining their population, can be plastic. In particular, omnivore diets are known to be influenced by prey availability, which exhibit high spatial and temporal variation. To examine the plasticity of diet and macronutrient limitation in omnivores, we compared trophic positions, macronutrient preferences and food exploitation rates of omnivorous ants in invertebrate‐rich (secondary forests) and invertebrate‐poor (Lophostemon confertus plantations) habitats. We hypothesized that omnivorous ants would have lower trophic positions, enhanced protein‐limitation and reduced food exploitation rates in L. confertus plantations relative to secondary forests. We performed cafeteria experiments to examine changes in macronutrient limitation and food exploitation rates. We also sampled ants and conducted stable isotope analyses to investigate dietary shifts between these habitats. We found that conspecific ants were less carnivorous and had higher preferences for protein‐rich food in L. confertus plantations compared to secondary forests. However, ant assemblages did not exhibit increased preferences for protein‐rich food in L. confertus plantations. At the species‐level, food exploitation rates varied idiosyncratically between habitats. At the assemblage‐level, food exploitation rates were reduced in L. confertus plantations. Our results reveal that plantation establishments alter the diet and foraging behavior of omnivorous ants. Such changes suggest that omnivorous ants in plantations will have reduced top‐down impacts on prey communities but also see an increased importance of protein as a bottom‐up force in constraining omnivore population sizes.
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The trophic niche of an organism is tightly related to its role in the ecosystem and to interactions with other species. Thousands of species of soil animals feed on detritus and co-exist with apparently low specialisation in food resource use. Trophic niche differentiation may explain species coexistence in such a cryptic environment. However, most of the existing studies provide only few and isolated evidence on food resources, thus simplifying the multidimensional nature of the trophic niches available in soil. Focusing on one of the most diverse soil taxa – springtails (Collembola) – we aimed to reveal the additional value of information provided by four complementary methods: visual gut content-, digestive enzyme-, fatty acid- and stable isotope analyses, and to demonstrate the multidimensional nature of trophic niches. From 40 studies, we compiled fifteen key trophic niche parameters for 125 species, each analysed with at least one method. Focusing on interspecific variability, we explored correlations of trophic niche parameters and described variation of these parameters in different Collembola species, taxonomic groups and life forms. Correlation between trophic niche parameters of different methods was weak in 45 out of 64 pairwise comparisons, reflecting the complementarity of the multidimensional trophic niche approach. Gut content and fatty acids provided comparable information on fungivory and plant feeding in Collembola. Information provided by digestive enzymes differed from that gained by the other methods, suggesting its high additional value. Stable isotopes were mainly related to plant versus microbial feeding. Many parameters were affected by taxonomic affiliation but not life form. Furthermore, we showed evidence of bacterial feeding, which may be more common in Collembola than usually assumed. Different methods reveal different feeding dimensions, together drawing a comprehensive picture of the trophic niche in taxa with diverse feeding habits. Food web studies will benefit from simultaneously applying several joint approaches, allowing to trace trophic complexity. Future studies on the multidimensional trophic niche may improve understanding of food-web functioning and help to explain species coexistence in cryptic environments such as soil.
Chapter
Proteins represent the dominant biomass of aquatic animals; consequently, proteins are significant nutrients and energy sources with digestive efficiencies between 60 and almost 100%. For most aquatic animals, the quantity of prey available is typically the nutritional bottleneck. A deficiency of dietary protein or amino acids has long been known to impair immune function and increase the susceptibility of animals to infectious disease. In addition to function as energy source, free amino acids can act as osmolytes. The average dietary protein requirement of fishes is 42%; that of invertebrates appears to be below this value. Protein requirement depends on environmental factors, such as salinity and temperature, as well as trophic level and content of the other macronutrients. Interactions with other macronutrients, however, are not yet adequately considered. Adverse effects occur in animals fed deficient or excess proteinaceous diets. Biomolecular modes of action of hyperproteic diets are beginning to be understood; impairment of the immune system is central. Finally, this chapter points out gaps of protein nutrition in aquatic animals.
Chapter
This introductory chapter to organic macro- and micronutrients in aquatic animal nutrition points out recent highlights in identifying nutrient-triggered pathways. It stresses that, in the entire book, particular emphasis will put on the differentiation between esoteric and innovative research in the Kuhnian sense. Innovative research in aquatic animal nutrition has to go beyond production performance and consider aquatic animals as entire, individual ecosystems with complex controlling pathways, in which host-microbiota interactions are central. Therefore, this introduction eventually refers to the classical superorganism concept as guiding principle, recently specified to fishes as hologenomics concept.
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The nutritional characteristics of food resources play an important role in the foraging behavior of animals and can provide information valuable to their conservation and management. We examined the nutritional ecology of wild water buffalo (Bubalus arnee ; hereafter “buffalo”) in the Koshi Tappu Wildlife Reserve of Nepal during autumn using a multidimensional nutritional niche framework. We identified 54 plant species as being foraged by buffalo. We found that buffalo consumed graminoids and forbs 2–3 times more frequently than browse items. Proximate analyses of the 16 most frequently foraged plants indicated that buffalo diets were highest in carbohydrate (40.41% ± 1.82%) followed by crude protein (10.52% ± 0.93%) and crude fat (1.68% ± 0.23%). The estimated macronutrient balance (i.e., realized nutrient niche) of the buffalo diet (20.5% protein: 72.8% carbohydrate: 6.7% lipid) was not significantly different than the average balance of all analyzed food items based on 95% confidence regions. Our study suggests that buffalo are likely macronutrient specialists, yet may be generalists in the sense that they feed on a wide range of food items to achieve a nutrient balance similar to that available in forage items. However, the four most frequently consumed items tended to be higher in protein energy than less frequently consumed foods, suggesting some preference for higher protein forage relative to relatively abundant carbohydrates. Although limited in scope, our study provides important information on the nutritional ecology of buffalo, which may be useful for the conservation and management of this endangered species.
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1. In ecological niche theory, diet is a trait frequently used to place species along a continuum from specialists to generalists. A multidimensional approach to investigating species' niches has been developed to incorporate nutrition. We apply the concepts of multidimensional nutritional niche theory to the dietary patterns of a widespread, large herbivore, the American bison Bison bison, at various levels of its nutritional niche. 2. Specifically, we sought to estimate dietary niches for female bison at the levels of the forage items they consume and the macronutrients they acquire from those forage items. We assessed how these dietary niches changed seasonally and explored physical and climatic mechanisms that contribute to observed differences in the dietary niches. We also examined dietary differences between the two bison subspecies: wood bison Bison bison athabascae and plains bison Bison bison bison. 3. We compiled data for 16 bison subpopulations using 26 peer-reviewed publications , government reports, conference proceedings, and graduate theses that described the dietary composition of female bison for analysis of dietary niches. 4. We found that the diets of female bison were, as expected, dominated by graminoids throughout the year, but during the growing season (spring and summer), dietary niches had greater breadth. Their diets were relatively high in carbohydrates, but percentages of dietary lipid and protein increased during the growing season. Further, we found significant increases in consumption of browse items, lipids, and proteins with increasing latitude (°N), and differences between American bison subspecies. 5. Our study provides insight into the fundamental macronutrient niche of the American bison and also provides a framework for the nutritional targets of bison. We show that bison are able to adapt to availability of local forage and that they may consume different items in different proportions in order to regulate nutritional composition of their diet.
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The red fox (Vulpes vulpes) is the world's most widespread member of the order Carnivora, occurring across a large range of latitudes and inhabiting multiple habitat types. There is no comprehensive study of how the diets of this flexible generalist vary across the whole Asian continent. We conducted a meta-analysis of red fox diets in Japan, examining the patterns in food type selection and their associations with seasonality, regional climate, vegetation productivity, and human influences at the national scale. Using linear mixed models, we revealed significant seasonal effects on the frequency of occurrence of mammals in general, ungulate carcasses, birds, and invertebrates in the diets of red foxes. Furthermore, the frequency of occurrence of mammals significantly decreased with mean annual temperature and increased with vegetation productivity. The frequency of invertebrate occurrences increased with temperature, and that of anthropogenic foods increased with human population density. Trophic diversity and dietary niche breadth increased with annual temperature but decreased with vegetation productivity and population density. These results suggest that the red fox is a flexible predator in Japan that adapts its foraging patterns according to variations in resource availability and abiotic conditions, while persistently consuming a certain ratio of animal prey to meet its metabolic requirements. Modifications of predators' trophic niches can influence structures of prey communities and interactions with sympatric competitors. Our findings are important for informing ecosystem management practices under ongoing environmental and social changes in Japan. © 2021 The Authors. Ecological Research published by John Wiley & Sons Australia, Ltd on behalf of The Ecological Society of Japan.
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Apposite conceptualization and measurement of resource variation is critical for understanding many issues in ecology, including ecological niches, persistence and distribution of populations, the structure of communities, and population resilience to perturbations. We apply the nutritional geometry framework to conceptualise and quantify the responses of a temperate‐living primate, the golden snub‐nosed monkey (Rhinopithecus roxellana) to variation in resource quality and quantity and in nutrient requirements associated with seasonal environments. We present a geometric model distinguishing qualitative constraint, quantitative constraint, and “pseudo‐constraint” whereby nutrient intakes resemble response to qualitative resource constraint but are in fact driven by variation in nutrient requirements. The model is applied to analyse nutrient intakes recorded in 164 full day observations of monkeys from two populations, one wild and the other captive, across seasons. Additionally, we recorded the diet of a single animal over 32 consecutive days in the wild. Despite considerable differences in available resources, the captive and wild populations showed marked similarities in nutrient intakes, including indistinguishable amounts and ratios of ingested macronutrients during summer and autumn and strong year‐round maintenance of protein compared to seasonally variable fat and carbohydrate intakes. These similarities suggest homeostatically regulated nutritional targets and provide reference points to identify factors driving population differences in macronutrient intake in winter and spring. Our framework enabled us to distinguish examples of quantitative, qualitative, and “pseudo‐constraint”. We suggest that this approach can increase the resolution at which resource constraint is conceptualised and measured in ecological studies.
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Nitrogen and phosphorus are thought to be the most important limiting nutrients in most terrestrial ecosystems, but little is known about how other elements may limit the abundance of arthropods. We utilized a fully factorial fertilization experiment that manipulated macronutrients (N&P, together) and micronutrients (calcium, sodium, potassium, separately), in large 30 x 30 m2 plots and sampled litter arthropods via pitfall trapping to determine the nutrients that limit this group. An invasive ant, Nylanderia fulva, numerically dominated the community and increased in abundance 13% in plots fertilized by Ca. Detritivores were not limited by any nutrient combination, but macronutrients increased predator abundance 43%. We also found that some combinations of macronutrients and micronutrients had toxic or stressful effects on the arthropod community: detritivores decreased in abundance 23% with the combination of macronutrients, Ca, and K, and 22% with macronutrients and K; and N. fulva decreased in abundance 24% in plots fertilized by K and 45% in plots fertilized by the combination of Na and K. Our work supports growing evidence that micronutrients, especially Ca and K, may be important in structuring grassland arthropod communities, and suggests that micronutrients may affect whether or not invasive ants reach numerical dominance.
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Mismatch is a prominent concept in evolutionary medicine and a number of philosophers have published analyses of this concept. The word ‘mismatch’ has been used in a diversity of ways across a range of sciences, leading these authors to regard it as a vague concept in need of philosophical clarification. Here, in contrast, we concentrate on the use of mismatch in modelling and experimentation in evolutionary medicine. This reveals a rigorous theory of mismatch within which the term ‘mismatch’ is indeed used in several ways, not because it is ill-defined but because different forms of mismatch are.distinguished within the theory. Contemporary evolutionary medicine has unified the idea of ‘evolutionary mismatch’, derived from the older idea of ‘adaptive lag’ in evolution, with ideas about mismatch in development and physiology derived from the Developmental Origins of Health and Disease (DOHaD) paradigm. A number of publications in evolutionary medicine have tried to make this theoretical framework explicit. We build on these to present the theory in as simple and general a form as possible. We introduce terminology, largely drawn from the existing literature, to distinguish the different forms of mismatch. This integrative theory of mismatch captures how organisms track environments across space and time on multiple scales in order to maintain an adaptive match to the environment, and how failures of adaptive tracking lead to disease. Mismatch is a productive organising concept within this theory which helps researchers articulate how physiology, development and evolution interact with one another and with environmental change to explain health outcomes.
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Food supply is one of the major drivers of animal behaviour and the gut microbiome is an important mediator between food supply and its effects on physiology. However, predicting the outcome of diet change on microbiome and consequences for the animal has proven extremely challenging. We propose this reflects processes occurring at different scales. Inadequate accounting for the multi-level complexity of nutrition (nutrients, foods, diets) obscures the diet influence on microbiome and subsequently animal. Here we present a detailed year-round, multi-level analysis of diet and microbiome changes in a wild population of a temperate primate, the rhesus macaque (Macaca mulatta). Total daily food and nutrient intake of six male and six female macaques was monitored in each the four seasons (total 120 days observations). For each individual we found significant variation in the microbiome between all four seasons. This response was more strongly correlated with changes in macronutrient intake than with food items and much of the response could be explained at the level of six ecological guilds – sets of taxa sharing similar responses to nutrient intake. We conclude that study of diet, microbiome and animal performance in ecology will more effectively identify patterns if diet is recorded at the level of nutrient intake. Although microbiome response to diet does show variation in species-level taxa in response to food items, there is greater commonality in response at the level of guilds. A goal for microbiome researchers should be to identify genes encoding microbial attributes that can define such guilds. This article is protected by copyright. All rights reserved
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Diet is one of the most common traits used to organize species of animals into niches. For ruminant herbivores, the breadth and uniqueness of their dietary niche are placed on a spectrum from browsers that consume woody (i.e., browse) and herbaceous (i.e., forbs) plants, to grazers with graminoid-rich diets. However, seasonal changes in plant availability and quality can lead to switching of their dietary niche, even within species. In this study, we examined whether a population of wood bison (Bison bison athabascae) in northeast Alberta, Canada, seasonally switched their foraging behavior , and if so, whether this was associated with changes in nutrient acquisition. We hypothesized that bison should switch foraging behaviors from grazing in the winter when standing, dead graminoids are the only foliar plants readily available to browsing during spring and summer as nutritious and digestible foliar parts of browse and forbs become available. If bison are switching foraging strategy to maximize protein consumption, then there should be a corresponding shift in the nutritional niche. Alternatively, if bison are eating different plants, but consuming similar amounts of nutrients, then bison are switching their dietary niche to maintain a particular nutrient composition. We found wood bison were grazers in the winter and spring, but switch to a browsing during summer. However, only winter nutrient consumption of consumed plants differed significantly among seasons. Between spring and summer, bison maintained a specific nutritional composition in their diet despite compositional differences in the consumed plants. Our evidence suggests that bison are selecting plants to maintain a target macronutrient composition. We posit that herbivore's can and will switch their dietary niche to maintain a target nutrient composition.
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Anthropogenic environments can offer rich sources of energy to urban wildlife, but little is known about how they impact on nutritional balance and food selection. Common mynas (Sturnus tristis) provide a powerful model system for testing the nutritional constraints and priorities of an invasive species that has successfully adapted to urban environments. Here, we use behavioral observations, field-based feeding trials, videography, and the right-angled mixture triangle model (RMT) to examine the macronutrient preferences of these invasive birds. Our behavioral observations showed that mynas consumed insects (40.6%), worms (33.2%), human discards (17.6%), and plants (8.6%). Our feeding trials using nutritionally defined foods showed that mynas had a clear preference for food dishes containing only high-protein (HP) pellets over high-lipid (HL) or high-carbohydrate (HC) pellets. In addition, mixed feeders were also presented in 2 combinations: 1) contained equal proportions of HP and HC pellets and 2) equal proportions of HP and HL pellets. HP pellets were selectively consumed from both mixed feeders, this involving an increase in feeding time. Overall, the RMT showed that mynas consumed a higher proportion of protein from the feeders than in their natural diet. Furthermore, the majority of our observations of birds feeding at the dishes containing HP foods ended in intraspecific aggression, suggesting that protein is a contestable resource. These results suggest that mynas at our urban study site are deficient in protein relative to fats and carbohydrates.
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Anthropogenic environments can offer rich sources of energy to urban wildlife, but little is known about how they impact on nutritional balance and food selection. Common mynas (Sturnus tristis) provide a powerful model system for testing the nutritional constraints and priorities of an invasive species that has successfully adapted to urban environments. Here, we use behavioral observations, field-based feeding trials, videography, and the right-angled mixture triangle model (RMT) to examine the macronutrient preferences of these invasive birds. Our behavioral observations showed that mynas consumed insects (40.6%), worms (33.2%), human discards (17.6%), and plants (8.6%). Our feeding trials using nutritionally defined foods showed that mynas had a clear preference for food dishes containing only high-protein (HP) pellets over high-lipid (HL) or high-carbohydrate (HC) pellets. In addition, mixed feeders were also presented in 2 combinations: 1) contained equal proportions of HP and HC pellets and 2) equal proportions of HP and HL pellets. HP pellets were selectively consumed from both mixed feeders, this involving an increase in feeding time. Overall, the RMT showed that mynas consumed a higher proportion of protein from the feeders than in their natural diet. Furthermore, the majority of our observations of birds feeding at the dishes containing HP foods ended in intraspecific aggression, suggesting that protein is a contestable resource. These results suggest that mynas at our urban study site are deficient in protein relative to fats and carbohydrates.
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In this chapter, we first trace the history of the concept of ecological niche and see how its meanings varied with the search for a theory of ecology. The niche concept has its roots in the Darwinian view of ecosystems that are structured by struggle for survival and, originally, the niche was perceived as an invariant place within the ecosystem, that would preexist the assembly of the ecosystem. The concept then slipped towards a sense in which the niche, no longer a pre-existing ecosystem structure, eventually became a variable that would in turn have to be explained by the competitive exclusion principle and the coevolution of species. The niche concept used at that time, while more operational from an empirical point of view than the previous one, suffered however from an ill-founded definition. A recent refoundation by Chase & Leibold enabled to overcome some of the definitional difficulties. We then present how, in contemporary ecology, the niche concept is recruited to explain biodiversity and species coexistence patterns. We show how, in parallel, neutralist models, by succeedingly explaining some ecological patterns without resorting to explanations in terms of niche, have questioned the explanatory virtues of the niche concept. In conclusion, it seems that the forunes and misfortunes of the niche concept can be seen as a reflection of the difficulties of ecology to give birth to a theory that would be both predictive and explanatory.
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Specialization is a concept based on a broad theoretical framework developed by evolutionary biologists and ecologists. In the past 10 years, numerous studies have reported that - in many contexts - generalist species are "replacing" specialist species. We review recent research on the concept of the ecological niche and species specialization, and conclude that (1) the observed worldwide decline in specialist species is predicted by niche theory, (2) specialist declines cause "functional homogenization" of biodiversity, and (3) such homogenization may be used to measure the impact of disturbance on communities. Homogenization at the community level could alter ecosystem functioning and productivity, as well as result in the deterioration of ecosystem goods and services. We propose community-level specialization as an indicator of the impact of global changes (habitat and climate disturbances) on biodiversity.
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Many crustaceans have been moved to new locations where they have caused ecological or economic problems, that is, have become invasive. This article focuses on the role of animal behavior in contributing to their success. Certain behaviors are particularly relevant, including (1) feeding: outcompeting native species for food or eating native species of concern; (2) predator avoidance: the invader may be more successful at avoiding predators than native species; (3) habitat: invasive species may displace natives from their habitat or may alter the environment; (4) aggressive behavior: may contribute to (1) or (3) above; (5) movements: if the invader undergoes extensive migrations, it can spread more rapidly; (6) plasticity: (learning) if the invader is “smarter” than native species, it may be more likely to outcompete them for habitat and/or food; and (7) reproduction (though not strictly reproductive behavior per se). These behaviors are discussed with respect to invasive crustaceans, including freshwater and marine examples.
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The butterfly is a specialist of oligotrophic ecosystems. Population viability analysis predicted the species to be stable in Belgium and to collapse in the Netherlands with reduced host plant quality expected to drive species decline in the latter. We tested this hypothesis by rearing caterpillars from Belgian and Dutch sites on host plants (the cranberry, ). Dutch plant quality was lower than Belgian one conferring lower caterpillar growth rate and survival. Reintroduction and/or supplementation may be necessary to ensure the viability of the species in the Netherlands, but some traits may have been selected solely in Dutch caterpillars to cope with gradual changes in host plant quality. To test this hypothesis, the performance of Belgian and Dutch caterpillars fed with plants from both countries were compared. Dutch caterpillars performed well on both plant qualities, whereas Belgian caterpillars could not switch to lower quality plants. This can be considered as an environmentally induced plastic response of caterpillars and/or a local adaptation to plant quality, which precludes the use of Belgian individuals as a unique solution for strengthening Dutch populations. More generally, these results stress that the relevance of local adaptation in selecting source populations for relocation may be as important as restoring habitat quality.
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The mountain gorilla (Gorilla beringei beringei) lives in two geographically separated populations, Bwindi Impenetrable National Park, Uganda and in three national parks spanning the Virunga mountain region in Rwanda, Democratic Republic of Congo, and Uganda. The altitude, climate and plant composition of these habitats differ. Our goal was to compare the diets of gorillas living in each of these habitats. The nutrients in staple foods and in the diets of individuals in a group of gorillas in Bwindi (N = 12 individuals) and a group in the Virungas (N = 7 individuals) were compared to determine if differences in dietary composition affected concentrations of nutrients in their diets. At both sites gorilla diets consisted primarily of herbaceous leaves, but the diet of Bwindi gorillas contained more tree leaves, fruit, pith and dry wood, and fewer stems. Despite differences in habitat and dietary composition, the nutrient concentrations in both gorilla diets were remarkably similar. On a dry matter basis, the diets and staple foods of Bwindi and Virunga gorillas contained similar concentrations of crude protein (CP), fibre (NDF) and non-structural carbohydrates (TNC). Bwindi gorillas ate diets containing 18% CP, 43% NDF and 19% TNC on a dry-matter basis, while the diets of the Virunga gorillas contained 17% CP, 41% NDF and 18% TNC. Our results demonstrate that gorillas consume diets that differ by plant species and part, but contain similar concentrations of nutrients. This suggests that classifying animals by broad dietary strategy (e.g. frugivory and folivory) does not provide a reliable indicator of the nutritional quality of their diet, and that our previous assumptions about these categories should be re-evaluated.
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Personality differences are a widespread phenomenon throughout the animal kingdom. Past research has focused on the characterization of such differences and a quest for their proximate and ultimate causation. However, the consequences of these differences for ecology and evolution received much less attention. Here, we strive to fill this gap by providing a comprehensive inventory of the potential implications of personality differences, ranging from population growth and persistence to species interactions and community dynamics, and covering issues such as social evolution, the speed of evolution, evolvability, and speciation. The emerging picture strongly suggests that personality differences matter for ecological and evolutionary processes (and their interaction) and, thus, should be considered a key dimension of ecologically and evolutionarily relevant intraspecific variation.
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Summary1. Ecological specialization is one of the main concepts in ecology and conservation. However, this concept has become highly context-dependent and is now obscured by the great variability of existing definitions and methods used to characterize ecological specialization.2. In this study, we clarify this concept by reviewing the strengths and limitations of different approaches commonly used to define and measure ecological specialization. We first show that ecological specialization can either be considered as reflecting species’ requirements or species’ impacts. We then explain how specialization depends on species-specific characteristics and on local and contingent environmental constraints. We further show why and how ecological specialization should be scaled across spatial and temporal scales, and from individuals to communities.3. We then illustrate how this review can be used as a practical toolbox to classify widely used metrics of ecological specialization in applied ecology, depending on the question being addressed, the method used, and the data available.4. Synthesis and applications. Clarifying ecological specialization is useful to make explicit connections between several fields of ecology using the niche concept. Defining this concept and its practical metrics is also a crucial step to better formulate predictions of scientific interest in ecology and conservation. Finally, understanding the different facets of ecological specialization should facilitate to investigate the causes and consequences of biotic homogenization and to derive relevant indicators of biodiversity responses to land-use changes.