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87 results for “trophic niche”
The bite force-gape relationship as an avenue of biomechanical adaptation to trophic niche in two salmonid fishes
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Predicting the competitive interactions and trophic niche consequences of a globally invasive fish with threatened native species
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Data from: Mechanisms of trophic niche compression: evidence from landscape disturbance
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Floods connect tropical river-floodplain food webs but shrink fish community isotopic trophic niches
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The dynamic trophic niche of an island bird of prey
Optimal Foraging Theory predicts an inverse relationship between the availability of preferred prey and niche width in animals. Moreover, when individuals within a population have identical prey preferences and preferred prey is scarce, a nested pattern of trophic niche is expected if opportunistic and selective individuals can be identified. Here, we examined intraspecific variation in the trophic niche of a resident population of striated caracara (Phalcoboenus australis) on Isla de los Estados (Staten Island), Argentina, using pellet and stable isotope analyses. While this raptor specializes on seabird prey, we assessed this population's potential to forage on terrestrial prey, especially invasive herbivores as carrion, when seabirds are less accessible. We found that the isotopic niche of this species varies with season, age, breeding status and, to a lesser extent, year. Our results were in general consistent with classic predictions of the Optimal Foraging Theory, but we also explore other possible explanations for the observed pattern. Isotopic niche was broader for groups identified a priori as opportunistic (i.e., non-breeding adults during the breeding season and the whole population during the non-breeding season) than it was for individuals identified a priori as selective. Results suggested that terrestrial input was relatively low, and invasive mammals accounted for no more than 5% of the input. The seasonal pulse of rockhopper penguins likely interacts with caracara's reproductive status by constraining the spatial scale on which individuals forage. Niche expansion in spatially flexible individuals did not reflect an increase in terrestrial prey input, rather it may be driven by a greater variation in the types of marine prey items consumed.
Data from: Patterns of trophic niche divergence between invasive and native fishes in wild communities are predictable from mesocosm studies
1. Ecological theory attempts to predict how impacts for native species arise from biological invasions. A fundamental question centres on the feeding interactions of invasive and native species: whether invasion will result in increased interspecific competition, which would result in negative consequences for the competing species, or trophic niche divergence, which would facilitate the invader's integration into the community and their coexistence with native species. 2. Here, the feeding interactions of a highly invasive fish, topmouth gudgeon Pseudorasbora parva, with three native and functionally similar fishes were studied to determine whether patterns of either niche overlap or divergence detected in mesocosm experiments were apparent between the species at larger spatial scales. Using stable isotope analysis, their feeding relationships were assessed initially in the mesocosms (1000 L) and then in small ponds (<400 m2) and large ponds (>600 m2). 3. In the mesocosms, a consistent pattern of trophic niche divergence was evident between the sympatric fishes, with niches shifting further apart in isotopic space than suggested in allopatry, revealing that sharing of food resources was limited. Sympatric P. parva also had a smaller niche than their allopatric populations. 4. In eight small ponds where P. parva had coexisted for several years with at least one of the fish species used in the mesocosms, strong patterns of niche differentiation were also apparent, with P. parva always at a lower trophic position than the other fishes, as also occurred in the mesocosms. Where these fishes were sympatric within more complex fish communities in the large ponds, similar patterns were also apparent, with strong evidence of trophic niche differentiation. 5. Aspects of the ecological impacts of P. parva invasion for native communities in larger ponds were consistent with those in the mesocosm experiments. Their invasion resulted in divergence in trophic niches, partly due to their reduced niche widths when in sympatry with other species, facilitating their coexistence in invaded ecosystems. Our study highlights the utility of controlled mesocosm studies for predicting the trophic relationships that can develop from introductions of non-native species into more complex ecosystems and at larger spatial scales.
Data from: Trophic niche changes associated to habitat fragmentation in a Neotropical bat species
Habitat fragmentation could alter ecological traits including species trophic habits. Here, we used carbon and nitrogen stable isotope ratios to establish differences in isotopic niche width and food resource use between forest fragments and the continuous forest for the phyllostomid frugivorous bat Artibeus lituratus. Using mist nests, we captured bats from two forest fragments and two sites in continuous forest, and sampled from each individual captured three body tissues with contrasting turnover rates (skin, muscle and liver). Samples were collected between February-March (austral summer) and between August-September (austral winter). In addition, in each sampling site and season we collected potential food resources (fruits and insects) consumed by our A. lituratus. Our findings indicate that A. lituratus had a predominantly omnivorous diet, with high consumption of insects during summer in forest fragments. The increasing consumption of insects in these fragments seems to have led to a wider isotopic niche, in relation to the continuous forest. Because A. lituratus is typically a seed disperser, changes in trophic habits in the forest fragments from frugivory to insectivory may diminish their role in forest regeneration.
Data from: Novel trophic niches drive variable progress toward ecological speciation within an adaptive radiation of pupfishes
Adaptive radiation is recognized by a rapid burst of phenotypic, ecological, and species diversification. However, it is unknown whether different species within an adaptive radiation evolve reproductive isolation at different rates. We compared patterns of genetic differentiation among nascent species within an adaptive radiation of Cyprinodon pupfishes using genotyping by sequencing. Similar to classic adaptive radiations, this clade exhibits rapid morphological diversification rates and two species are novel trophic specialists, a scale-eater and hard-shelled prey specialist (durophage), yet the radiation is less than 10,000 years old. Both specialists and an abundant generalist species all coexist in the benthic zone of lakes on San Salvador Island, Bahamas. Based on 13,912 single-nucleotide polymorphisms (SNPs), we found consistent differences in genetic differentiation between each specialist species and the generalist across seven lakes. The scale-eater showed the greatest genetic differentiation and clustered by species across lakes, whereas durophage populations often clustered with sympatric generalist populations, consistent with parallel speciation across lakes. However, we found strong evidence of admixture between durophage populations in different lakes, supporting a single origin of this species and genome-wide introgression with sympatric generalist populations. We conclude that the scale-eater is further along the speciation-with-gene-flow continuum than the durophage and suggest that different adaptive landscapes underlying these two niche environments drive variable progress toward speciation within the same habitat. Our previous measurements of fitness surfaces in these lakes support this conclusion: the scale-eating fitness peak may be more distant than the durophage peak on the complex adaptive landscape driving adaptive radiation.
Data from: Realized trophic niche driven by apparent competition: an example with marsupials
According to apparent competition theory, the co-occurrence of two species that share the same predators appears to affect each other's population growth and abundance. However, due to habitat loss and over-hunting, top predators are being made rare worldwide. Considering that apparent competitors share similar resources, we would expect the absence of top predators to reflect in changes on prey realized trophic niches. To test our hypothesis, we developed a model to predict the abundance ratio of apparent competitor species based on changes in their realized trophic niches. We tested our model against field data on the Neotropical marsupials Didelphis aurita and Metachirus nudicaudatus. Our results revealed that D. aurita and M. nudicaudatus are two species under apparent competition and their realized trophic niche and diet overlap change according to the presence of top predators. The model was able to predict the actual relative abundances of D. aurita and M. nudicaudatus in the three empirical studies analyzed. Our study presents quantitative support to the apparent competition theory; however, the model's applications to other groups still need to be verified. Additionally, our study shows that the lack of top predators has consequences on the realized trophic niche of their prey, and therefore, we reinforce that conservation plans need to focus on the effects of top predator loss on ecosystems.
Data from: Trophic niche size and overlap decreases with increasing ecosystem productivity
The production and transfer of biomass through trophic relationships is a core ecosystem function. The movement of energy through the food web is mediated by organisms operating in their niche space. For generalists, the size of this niche space is inherently plastic and changes in response to available food sources. Therefore, this relationship between ecosystem productivity and niche size is an important determinant of ecosystem function. Competing theories about the nature of this relationship predict that as productivity increases niche size will either increase as species capitalize on a general increase in resource availability or decrease as it becomes viable to focus on preferred production channels. Here, we test these two competing theoretical frameworks using a novel approach to determine trophic niche size using stable isotope analysis and hypervolume metrics. Resource use is quantified in two generalist fish species at three productivity levels in a seagrass ecosystem. Niche size of both species was inversely related to seagrass productivity, consistent with the hypothesis that increasing productivity allows species to focus on a narrower diet. This pattern describes the relationship between ecosystem production and niche size and provides an empirical ecological explanation for the resource maximization behaviors commonly observed in nature.
FIGURE 1 in The trophic niche of sculpins Cottus spp. in forage fish assemblages of boreal lakes
FIGURE 1 Biplots of trophic niche positions (total mass size-adjusted muscle δ15N vs δ13C) for individual small-bodied fishes sampled from representative Far North Lakes, (a) Goods and (b) Kapkichi and Near North Lakes, (c) Temagami and (d) Wanapitei, of Ontario, Canada. Trophic niches, represented by fitted 1 SD bivariate ellipses, of Cottus spp (,) and all other species (,); numbers beside ellipses correspond to the species index of Table 2
FIGURE 2 in The trophic niche of sculpins Cottus spp. in forage fish assemblages of boreal lakes
FIGURE 2 Boxplots (, median;, interquartile range;, 1.5 times the length of the box;, outliers) showing separation of trophic niche positions in δ13C–δ15N space (distance between centroids) between Cottus spp. and (a) all co-habiting small-bodied fish species and (b) Perca flavescens, for Far North and Near North Lakes of Ontario, Canada. Test results are for two-sample t-tests
Data from: Trophic niches of Collembola communities change with elevation but also with body size and life form
<p>Climate change increases habitat loss of endemic tree species and drives forest conversion in mountainous forests. Elevational gradients provide the opportunity to predict possible consequences of such changes. While species compositions of various taxa have been investigated along elevational gradients, data on trophic changes in soil-dwelling organisms is scarce. Here, we analyze trophic changes of the Collembola community along the northern slope of Changbai Mountain, China. We sampled seven elevations (800-1700 m asl) with 150 m elevational difference along a primary forest gradient. At eight subplots per elevation, we categorized Collembola species into life forms, measured individual body lengths and bulk stable isotopes. Mean and minimum <span>Δ<sup>15</sup>N and mean Δ<sup>13</sup>C increased with increasing elevation, while the range of Δ<sup>15</sup>N decreased. Maximum and minimum of Δ<sup>13</sup>C differed between elevations but showed no linear response. Isotopic uniqueness increased with elevation. Δ<sup>15</sup>N values of Collembola species occurring across all elevations increased with elevation. Changes in Δ<sup>15</sup>N with elevation were most pronounced in hemiedaphic species. Δ<sup>15</sup>N </span>values <span>increased with decreasing body size in hemiedaphic and euedaphic species. </span>Δ<sup>13</sup>C increased strongest with elevation in euedaphic species. <span>Overall, the</span> results suggest that<span> Collembola species functioning as primary decomposers shift towards functioning as secondary decomposers at higher elevations. Further</span>, access to alternative food resources may depend on Collembola life form and body size, this relationship, however, likely varies between ecosystems. Collembola functioning as secondary decomposers in coniferous forests may function as primary decomposers under climate driven forest conversion as species boundaries of tree species of lower elevations expand.</p>
Trophic niche partitioning of seven skate species (Rajidae), in the Northern and Central Patagonia, Argentina-Raw data
<p>Skate´s content stomach information and statistics information</p>
Data from: Trophic niche width increases with bill size variation in a generalist passerine: a test of the niche variation hypothesis
1. The niche variation hypothesis (NVH) predicts that populations with wider niches are phenotypically more variable than populations with narrower niches, which is frequently used to explain diversifying processes such as ecological release. However, not all empirical evidence supports the NVH. Furthermore, a relationship between population phenotypic variation and niche width can be caused by sexual selection or environmental gradients, which should be carefully considered along with competition in explaining niche variation. 2. In this study we used eight populations of a generalist passerine species, Paradoxornis webbianus (vinous-throated parrotbill), to test the NVH. We assessed evidence of ecological sexual dimorphism and environmental gradients in bill morphology of P. webbianus. A total of 170 P. webbianus from eight sites ranging 24-2,668 m in altitude were included in this study. We used two principal components to quantify bill morphology, one describes bill size and the other describe bill slenderness. We used stable carbon and nitrogen isotope values of bird feathers to quantify trophic positions, and we estimated population trophic niche width using Bayesian standardized ellipse area. 3. Paradoxornis webbianus with larger and more slender bills fed at higher trophic levels and population trophic niche width tended to increase with bill size variation, supporting the NVH. The males had larger bills and marginally higher nitrogen isotope values than the females, suggesting ecological sexual dimorphism. Despite a positive correlation between bill size and wing length indicating sexual selection for larger male size, only three of the eight populations showed both male-biased bill size and male-biased wing length. Sexual dimorphism explained 13%-64% of bill size variation across sites, suggesting its role in niche variation could vary greatly among populations. The variation in bill slenderness in P. webbianus increased with elevation. However, neither bill size variation nor trophic niche width changed with elevation. Therefore, environmental gradients that could be reflected in the elevation are not likely to drive the observed morphological and niche variation. 4. This study provides an empirical case for the NVH and highlights the importance to investigate sexual dimorphism and environmental gradients in the studies of niche dynamics.
Data for the article: Trophic niche partitioning between two prey and their incidental predators revealed various threats for an endangered species
<p><span>Documenting trophic niche partitioning and resource use within a community is critical to evaluate underlying mechanisms of coexistence, competition or predation. Detailed knowledge about foraging is essential as it may influence the vital rates, which, in turn, can affect trophic relationships between species and population dynamics. The aims of this study were to evaluate resource and trophic niche partitioning in summer/autumn between the endangered Atlantic-Gaspésie caribou (<em>Rangifer tarandus caribou</em>) population, moose (<em>Alces americanus</em>) and their incidental predators, the black bear (<em>Ursus americanus</em>) and coyote (<em>Canis latrans</em>), and to quantify the extent to which these predators consumed caribou. Bayesian isotopic analysis showed a small overlap in trophic niche for the two sympatric ungulates suggesting a low potential for resource competition. Our result also revealed that caribou occupied a larger isotopic niche area than moose, suggesting a greater diversity of resources used by caribou. Not surprisingly, coyote consumed mainly deer (<em>Odocoileus virginianus</em>), moose, snowshoe hare (<em>Lepus americanus</em>), and occasionally caribou, while bears consumed mainly vegetation and, to a lesser extent, moose and caribou. As coyotes and bears also feed on plant species, we documented trophic niche overlap between caribou and their predators, as searching for similar resources can force them to use the same habitats and thus increase the encounter rate and, ultimately, mortality risk for caribou. Although the decline of the Gaspésie caribou population is mostly driven by habitat-mediated predation, we found evidence that the low level of resource competition with moose added to the shared resources with incidental predators, mainly bears, may contribute to jeopardize the recovery of this endangered caribou population. Highlighting the trophic interaction between species is needed to establish efficient conservation and management strategies to insure the persistence of endangered populations. The comparison of trophic niches of species sharing the same habitat or resources is fundamental to evaluate the mechanisms of coexistence or competition and eventually predict the consequences of ecosystem changes in the community.</span></p>
To share or not to share: DNA metabarcoding reveals trophic niche overlap between sympatric trawling bats.
<p>All genetic sequences used in the scientific paper entiteled "To share or not to share: DNA metabarcoding reveals trophic niche overlap between sympatric trawling bats".</p>
Data from: Seasonal change in trophic niche of adfluvial arctic grayling (Thymallus arcticus) and coexisting fishes in a high-elevation lake system
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Data from: Trophic niche ontogeny and palaeoecology of early Toarcian Stenopterygius (Reptilia: Ichthyosauria)
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Data from: Patterns of trophic niche divergence between invasive and native fishes in wild communities are predictable from mesocosm studies
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