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The structure of mesopredators’ communities is complex and results from a multidimensional web of interactions such as top-down and bottom-up regulation or intraguild interactions. However, these interactions may change geographically along species’ distribution ranges. The pine marten (Martes martes) and stone marten (Martes foina) are 2 similar-sized mustelids with overlapping ecological traits and a wide distribution overlap. The absence of stone martens from potentially adequate areas has been advocated as resulting from competitive exclusion by pine martens. Particularly, the preference of both species for mammalian rodents could be the main driver of such competitive stress. However, their elusive behavior and morphological similarity of their scats often precluded the evaluation of their ecological traits in areas of co-occurrence. Using camera trapping and diet analysis on genetically identified scats, we evaluated the interactions between pine and stone martens in the southwestern limit of their range along 3 ecological niche dimensions: spatial, trophic, and temporal, under a hypothesis of competitive dominance of pine martens. We found no spatial segregation, and that coexistence was facilitated by seasonally adjusted shifts along the trophic and temporal axes. While both species often co-occurred, during the season of low food resources, pine martens exploited the less profitable feeding resource. Moreover, they not only displayed an activity pattern that limited their access to rodents, but also reduced the probabilities of direct encounters with stone martens. We suggest that the dominance position has changed in favor of the stone marten in our study area, probably as a result of habitat quality and range edge effects. These findings support the relative instability of interspecific interactions among similar-sized species, which should be evaluated using multidimensional and site-specific approaches.

Understanding the processes that enable species coexistence has important implications for assessing how ecological systems will respond to global change. Morphology and functional similarity increase the potential for competition, and therefore, co‐occurring morphologically similar but genetically unique species are a good model system for testing coexistence mechanisms. We used DNA metabarcoding and high‐throughput sequencing to characterize for the first time the trophic ecology of two recently described cryptic bat species with parapatric ranges, Myotis escalerai and Myotis crypticus. We collected fecal samples from allopatric and sympatric regions and from syntopic and allotopic locations within the sympatric region to describe the diets both taxonomically and functionally and compare prey consumption with prey availability. The two bat species had highly similar diets characterized by high arthropod diversity, particularly Lepidoptera, Diptera and Araneae, and a high proportion of prey that is not volant at night, which points to extensive use of gleaning. Diet overlap at the prey item level was lower in syntopic populations, supporting trophic shift under fine‐scale co‐occurrence. Furthermore, the diet of M. escalerai had a marginally lower proportion of not nocturnally volant prey in syntopic populations, suggesting that the shift in diet may be driven by a change in foraging mode. Our findings suggest that fine‐scale coexistence mechanisms can have implications for maintaining broad‐scale diversity patterns. This study highlights the importance of including both allopatric and sympatric populations and choosing meaningful spatial scales for detecting ecological patterns. We conclude that a combination of high taxonomic resolution with a functional approach helps identify patterns of niche shift. We used DNA metabarcoding, high‐throughput sequencing, and a functional approach to test the role of trophic partitioning in enabling species coexistence across spatial scales through characterizing the trophic ecology of two cryptic bat species, Myotis escalerai and Myotis crypticus, in sympatric versus allopatric locations. Although the two species had similar diets characterized by high arthropod diversity, diet overlap at the prey‐item level was lower in locally sympatric than allopatric locations; and the functional analysis suggested that this trophic shift may be driven by a change in foraging mode from gleaning to aerial hawking. Our findings show that fine‐scale coexistence mechanisms can contribute to maintaining broad‐scale diversity patterns.

The study compares the isotopic niche (δ13C–δ15N) of three species of penaeid shrimps (Xiphopenaeus kroyeri, Artemesia longinaris and Litopenaeus schmitti) that are targets of fishing in south-eastern Brazil. The two hypotheses raised are based on the niche theory, in which the coexistence between organisms that have similar dietary demands is possible due to trophic partitioning: (i) shrimp species that share the habitat have segregated isotopic niches; and (ii) stages of maturity and genders vary with the trophic habitat (δ13C) and/or trophic position (δ15N). In multispecific fishing grounds, the isotopic niches of the shrimp species were segregated or had low overlap, indicating trophic partitioning. The intraspecific comparison of δ13C and δ15N showed a similar trend in all species. For δ13C, the values were more enriched in adult individuals than in juveniles, but similar between males and females. For δ15N, adult individuals also had more enriched values, and males were more enriched than females. The results confirm the hypotheses raised, and the assumptions of niche theory apply to these penaeid shrimps.

Stable isotope analyses have refined the study of trophic niche diversity within an ecosystem, yet traditional trophic partitioning methods may not be appropriate to identify variation among groups with similar dietary requirements. By building on vector‐based analyses, we introduce a baseline‐standardized isotopic vector analysis (BaSIVA) to visualize dietary variation while accounting for isotopic discrepancies between locations. To test the effectiveness of our new method, we collected muscle samples from eleven species of Loricarioidea in five assemblages in Northern Peru. Loricarioidea is a large, ecomorphologically diverse superfamily of scraping‐feeding fishes. Most feed on an indistinguishable mix of detritus and algae, but some lineages have specialized diets of wood, seeds, and macroinvertebrates, making them an excellent group to study trophic variation. Isotopic data were collected using mass spectrometric isotope analyses, and communities were standardized by calculating a mean baseline (algae and periphyton) for each location. The entire community was shifted by subtracting the baseline of 15N and 13C from the consumers at each location, which allowed for comparison between assemblages. Incremental differences of 15N and 13C from the baseline were found via vector analysis, and the azimuth and module of each consumer were calculated. Standardization resulted in a significant shift of assemblages within the isotopic biplot, and vector analysis shows three trophic groups primarily described by differences in carbon assimilation. Isotopic variation between species may account for some diversification in jaw shape within the Loricarioidea, but BaSIVA suggests several instances of trophic overlap in different jaw morphologies. Moreover, results from BaSIVA are better able to delineate trophic groups than traditional trophic positioning methods while accounting for variation in basal resources. We suggest a baseline‐standardized vector analysis should be the standard for vector‐based stable isotope analysis in riverine environments with similar baseline resources.

The polyploid lineage of the cyprinid genus Labeobarbus provides an excellent model for studying trophic-driven adaptive radiations. Four recently discovered diversifications in rivers of the Ethiopian Highlands (East Africa) show independent repeated evolutions of mouth polymorphisms each represented by four mouth phenotypes: (1) generalized, (2) thick-lipped, (3) scraping, and (4) large-mouthed. Using stable isotope and gut content analyses, we tested hypothesis on the partitioning of trophic resources within each radiation and revealed differences in degree of diversification between radiations. Three out of four radiations showed partitioning of trophic resources within five trophic niches: (1) detritophagy, (2) macrophytophagy, (3) benthophagy, (4) periphyton feeding, and (5) piscivory. The radiations are likely to be at different stages of diversification. One radiation with a similar set of mouth phenotypes was not trophically divergent and showed a remarkable decoupling of form and function. A case of ecologically non-functional mouth polymorphism is a bright example of the Liem’s paradox and supports a concept of the plasticity-first evolution. This might be based on pre-existing genomic templates inherited from ancestral lineages that participated in the polyploidization of the Labeobarbus lineage. Predetermined and preadaptive mouth polymorphism can be considered a key innovation of Labeobarbus that promotes to resource-based diversification.

Increasing interest in the marine trophic dynamics of Pacific salmon has been motivated by the recognition of their sensitivity to changing climate and to the competitive effects of hatchery fish on wild stocks. It has become more common to use stable isotopes to supplement traditional diet studies of salmon in the ocean; however, there have been no integrated syntheses of these data to determine whether stable isotope analyses support the existing conventional wisdom of feeding strategies of the Pacific salmon. We performed a meta-analysis of stable isotope data to examine the extent of trophic partitioning among five species of Pacific salmon during their marine lives. Pink, sockeye, and chum salmon showed very high overlap in resource use and there was no consistent evidence for chum relying on alternative food webs dominated by gelatinous zooplankton. δ¹⁵N showed that Chinook and coho salmon fed at trophic levels higher than the other three species. In addition, these two species were distinctly enriched in ¹³C, suggesting more extensive use of coastal food webs compared to the more depleted (pelagic) signatures of pink, sockeye, and chum salmon. This paper presents the first synthesis of stable isotope work on Pacific salmon and provides δ¹⁵N and δ¹³C values applicable to research on the fate of the marine derived nutrients these organisms transport to freshwater and riparian ecosystems.

We investigated trophic resource partitioning in seven syntopic anurans from low- and mid-elevation stream habitats of a tropical riparian ecosystem by utilising stomach content analysis (SCA) and stable isotope analysis (SIA). Our SCA data revealed dietary similarities, narrow trophic niche breadth, and low dietary niche overlap in Ansonia muelleri, Limnonectes magnus, Occidozyga laevis, Megophrys stejnegeri, Pulchrana grandocula, Sanguirana mearnsi , and Staurois natator which could be attributed to these anurans’ selection of available local prey items. We confirmed ant-specialisation (myrmecophagy) of the Mindanao island endemic bufonid A. muelleri based on our temporal SCA dietary data. Our SIA estimates of assimilation of potential prey sources confirmed that L. magnus , P. grandocula , and O. laevis are generalist predators, opportunistically feeding on locally abundant insect prey items. This study on trophic resource partitioning in syntopic anurans provides the first picture of trophic interactions, i.e., predation and competition in stream communities in tropical riparian zones of a watershed ecosystem in northeast Mindanao of the southern Philippines.

Across the northern hemisphere, ungulates are expanding in range and abundance, forming novel communities in increasingly human‐modified landscapes. These shifts drive new interactions over available food resources, but patterns of resource use and partitioning in Europe's multi‐species systems remain poorly understood. This study examined seasonal diets and resource partitioning in diverse cervid communities (moose, roe deer, red deer, and fallow deer) across two Swedish landscapes (coastal‐boreal and boreo‐nemoral) differing in deer density and land use. Based on their foraging strategies, we expected (Hypothesis 1) diet richness and dietary niche width to be greater in intermediate feeders (red and fallow deer) than in browsers (moose and roe deer), (Hypothesis 2) trophic partitioning between browsers and intermediate feeders to be driven mainly by graminoid use, and (Hypothesis 3) intra‐ and interspecific overlap to vary with season, deer density, habitat diversity, and proportion of arable land. DNA metabarcoding of 2568 fecal samples showed that deer consumed plants from over 70 families, though diets were typically dominated by fewer than 10. Vaccinium shrubs were key forages year‐round, while birch and willow dominated during the growing season. Moose consumed large amounts of pine in spring and winter (> 50% in the boreo‐nemoral, 35%–40% in the coastal‐boreal landscape), with less during summer‐autumn (~15%). Forbs were important for smaller deer, especially in spring and summer‐autumn, and more heavily used in winter in the boreo‐nemoral landscape, likely due to supplementary feeding with human‐provided food like hay or silage. Spruce use was low overall (< 5%), with fallow deer showing the highest intake. Consistent with Hypothesis 1, diet richness and niche width increased from moose to fallow deer. In partial support of Hypothesis 2, principal coordinates analysis (PCoA) revealed that graminoids contributed to trophic partitioning, but the pattern was not a strict browser–intermediate feeder divide. Moose consistently separated from the smaller deer due to avoidance of graminoids and reliance on pine and juniper, while roe deer, although a browser, sometimes overlapped with red and fallow deer through greater use of graminoids. During winter in the coastal‐boreal landscape, wavy hairgrass (Avenella flexuosa) contributed to the significant separation between browsing roe deer and intermediate‐feeding red deer diets, consistent with Hypothesis 2. Diet overlap among smaller deer varied with season and landscape. Intraspecific overlap was the highest in moose and the lowest in fallow deer, declining during summer–autumn across species. Overlap was influenced by deer density, habitat diversity, and arable land, consistent with Hypothesis 3, but effects were species‐specific and explained only limited variation. Our results highlight the dietary plasticity of red and fallow deer, which may intensify resource competition with moose and roe deer in multi‐species systems, particularly where supplementary feeding is common. These insights support adaptive, multi‐species management of deer in northern ecosystems. We used DNA metabarcoding of 2,568 fecal samples to examine seasonal diets and resource partitioning among four deer species (moose, roe deer, red deer, fallow deer) across two Swedish landscapes. Deer consumed a wide range of plants, but diets were typically dominated by a few key taxa, with distinct dietary separation between moose and smaller deer. Results reveal species‐specific plasticity and seasonal shifts in resource use, emphasizing the need for adaptive, multi‐species management in changing northern ecosystems.

Abstract Niche theory predicts that closely related and ecologically similar species with overlapping distribution ranges can coexist through resource partitioning that limits interspecific competition. However, studies examining the mechanisms promoting coexistence of top predators at a large geographical scale are still scant. Here, we describe the foraging ecology of 3 sympatric owl species (Northern long-eared owl [Asio otus], Tawny owl [Strix aluco], Eurasian eagle owl [Bubo bubo]) in the Mediterranean Basin. We review 160 studies reporting diet information (212,236 vertebrate preys) and investigate among-species differences in diet metrics (diversity, evenness, prey size, and proportion of mammals) and their variation along geographical and environmental gradients. Moreover, we test whether diet metrics differ in presence or absence of the other predators. All the 3 species mainly rely on small mammals, but they significantly differ in diet metrics. The smallest predator (i.e., long-eared owl) shows a higher level of specialism on small mammals (highest proportion but lowest diversity of mammals in the diet) compared to the larger ones. In addition, mean prey size significantly increases with predator body size (long-eared owl < tawny owl < eagle owl). Finally, interspecific competition results in an increase of diet diversity and evenness in the long-eared owl, and species’ diet also varies in response to environmental factors. The 3 species thus segregate along several dietary niche axes over a large spatial scale and according to both morphological characteristics (i.e., body size) and environmental variables. Such dietary niche segregation may adaptively buffer interspecific competition costs, ultimately allowing coexistence.

Mammals may experience physical changes from birth, and their diet varies at different stages of life. This study investigates the impact of development on the diet composition of three horseshoe bats: Rhinolophus euryale, R. hipposideros, and R. ferrumequinum in the Basque Country, north of the Iberian Peninsula. The diets of juvenile and adult individuals of each species were obtained by analysing their droppings using metabarcoding and then compared at (1) the taxonomic and (2) prey trait levels (size, flying speed, hardness). The diets of juvenile and adult individuals of R. euryale and R. hipposideros showed significant differences at the taxonomic level and regarding prey traits. In contrast, in the case of R. ferrumequinum, we could only observe discernible diet patterns through the trait analysis. Additionally, we discovered a shared pattern: younger individuals tend to feed on easier-to-hunt and/or handle smaller and smoother prey. The varying degrees of dissimilarity between juvenile and adult diets observed in this study suggest that the relative importance of psychomotor development, foraging strategies, prey discrimination, and/or spatial learning may differ among species. These findings contribute to conservation efforts, especially by recognising the dietary needs of juveniles for their survival and successful development.