Australian Tropical and Subtropical Rain Forest Community Assembly: Phylogeny,Functional Biogeography,and Environmental Gradients

To compare community assemblage patterns in tropical northeastern and subtropical central eastern Australia across selected gradients and scales, we tested the relationship of species traits with phylogenetic structure, and niche breadth. We considered phylogenetic relationships across current‐day species in assemblages in relation to rain forest species pool sizes, and trait values along gradients including elevation and latitude. Trait values were quantified across scales for seed size, leaf area, wood density and maximum height at maturity for 1137 species and 596 assemblages using trait gradient analysis (TGA). Local assemblages of subtropical species had narrower trait ranges, and higher niche breadth values than corresponding assemblages of tropical species. Leaf size and seed size increased at low latitudes, and community phylogenetic structure was most strongly correlated with seed traits in the subtropics, reflecting dispersal and re‐colonization processes. Elevation accounted for little of the variance in community phylogenetic structure or trait variation across local and regional scales. Stable moist forest areas retained many species from ancestral rain forest lineages across a range of temporally conserved habitats; species within assemblages were less related; and rain forest assemblages had higher functional diversity, but lower niche breadth. This suggests that on average, assemblages of species in stable areas had greater trait variation and narrower distributions. Historic and recent rain forest contraction and re‐expansion can result in recolonized areas that are dominated by species that are more related (phylogenetically) than by chance, have smaller, widely dispersed seeds, and greater niche breadth (broader distributions).     

Germination niche breadth varies inconsistently among three Asclepias congeners along a latitudinal gradient

• Species responses to climate change will be primarily driven by their environmental tolerance range, or niche breadth, with the expectation that broad niches will increase resilience. Niche breadth is expected to be larger in more heterogeneous environments and moderated by life history. Niche breadth also varies across life stages. Therefore, the life stage with the narrowest niche may serve as the best predictor of climatic vulnerability. To investigate the relationship between niche breadth, climate and life stage we identify germination niche breadth for dormant and non‐dormant seeds in multiple populations of three milkweed (Asclepias) species.
• Complementary trials evaluated germination under conditions simulating historic and predicted future climate by varying cold–moist stratification temperature, length and incubation temperature. Germination niche breadth was derived from germination evenness across treatments (Levins B_n), with stratified seeds considered less dormant than non‐stratified seeds.
• Germination response varies significantly among species, populations and treatments. Cold–moist stratification ≥4 weeks (1–3 °C) followed by incubation at 25/15 °C+ achieves peak germination for most populations. Germination niche breadth significantly expands following stratification and interacts significantly with latitude of origin. Interestingly, two species display a positive relationship between niche breadth and latitude, while the third presents a concave quadratic relationship.
• Germination niche breadth significantly varies by species, latitude and population, suggesting an interaction between source climate, life history and site‐specific factors. Results contribute to our understanding of inter‐ and intraspecific variation in germination, underscore the role of dormancy in germination niche breadth, and have implications for prioritising and conserving species under climate change.

     

Assessing the vulnerability of endemic diatom species in Lake Baikal to predicted future climate change: a multivariate approach

Diatoms in Lake Baikal exhibit significant spatial variation, related to prevailing climate, lake morphology and fluvial input into the lake. Here we have assessed the threats to endemic planktonic diatom species (through the development of empirical models), which form a major component of primary production within the lake. Multivariate techniques employed include redundancy analysis (RDA) and Huisman–Olff–Fresco (HOF) models. Our analyses suggest that eight environmental variables were significant in explaining diatom distribution across the lake, and in order of importance these are snow thickness on the ice, water depth, duration of days with white ice, suspended matter in the lake, days of total ice duration, temperature of the water surface in July, concentration of zooplankton and suspended organic matter. Impacts on dominant phytoplankton diatom species are highlighted using t‐value biplots. Predictions of future climate change on Lake Baikal are likely to result in shorter periods of ice cover, decreased snow cover across the lake in spring, increased fluvial input into the lake, and an increase in the intensification of surface water stratification during summer months. All these factors are likely to impact negatively on the slow‐growing, cold‐water endemics such as Aulacoseira baicalensis and Cyclotella minuta, which currently dominate diatom assemblages. Instead, taxa that are only intermittently abundant, at present, in offshore areas (e.g. Stephanodiscus meyerii) are likely to become more frequent. However, given the climatic gradient across the lake, the timing and extent of changes in community structure are likely to vary. Moreover, palaeolimnological records show that Lake Baikal diatom assemblages have been dynamic throughout the Holocene, with both endemic and cosmopolitan species exhibiting periods of dominance. Effects of climate change on the entire lake ecosystem may yet be profound as the structure of the pelagic food web may change from one based on endemic diatom taxa to one dominated by nondiatom picoplankton, and as limnological functioning (e.g. stratification and mixing) affects deepwater oxygen availability, nutrient cycling and trophic linkages.     

Climatic niche breadth determines the response of bumblebees (<Emphasis Type="Italic">Bombus</Emphasis> spp.) to climate warming in mountain areas of the Northern Iberian Peninsula

Studies examining species range shifts in the face of climate change have consistently found that response patterns are complex and varied, suggesting that ecological traits might be affecting species response. However, knowledge of how the traits of a species determine its response to climate change is still poorly understood. Here we investigate the role of species-specific climate niche breadth in forecasting bumblebee (Bombus spp.) responses to regional climate warming in the Cantabrian Range (north-western Iberian Peninsula). Climate niche breadth was defined using known data for occurrences of specific species at their continental (i.e., European) scale of distribution. For each bumblebee species, climate niche breadth was found to be related to (1) the elevational range shifts of species between their historical (1988–1989) and recent (2007–2009) distribution and (2) the variation in the climatic conditions of the localities they inhabited (i.e., the local climate space) between both study periods. Our results show a strong relationship between climate niche breadth, particularly thermal niche breadth, and the response of bumblebee species to climate warming, but only when this response was determined as variations in local climate space. The main conclusions of our work are thus twofold. First, variations in the climatic conditions underlying range shifts are useful in making accurate assessments of the impact of climate change on species distributions. Second, climate niche breadth is a particularly informative ecological trait for forecasting variations in species responses to climate change.     

The interplay among intraspecific leaf trait variation,niche breadth and species abundance along light and soil nutrient gradients

It is assumed that widespread, generalist species have high phenotypic variation, but we know little about how intraspecific trait variation (ITV) relates to species abundance and niche breadth. In the temperate rainforest of southern Chile, we hypothesized that species with wide niche breadth would exhibit 1) high among‐plot ITV, 2) a strong relationship between trait values and the environment, and 3) a close fit between traits and local environment trait optima. We measured leaf functional traits (leaf area, LMA, leaf N and P concentrations) of saplings in woody species, and compared the relative abundance of each species with its niche breadth, measured as the range of light, soil N and P availability. We used the slope of the linear regression of species’ trait–environment relationships to assess the strength and direction of these relationships, and measured the degree to which species’ trait values track the environmental optimum across plots. In some cases, species having wide niche breadth had high ITV in leaf N and also matched traits (LMA and leaf P) to local optima along the light gradient; they also had high ITV in general and matched leaf P to local optima along the soil P gradient. The relationship between species with wide niche breadth and the strength of intraspecific trait–environment relationships was generally weak and varied depending on the niche dimension and trait in question. Species varied considerably in the strength of trait–environment relationships and total magnitude of ITV, and this variation was not generally strongly related to species abundances or niche breadth patterns. In conclusion, trait variation at the community level is not driven by a few abundant, widely distributed species, but depends on the aggregate trait responses of both abundant and rare species. This makes it difficult to scale individual species trait responses up to the community level.     

Temperature and zooplankton size structure: climate control and basin‐scale comparison in the North Pacific

The global distribution of zooplankton community structure is known to follow latitudinal temperature gradients: larger species in cooler, higher latitudinal regions. However, interspecific relationships between temperature and size in zooplankton communities have not been fully examined in terms of temporal variation. To re‐examine the relationship on a temporal scale and the effects of climate control thereon, we investigated the variation in copepod size structure in the eastern and western subarctic North Pacific in 2000–2011. This report presents the first basin‐scale comparison of zooplankton community changes in the North Pacific based on a fully standardized data set obtained from the Continuous Plankton Recorder (CPR) survey. We found an increase in copepod community size (CCS) after 2006–2007 in the both regions because of the increased dominance of large cold‐water species. Sea surface temperature varied in an east–west dipole manner, showing the typical Pacific Decadal Oscillation pattern: cooling in the east and warming in the west after 2006–2007. The observed positive correlation between CCS and sea surface temperature in the western North Pacific was inconsistent with the conventional interspecific temperature–size relationship. We explained this discrepancy by the geographical shift of the upper boundary of the thermal niche, the 9°C isotherm, of large cold‐water species. In the eastern North Pacific, the boundary stretched northeast, to cover a large part of the sampling area after 2006–2007. In contrast, in the western North Pacific, the isotherm location hardly changed and the sampling area remained within its thermal niche throughout the study period, despite the warming that occurred. Our study suggests that while a climate‐induced basin‐scale cool–warm cycle can alter copepod community size and might subsequently impact the functions of the marine ecosystem in the North Pacific, the interspecific temperature–size relationship is not invariant and that understanding region‐specific processes linking climate and ecosystem is indispensable.     

Non-linear relationship between body size of terrestrial carnivores and their trophic niche breadth and overlap

Studying food partitioning of mammalian predators is important for understanding trophic structures and interactions between coexisting carnivore species. This is particularly pertinent in the light of expanding ranges of populations of generalist species whose habitat and diet overlap with more specialized species. Here, we tested the resource partitioning hypothesis in terrestrial carnivores, predicting that trophic niche breadth and overlap relate positively to body mass. We used dietary data from 18 terrestrial carnivore taxa in four families (Canidae, Mustelidae, Felidae and Ursidae; body mass 0.1–173.6 kg) in three regions in Central and Eastern Europe, i.e. deciduous forest and forest-steppe region (DFR), temperate deciduous and mixed forest region (MFR) and transitory mixed forest regions (TFR). We ranked carnivores along an axis of trophic niche (breadth and overlap), and analysed the relationship between trophic niche and body mass (or pair-wise difference in body mass). A hierarchical cluster analysis of diet composition divided carnivores into four ecological groups: wild ungulate predators; small-mammal predators; amphibians and small mammal predators and omnivores. The relationship between body mass of predators and both trophic niche breadth and trophic niche overlap were hump-shaped. The trophic niche breadth to body mass ratio was significantly lower in DFR than in TFR and trophic niche overlap was significantly higher in DFR than in MFR and TFR. The predominant food resource is small mammals whose abundance is related to local agricultural and forestry management practices. Modifications of management techniques can affect population dynamics and community composition of carnivore species, especially in the case of small-mammal predators.     

Among‐species overlap in rodent body size distributions predicts species richness along a temperature gradient

Temperature is widely regarded as a major driver of species richness, but the mechanisms are debated. Niche theory suggests temperature may affect richness by filtering traits and species in colder habitats while promoting specialization in warmer ones. However, tests of this theory are rare because niche dimensions are challenging to quantify along broad thermal gradients. Here, we use individual‐level trait data from a long‐term monitoring network spanning a large geographic extent to test niche‐based theory of community assembly in small mammals. We examined variation in body size among 23 communities of North American rodents sampled across the National Ecological Observatory Network (NEON), ranging from northern hardwood forests to subtropical deserts. We quantified body size similarity among species using a metric of overlap that accounts for individual variation, and fit a structural equation model to disentangle the relationships between temperature, productivity, body size overlap, and species richness. We document a latitudinal gradient of declining similarity in body size among species towards the tropics and overall increase in the dimensions of community‐wide trait space in warmer habitats. Neither environmental temperature nor net primary productivity directly affect rodent species richness. Instead, temperature determines the community‐wide niche space that species can occupy, which in turn alters richness. We suggest a latitudinal gradient of trait space expansion towards the tropics may be widespread and underlie gradients in species diversity.     

浙江乐清湾浮游动物空间生态位

基于2016年5月至2017年2月在乐清湾进行的4个航次浮游动物调查数据,计算乐清湾浮游动物优势种的优势度指数(S)、平均拥挤度(X*)、生态位宽度(Bi)及生态位重叠值(Qik).结果表明:乐清湾海域浮游动物优势种(S＞0.02)共17种,生态位宽度值差异较大,优势度指数与生态位宽度值呈极显著正相关.浮游动物的生态位...     

The coexistence of fish species in streams: relationships between assemblage attributes and trophic and environmental variables

Diet overlap and niche breadth are well-known species traits from trophic ecology that can assist in explaining how species interact and coexist as well as the ecological mechanisms that influence biodiversity. In the present study, we analyzed the relationships between these trophic variables and indicators of resource availability with some attributes of fish assemblages (species richness, Shannon diversity index, evenness, density and individual body size). The physical and chemical characteristics of the biotopes (topography, water quality and conservation of slopes) were examined to identify possible patterns. Monthly sampling using electrofishing was conducted in 2003 along five streams located in the Cuiabá River watershed. The relationships between environmental variables and attributes of fish assemblages were evaluated using Spearman correlation. Species richness and abundance varied among streams, with higher values (54 and 82 species) found in low-gradient streams that drained small swampy areas discharging in Cuiabá River. Diet overlap showed significant and negative correlations with species richness, the diversity index, abundance, variation in body size and food availability and positive correlations with evenness and niche breadth. Environments that had greater food availability had a reduced variety of food items (smaller amplitude) and distinct values in terms of dietary overlap. Nevertheless, to explain resource partitioning in a fish assemblage (overlap), it is necessary to consider food availability and niche breadth (degree of trophic specialization) beyond the interaction of these variables with species richness and density. In conclusion, high diversity and abundance values were strongly associated with a high degree of trophic specialization (low amplitude of trophic niche) and a small degree of overlap in the diet.     

Variable littoral‐pelagic coupling as a food‐web response to seasonal changes in pelagic primary production

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Temperature-mediated changes in zooplankton body size: large scale temporal and spatial analysis

Climate warming has been linked with changes in the spatiotemporal distribution of species and the body size structure of ecological communities. Body size is a master trait underlying a host of physiological, ecological and evolutionary processes. However, the relative importance of environmental drivers and life history strategies on community body size structure across large spatial and temporal scales is poorly understood. We used detailed data of 83 copepod species, monitored over a 57-year period across the North Atlantic, to test how sea surface temperature, thermal and day length seasonality relate to observed latitudinal-size clines of the zooplankton community. The genus Calanus includes dominant taxa in the North Atlantic that overwinter at ocean depth. Thus we compared the copepod community size structure with and without Calanus species, to partition the influence of this life history strategy. The mean community body size of copepods was positively associated with latitude and negatively associated with temperature, suggesting that these communities follow Bergmann's rule. Including Calanus species strengthens these relationships due to their larger than average body sizes and high seasonal abundances, indicating that the latitudinal-size cline may be adaptive. We suggest that seasonal food availability prevents high abundance of smaller-sized copepods at higher latitudes, and that active vertical migration of dominant pelagic species can increase their survival rate over the resource-poor seasons. These findings improve our understanding of the impacts that climate warming has on ecological communities, with potential consequences for trophic interactions and biogeochemical processes that are well known to be size dependent.     

Intraspecific trait variation across elevation predicts a widespread tree species' climate niche and range limits

Global change is widely altering environmental conditions which makes accurately predicting species range limits across natural landscapes critical for conservation and management decisions. If climate pressures along elevation gradients influence the distribution of phenotypic and genetic variation of plant functional traits, then such trait variation may be informative of the selective mechanisms and adaptations that help define climatic niche limits. Using extensive field surveys along 16 elevation transects and a large common garden experiment, we tested whether functional trait variation could predict the climatic niche of a widespread tree species (Populus angustifolia) with a double quantile regression approach. We show that intraspecific variation in plant size, growth, and leaf morphology corresponds with the species' total climate range and certain climatic limits related to temperature and moisture extremes. Moreover, we find evidence of genetic clines and phenotypic plasticity at environmental boundaries, which we use to create geographic predictions of trait variation and maximum values due to climatic constraints across the western US. Overall, our findings show the utility of double quantile regressions for connecting species distributions and climate gradients through trait‐based mechanisms. We highlight how new approaches like ours that incorporate genetic variation in functional traits and their response to climate gradients will lead to a better understanding of plant distributions as well as identifying populations anticipated to be maladapted to future environments.     

Large herbivore assemblages in a changing climate: incorporating water dependence and thermoregulation

The coexistence of different species of large herbivores (ungulates) in grasslands and savannas has fascinated ecologists for decades. However, changes in climate, land‐use and trophic structure of ecosystems increasingly jeopardise the persistence of such diverse assemblages. Body size has been used successfully to explain ungulate niche differentiation with regard to food requirements and predation sensitivity. But this single trait axis insufficiently captures interspecific differences in water requirements and thermoregulatory capacity and thus sensitivity to climate change. Here, we develop a two‐dimensional trait space of body size and minimum dung moisture content that characterises the combined food and water requirements of large herbivores. From this, we predict that increased spatial homogeneity in water availability in drylands reduces the number of ungulate species that will coexist. But we also predict that extreme droughts will cause the larger, water‐dependent grazers as wildebeest, zebra and buffalo–dominant species in savanna ecosystems – to be replaced by smaller, less water‐dependent species. Subsequently, we explore how other constraints such as predation risk and thermoregulation are connected to this two‐dimensional framework. Our novel framework integrates multiple simultaneous stressors for herbivores and yields an extensive set of testable hypotheses about the expected changes in large herbivore community composition following climate change.     

Functional diversity of crustacean zooplankton communities: towards a trait-based classification

1. While studies of phytoplankton and terrestrial plant communities have increasingly emphasised the use of functional traits in ecological research, few have yet to apply this approach to zooplankton communities.
2. This study reviews laboratory and observational studies on zooplankton feeding and life history and provides a series of functional trait tables for the North American freshwater zooplankton. Qualitative and quantitative trait tables highlight areas where data were more scarce and point to which types of studies could fill in gaps in our knowledge of zooplankton niches.
3. Data were most complete for the Cladocera across most traits, while feeding information for cyclopoids was most sparse. Qualitative data that distinguished congeneric species were lacking for most groups.
4. A regional community dendrogram for common north-eastern North American zooplankton species was generated and shows that taxonomic differences between species do not capture fully functional differences based on the traits of body length, habitat, trophic group and feeding type.
5. The data collected here, combined with readily measurable species attributes, can be used to generate a multivariate measure of the functional niche of each species found in a community. Armed with this information, functional relationships that are useful for ecological studies of lake ecosystems can be more easily conducted.     

Leaf-trait responses to environmental gradients in moorland communities: contribution of intraspecific variation,species replacement and functional group replacement

The values of many important traits of plants in a community change along environmental gradients. Such changes may involve intraspecific variation and replacement by species that have different trait values. We hypothesized that they also involve the variation within and among functional groups (FGs) to the environmental dependence of trait values at the community level. We studied environmental dependence of trait values in 27 moorlands at various scales and analyzed to what extent intraspecific variation, species replacement within FGs and FG replacement contribute to the gradient of community trait values. The community structure in moorlands was influenced mainly by two environmental factors: temperature and water condition. Plants inhabiting sites with low temperature and low-pH generally tended to have lower maximum leaf height, greater leaf mass per area, and smaller leaf size. At the community level, site-mean of maximum leaf height and leaf size generally increased with increasing temperature and water pH. Our analysis demonstrated that the relative contributions of intraspecific variation, species replacement within FGs and FG replacement differed depending on combinations of the traits and environments. The contribution of FG replacement varied considerably among cases (0.6–34.5 %). Species replacement within FGs, which has received little attention in previous studies, was most responsible for the community-level changes (31.6–65.3 %) and intraspecific variation also made a large contribution (22.9–57.9 %). Understanding such various mechanisms involving intraspecific variation and species replacement should help us better predict how the structure and functioning of moorland plant communities will respond to climate change.     

Body Size and Geographic Range Do Not Explain Long Term Variation in Fish Populations: A Bayesian Phylogenetic Approach to Testing Assembly Processes in Stream Fish Assemblages

We combine evolutionary biology and community ecology to test whether two species traits, body size and geographic range, explain long term variation in local scale freshwater stream fish assemblages. Body size and geographic range are expected to influence several aspects of fish ecology, via relationships with niche breadth, dispersal, and abundance. These traits are expected to scale inversely with niche breadth or current abundance, and to scale directly with dispersal potential. However, their utility to explain long term temporal patterns in local scale abundance is not known. Comparative methods employing an existing molecular phylogeny were used to incorporate evolutionary relatedness in a test for covariation of body size and geographic range with long term (1983 – 2010) local scale population variation of fishes in West Fork White River (Indiana, USA). The Bayesian model incorporating phylogenetic uncertainty and correlated predictors indicated that neither body size nor geographic range explained significant variation in population fluctuations over a 28 year period. Phylogenetic signal data indicated that body size and geographic range were less similar among taxa than expected if trait evolution followed a purely random walk. We interpret this as evidence that local scale population variation may be influenced less by species-level traits such as body size or geographic range, and instead may be influenced more strongly by a taxon’s local scale habitat and biotic assemblages.     

Effects of environmental warming and drought on size‐structured soil food webs

Soil systems maintain important ecosystem processes crucial for plant life and food production. Especially agricultural systems are strongly affected by climate change due to low vegetation cover associated with high temperatures and drought. Nevertheless, the response of soil systems to climate change is little explored. We used microcosms with a simplified soil community to address effects of climate change using independent temperature and dryness gradients and addressed their effects on top–down control and litter decomposition. The community consisted of maize litter as a basal resource, fungi, springtails and as top predators mites and centipedes. As the body‐size structure is of high importance for communities, we included differently‐sized springtails and predator species. After seven weeks, the experiment was terminated, and the impact of climate change on direct feeding interactions and indirect effects across trophic levels was analysed. With increasing temperature and dryness, consumption rates increased, thereby amplifying the negative influence of consumer populations on their resources. Hence, these climate‐change variables increased the top–down control of 1) predators (mainly mites) on springtails and 2) fungi on litter decomposition. In addition, we found that the climate‐change variables strengthened trophic cascades from predators on fungi whose density was thus increasingly decoupled from top–down control by their springtail consumers. Their increased decomposition rates are of high importance for carbon cycling and may result in accelerated nutrient turnover. In conclusion, our results suggest that climate change may strongly influence the structure and functioning of soil systems by strengthening consumption rates and trophic cascades, which will have far reaching consequences for the nutrient turnover and productivity of agricultural ecosystems.     

舟山长白海域主要游泳动物生态位及其分化研究

基于2016年10月（秋季）和2017年4月（春季）舟山长白海域的渔业资源调查数据,运用生态位宽度、生态位重叠及冗余分析等方法,研究了主要游泳动物的生态位,种间生态关系及生态位分化。结果显示：春、秋季主要游泳动物分别11种与8种,两季生态位宽度值差异均较大,其中春季广生态位种、中生态位种均为3种,而秋季均为2种,窄生态位种分别为5种与4种。相对重要性指数（IRI）与生态位宽度值（B_i）之间呈显著正相关。生态位重叠程度不均衡,秋季主要游泳动物的生态位重叠程度较高,O_ik > 0.6的种对数占总种对数的42.86%;春季的重叠程度较低,仅占总种对数的21.82%。RDA分析得出温度、盐度为影响主要游泳动物分布的直接因素,而溶解氧、悬浮物和pH等则为重要因素,主要游泳动物在这些资源维上存在生态分化现象。综上,分布在毗邻杭州湾口且位于著名的岱衢洋的主要游泳动物种类总体营养级较低却生态宽度值较大,大黄鱼（Larimichthys crocea）、黄姑鱼（Nibea albiflora）等一些传统的高营养级、典型特色经济种类却沦为生态位宽度极小的一般种或少有种,群落种类显著减少,资源量下降,群落结构与功能退化,稳定性下降。因此,加强游泳动物资源修复、保护与管理十分迫切且具有重要意义。     

The effects of morphology,phylogeny and prey availability on trophic resource partitioning in an anuran community

Several factors influence the partitioning of trophic resources in ecological communities, such as morphology, evolutionary history, and resource availability. Although the effects of morphology, phylogeny, and resource availability on trophic ecology have long been explored by theoretical studies, little has been done to empirically test these relationships. Here, we tested whether phylogenetic and morphological distances correlate with trophic niche overlap using a path analysis of multiple partial regression of distance matrices. Also, we tested whether niche breadth is influenced by body size using Phylogenetic Generalized Least Squares analysis. Trophic niche overlap was better explained by morphology per se than by the phylogenetic distance. We also found that predator's body size influences niche breadth calculated considering prey traits and availability, but not when we do not include these availability data. Additionally, trophic niche breadth was usually smaller when we considered prey traits and availability, differently from niche overlap, whose values increased when we did not consider these data. Our findings show that the interpretation of trophic niche in communities changes if we consider availability data, affecting inferences about coexistence and trophic specialization. Our study contributes to understanding trophic specialization and emphasizes the importance of incorporating prey availability and their traits into diet analysis.