BACKGROUND: Niche partitioning allows species to diversify resource utilisation and space allocation and reduce interspecific competition. Variations in abiotic and biotic conditions in different ecosystems may further influence resource availability and habitat utilisation, potentially reducing competition. The aim of this study is to investigate the effects of environmental variation on spatial and trophic niche overlap between two freshwater apex predators, the northern pike (Esox lucius) and the European catfish (Silurus glanis), in three different water bodies. METHODS: We used fine-scale acoustic telemetry to assess the spatial niche overlap of pike and catfish, analyzing their spatial and habitat use in relation to the thermocline and their presence in benthic versus open-water habitats. Stable isotope analysis (SIA) was used to quantify trophic niche overlap and dietary differences between the species. We compared the habitat use, spatial niche width and overlap, and trophic differentiation among waterbodies to determine how environmental conditions influence predator interactions. RESULTS: During summer, pike and catfish primarily occupied benthic habitats above the thermocline across all waterbodies and diel periods. However, catfish more frequently used open water above the thermocline, while pike were more often present in both open water and benthic habitats below it. While this general pattern of habitat use was consistent, its extent varied among lakes, suggesting that local environmental conditions shape species-specific habitat selection. Despite these variations, the species exhibited substantial spatial overlap, though its magnitude fluctuated across waterbodies and diel periods. Catfish occupied a broader spatial niche in two waterbodies, while pike had a broader niche in one. Across all lakes, catfish consistently maintained a broader trophic niche than pike. However, pike exhibited higher trophic overlap with catfish than vice versa, with nearly complete overlap in one lake and substantial but incomplete overlap in others. This suggests that pike relies more heavily on shared prey resources, while catfish exploits a broader range of food sources beyond those used by pike.These patterns were primarily driven by the position of the thermocline, prey availability, structural complexity and the greater foraging plasticity of catfish, highlighting the environmental dependence of niche partitioning in these predators. CONCLUSIONS: Our findings demonstrate that spatial and trophic niche overlaps between pike and catfish are highly context-dependent, shaped by abiotic conditions, prey availability, and species-specific foraging strategies. This study highlights the importance of integrating spatial and trophic analyses to understand predator interactions in aquatic ecosystems.
- Publication type
- Journal Article MeSH
Vertical niche partitioning might be one of the main driving forces explaining the high diversity of forest ecosystems. However, the forest's vertical dimension has received limited investigation, especially in temperate forests. Thus, our knowledge about how communities are vertically structured remains limited for temperate forest ecosystems. In this study, we investigated the vertical structuring of an arboreal caterpillar community in a temperate deciduous forest of eastern North America. Within a 0.2-ha forest stand, all deciduous trees ≥ 5 cm diameter at breast height (DBH) were felled and systematically searched for caterpillars. Sampled caterpillars were assigned to a specific stratum (i.e. understory, midstory, or canopy) depending on their vertical position and classified into feeding guild as either exposed feeders or shelter builders (i.e. leaf rollers, leaf tiers, webbers). In total, 3892 caterpillars representing 215 species of butterflies and moths were collected and identified. While stratum had no effect on caterpillar density, feeding guild composition changed significantly with shelter-building caterpillars becoming the dominant guild in the canopy. Species richness and diversity were found to be highest in the understory and midstory and declined strongly in the canopy. Family and species composition changed significantly among the strata; understory and canopy showed the lowest similarity. Food web analyses further revealed an increasing network specialization towards the canopy, caused by an increase in specialization of the caterpillar community. In summary, our study revealed a pronounced stratification of a temperate forest caterpillar community, unveiling a distinctly different assemblage of caterpillars dwelling in the canopy stratum.
- MeSH
- Biodiversity * MeSH
- Ecosystem * MeSH
- Forests MeSH
- Trees MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Geographicals
- North America MeSH
Electron paramagnetic resonance (EPR) spectroscopy represents an established tool to study properties of microenvironments, e.g. to investigate the structure and dynamics of biological and artificial membranes. In this study, the partitioning of the spin probe 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) in ex vivo human abdominal and breast skin, ex vivo porcine abdominal and ear skin as well as normal and inflammatory in vitro skin equivalents was investigated by EPR spectroscopy. Furthermore, the stratum corneum (SC) lipid composition (as determined by high-performance thin-layer chromatography), SC lipid chain order (probed by infrared spectroscopy) and the SC thickness (investigated by histology) were determined in the skin models. X-band EPR measurements have shown that TEMPO partitions in the lipophilic and hydrophilic microenvironment in varying ratios in different ex vivo and in vitro skin models. Ex vivo human abdominal skin exhibited the highest amount of TEMPO in the lipophilic microenvironment. In contrast, the lowest amount of TEMPO in the lipophilic microenvironment was determined in ex vivo human breast skin and the inflammatory in vitro skin equivalents. Individual EPR spectra of epidermis including SC and dermis indicated that the lipophilic microenvironment of TEMPO mainly corresponds to the most lipophilic part of the epidermis, the SC. The amount of TEMPO in the lipophilic microenvironment was independent of the SC lipid composition and the SC lipid chain order but correlated with the SC thickness. In conclusion, EPR spectroscopy could be a novel technique to determine differences in the SC thickness, thus suitably complementing existing methods.
- MeSH
- Abdomen MeSH
- Cellular Microenvironment MeSH
- Chromatography, Thin Layer MeSH
- Cyclic N-Oxides chemistry MeSH
- Adult MeSH
- Electron Spin Resonance Spectroscopy MeSH
- Epidermis chemistry MeSH
- Skin chemistry cytology MeSH
- Middle Aged MeSH
- Humans MeSH
- Lipids chemistry MeSH
- Young Adult MeSH
- Swine MeSH
- Breast MeSH
- Aged MeSH
- Spectrophotometry, Infrared MeSH
- Spin Labels MeSH
- Skinfold Thickness MeSH
- Ear, External MeSH
- Animals MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Aged MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Keystone mutualisms, such as corals, lichens or mycorrhizae, sustain fundamental ecosystem functions. Range dynamics of these symbioses are, however, inherently difficult to predict because host species may switch between different symbiont partners in different environments, thereby altering the range of the mutualism as a functional unit. Biogeographic models of mutualisms thus have to consider both the ecological amplitudes of various symbiont partners and the abiotic conditions that trigger symbiont replacement. To address this challenge, we here investigate 'symbiont turnover zones'--defined as demarcated regions where symbiont replacement is most likely to occur, as indicated by overlapping abundances of symbiont ecotypes. Mapping the distribution of algal symbionts from two species of lichen-forming fungi along four independent altitudinal gradients, we detected an abrupt and consistent β-diversity turnover suggesting parallel niche partitioning. Modelling contrasting environmental response functions obtained from latitudinal distributions of algal ecotypes consistently predicted a confined altitudinal turnover zone. In all gradients this symbiont turnover zone is characterized by approximately 12°C average annual temperature and approximately 5°C mean temperature of the coldest quarter, marking the transition from Mediterranean to cool temperate bioregions. Integrating the conditions of symbiont turnover into biogeographic models of mutualisms is an important step towards a comprehensive understanding of biodiversity dynamics under ongoing environmental change.
- MeSH
- Ecosystem * MeSH
- Climate * MeSH
- Symbiosis * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Climate is widely recognised as an important determinant of the latitudinal diversity gradient. However, most existing studies make no distinction between direct and indirect effects of climate, which substantially hinders our understanding of how climate constrains biodiversity globally. Using data from 35 large forest plots, we test hypothesised relationships amongst climate, topography, forest structural attributes (stem abundance, tree size variation and stand basal area) and tree species richness to better understand drivers of latitudinal tree diversity patterns. Climate influences tree richness both directly, with more species in warm, moist, aseasonal climates and indirectly, with more species at higher stem abundance. These results imply direct limitation of species diversity by climatic stress and more rapid (co-)evolution and narrower niche partitioning in warm climates. They also support the idea that increased numbers of individuals associated with high primary productivity are partitioned to support a greater number of species.
Soil microorganisms are diverse, although they share functions during the decomposition of organic matter. Thus, preferences for soil conditions and litter quality were explored to understand their niche partitioning. A 1-year-long litterbag transplant experiment evaluated how soil physicochemical traits of contrasting sites combined with chemically distinct litters of sedge (S), milkvetch (M) from a grassland, and beech (B) from forest site decomposition. Litter was assessed by mass loss; C, N, and P contents; and low-molecular-weight compounds. Decomposition was described by the succession of fungi, Actinobacteria, Alphaproteobacteria, and Firmicutes; bacterial diversity; and extracellular enzyme activities. The M litter decomposed faster at the nutrient-poor forest site, where the extracellular enzymes were more active, but microbial decomposers were not more abundant. Actinobacteria abundance was affected by site, while Firmicutes and fungi by litter type and Alphaproteobacteria by both factors. Actinobacteria were characterized as late-stage substrate generalists, while fungi were recognized as substrate specialists and site generalists, particularly in the grassland. Overall, soil conditions determined the decomposition rates in the grassland and forest, but successional patterns of the main decomposers (fungi and Actinobacteria) were determined by litter type. These results suggest that shifts in vegetation mostly affect microbial decomposer community composition.IMPORTANCE Anthropogenic disturbance may cause shifts in vegetation and alter the litter input. We studied the decomposition of different litter types under soil conditions of a nutrient-rich grassland and nutrient-poor forest to identify factors responsible for changes in the community structure and succession of microbial decomposers. This will help to predict the consequences of induced changes on the abundance and activity of microbial decomposers and recognize if the decomposition process and resulting quality and quantity of soil organic matter will be affected at various sites.
- MeSH
- Bacteria classification metabolism MeSH
- Biodiversity MeSH
- Ecosystem MeSH
- Fungi classification metabolism MeSH
- Forests MeSH
- Microbiota * MeSH
- Grassland MeSH
- Soil chemistry MeSH
- Soil Microbiology * MeSH
- RNA, Ribosomal, 16S MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Functional diversity (FD) has the potential to address many ecological questions, from impacts of global change on biodiversity to ecological restoration. There are several methods estimating the different components of FD. However, most of these methods can only be computed at limited spatial scales and cannot account for intraspecific trait variability (ITV), despite its significant contribution to FD. Trait probability density (TPD) functions (which explicitly account for ITV) reflect the probabilistic nature of niches. By doing so, the TPD approach reconciles existing methods for estimating FD within a unifying framework, allowing FD to be partitioned seamlessly across multiple scales (from individuals to species, and from local to global scales), and accounting for ITV. We present methods to estimate TPD functions at different spatial scales and probabilistic implementations of several FD concepts, including the primary components of FD (functional richness, evenness, and divergence), functional redundancy, functional rarity, and solutions to decompose beta FD into nested and unique components. The TPD framework has the potential to unify and expand analyses of functional ecology across scales, capturing the probabilistic and multidimensional nature of FD. The R package TPD (https://CRAN.R-project.org/package=TPD) will allow users to achieve more comparative results across regions and case studies.
- MeSH
- Biodiversity * MeSH
- Ecology * MeSH
- Phenotype MeSH
- Likelihood Functions MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Ecological specialization enables the partitioning of resources and thus can facilitate the coexistence of species and promote higher species richness. Specialization and niche partitioning are expected to exert a decisive influence on local spatial scales, while species richness at regional scales should be shaped mostly by historical factors and abiotic conditions. Moreover, specialization is expected to be particularly important in communities that are exceptionally species rich for their environmental conditions. Concurrently, niche overlap in these communities should be minimized to enable species coexistence. We tested these hypotheses by studying specialization-richness relationship and niche overlap in assemblages of 298 species of songbirds (Passeriformes) across Australia. We used local (2-6 ha) to regional (bioregions) spatial scales and detailed data on habitat, diet and foraging behaviour (method, substrate and stratum). We expected the richness-specialization relationship to be particularly strong (a) on local spatial scales and (b) in communities exceptionally species rich for given environmental conditions (approximated by moisture and vegetation complexity). We also expected (c) low niche overlap in assemblages with specialized species. Only the third prediction was partly supported. First, while the specialization and species richness were often positively related, the strength and the direction of the relationship changed between traits and across spatial scales. The strength of the specialization-richness relationship was consistently positive only in foraging stratum, and it increased towards smaller spatial scales only in case of habitat and diet. Simultaneously, species in local communities demonstrated high overlap in habitat and diet. Second, we did not find particularly strong specialization-richness relationships in exceptionally species-rich communities. Third, we found the expected negative relationship between specialization and overlap in foraging stratum and substrate (in local communities), suggesting that species partition ecological space locally in terms of where they find food. Our expectations were only weakly supported. Specialization on foraging stratum was probably important in facilitating species coexistence. Conversely, although species were often specialized on habitat and diet, high overlap in these traits did not preclude their local coexistence. Overall, specialization and overlap in foraging traits were more important for species coexistence than habitat or diet.
Knowledge regarding partitioning behavior and bioaccumulation potential of environmental contaminants is important for ecological and human health risk assessment. While a range of models are available to describe bioaccumulation potential of hydrophobic organic chemicals (HOCs) in temperate aquatic food webs, their applicability to tropical systems still needs to be validated. The present study involved field investigations to assess the occurrence, partitioning, and bioaccumulation behavior of several legacy and emerging HOCs in mangrove ecosystems in Singapore. Concentrations of synthetic musk fragrance compounds, methyl triclosan (MTCS), polychlorinated biphenyls, organochlorine pesticides, and polycyclic aromatic hydrocarbons were measured in mangrove sediments, clams, and caged mussels. Freely dissolved concentrations of the HOCs in water were determined using silicone rubber passive samplers. Results showed that polycyclic musks and MTCS are present in mangrove ecosystems and can accumulate in the tissues of mollusks. The generated HOC concentration data for mangrove water, sediments, and biota samples was further utilized to evaluate water-sediment partitioning (e.g., Koc values) and bioaccumulation behavior (e.g., BAF and BSAF values). Overall, the empirical models fit reasonably well with the data obtained for this ecosystem, supporting the concept that general models are applicable to predict the behavior of legacy and emerging HOCs in mangrove ecosystems.
- MeSH
- Water Pollutants, Chemical * MeSH
- Ecosystem MeSH
- Geologic Sediments MeSH
- Environmental Monitoring MeSH
- Organic Chemicals MeSH
- Polychlorinated Biphenyls * MeSH
- Polycyclic Aromatic Hydrocarbons * MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Symbiosis plays a fundamental role in nature. Lichens are among the best known, globally distributed symbiotic systems whose ecology is shaped by the requirements of all symbionts forming the holobiont. The widespread lichen-forming fungal genus Stereocaulon provides a suitable model to study the ecology of microscopic green algal symbionts (i.e., phycobionts) within the lichen symbiosis. We analysed 282 Stereocaulon specimens, collected in diverse habitats worldwide, using the algal ITS rDNA and actin gene sequences and fungal ITS rDNA sequences. Phylogenetic analyses revealed a great diversity among the predominant phycobionts. The algal genus Asterochloris (Trebouxiophyceae) was recovered in most sampled thalli, but two additional genera, Vulcanochloris and Chloroidium, were also found. We used variation-partitioning analyses to investigate the effects of climatic conditions, substrate/habitat characteristic, spatial distribution and mycobionts on phycobiont distribution. Based on an analogy, we examined the effects of climate, substrate/habitat, spatial distribution and phycobionts on mycobiont distribution. According to our analyses, the distribution of phycobionts is primarily driven by mycobionts and vice versa. Specificity and selectivity of both partners, as well as their ecological requirements and the width of their niches, vary significantly among the species-level lineages. We demonstrated that species-level lineages, which accept more symbiotic partners, have wider climatic niches, overlapping with the niches of their partners. Furthermore, the survival of lichens on substrates with high concentrations of heavy metals appears to be supported by their association with toxicity-tolerant phycobionts. In general, low specificity towards phycobionts allows the host to associate with ecologically diversified algae, thereby broadening its ecological amplitude.
- MeSH
- Ascomycota genetics growth & development MeSH
- Biological Evolution MeSH
- Chlorophyta genetics growth & development MeSH
- Ecology MeSH
- Ecosystem MeSH
- Genetic Variation MeSH
- Lichens genetics growth & development microbiology MeSH
- DNA, Ribosomal Spacer genetics MeSH
- Symbiosis genetics MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
