Niche Overlap Index Research Articles

Water Niche Characteristics of Subalpine Shrub in Eastern Qilian Mountains, China

ABSTRACTThe investigation and research of plant niche provide new ideas for understanding the extent of resource utilization by plants and the coexistence relationship among species. Taking the subalpine shrub plants in the eastern Qilian Mountains as the research object, the contribution rate of each potential water source to the shrub plants was estimated using the Bayesian mixed modelling (MixSIAR), and the spatial and temporal characteristics of their water niche were analysed quantitatively using Levins' niche breadth index and Pianka's niche overlap index. The results showed that shrub plants on the semi‐shady slope exhibited larger water niche breadth and overlap compared to those on the semi‐sunny slope, which indicated that shrub plants on the semi‐shady slope had strong adaptability to the water environment, but the competition for water among them was more intense. Furthermore, the water niche breadth and overlap of shrub plants decreased with the promotion of the growth stage, which was related to changes in precipitation and plant physiological characteristics during their growth cycle. Among the studied species, Potentilla fruticosa Linn., Salix oritrepha Schneid., Salix cupularis Rehd. and Rhododendron thymifolium Maxim. had broader water niche breadth in different habitats, indicating superior adaptability to the subalpine environment. Despite that the water niche overlap among shrub plants was high and their competition for water resources was intense, there was no absolute positive correlation between niche breadth and overlap. The research can provide a theoretical reference for the rational allocation of species during vegetation restoration in Qilian Mountain National Park.

The Ecological Niches and Interspecific Associations of the Dominant Fishes in the Xiamen Seas, China

Fish are vital in enhancing the stability of marine ecosystems. Therefore, understanding the ecological niches and interspecific correlation characteristics of their dominant species provides a good scientific basis for the protection and management of marine biodiversity. In this study, on the basis of survey data from trawls conducted in the waters off Xiamen in the spring (April) and autumn (November) of 2021, the ecotopes and interspecies connectivity of the dominant fish species were investigated using the relative importance index (IRI), χ2 tests, the association coefficient (AC), and Pearson and Spearman analyses. According to the IRI, there were 23 fish species with higher values, including 15 species in spring and 15 species in autumn. The 15 dominant fish species could be subdivided into wide-, medium-, and narrow-ecotope species, of which there were 2 and 3 wide-ecotope types in spring and autumn. The niche overlap indices exhibited a range of 0.000–0.809 in the spring and 0.000–0.915 in the autumn, showing small differences between the two seasons. The interspecific correlations between the dominant fishes in Xiamen’s waters in spring and autumn were weak, and both showed non-significant positive correlations, indicating that the correlations between the dominant fishes in this sea area are relatively independent. The findings of this investigation provide a fundamental database and theoretical framework for researching the adaptive mechanisms of marine fish in the Xiamen Seas.

Niche of woody plant populations in Picea purpurea community in the upper Taohe River

The niche of plant populations is affected by the environment, species characteristics and anthropogenic disturbance. Picea purpurea, as a major constructive species in the northeastern Qinghai-Tibetan Plateau, had been severely damaged. Although the national project for the protection of natural forests has promoted the recovery of its community, its structure, survival status, development trend, and the factors affecting it are still unclear. We selected P. purpurea communities in Zecha, Dayugou and Yeliguan forest zones at different altitudes and disturbance levels. We analyzed niche characteristics of the woody plants and the relationship between niche and altitude, and disturbance. P. purpurea has absolute advantages as a constructive species, and its population dominance and niche width in the tree layer show a decreasing trend with decreasing altitude, there is niche overlap between all species pairs. In the shrub layer, the dominant species are mostly Caprifoliaceae and Rosaceae besides P. purpurea seedlings, the proportion of species pairs with niche overlap is YLG>ZC>DYG, and all appeared niche divergence and convergence species pairs. In addition, P. purpurea seedlings had niche overlap with most woody species, and this overlap index was the highest. The mean values of the niche overlap index between species in the tree and shrub layers were all YLG>DYG>ZC. The niche overlap index between species in the tree layer was greater than that in the shrub layer in the same forest zones, indicating that the tree layer is more stable than the shrub layer, providing evidence that niche overlap maintains community stability. Regression analyses showed that minimum temperature was the main factor affecting dominance, niche, niche overlap and shrub layer species richness of the P. purpurea population. Disturbance did not significantly affect dominance and niche of P. purpurea seedling populations, but promoted niche differentiation of shrub layer species. We conclude that the P. purpurea community is mainly influenced by altitude and anthropogenic disturbance. Altitude-induced climatic variation fundamentally determines the distinct community composition and population niche. Anthropogenic disturbance has altered habitat heterogeneity and enriched community structure. Furthermore, the P. purpurea populations show a trend towards expansion. Understanding the structure and niche characteristics of P. purpurea communities on different environmental gradients enriches our ideas for implementing vegetation restoration and sustainable forest management in subalpine zones in the context of climate change, and is conducive to improving the conservation capacity of this population or community type.

Diet, feeding, and niche overlap of west coast steenbras (Lithognathus aureti) and silver kob (Argyrosomus inodorus) in the northern Benguela.

In this study, we described and compared the diet, monthly feeding intensity, and condition of west coast steenbras (Lithognathus aureti) and silver kob (Argyrosomus inodorus) caught at a unique habitat in the northern Benguela. Stomach contents of 179 west coast steenbras and 114 silver kob caught from October 2020 to September 2022 were investigated. The peak in feeding intensity of west coast steenbras appeared to be opportunistic during winter and summer periods depending on food availability. The fish condition, however, peaked at the beginning (October) and at the end (April) of the austral summer spawning period, with the hepatosomatic index (HSI) at 1.5% and the condition factor (CF) at 0.022%. Seven prey taxa were found in the diet of west coast steenbras (bivalves, bony fishes, other mollusks, algae, crustaceans, cnidaria, and polychaetas) and six taxa in the diet of silver kob (bivalves, crustaceans, bony fishes, algae, starfish, and zooplankton), indicating generalist feeding behavior in both the species. The bivalves were the most important prey items in the diet of west coast steenbras (95.9% index of relative importance [IRI]). The most important prey items in the diet of silver kob were crustaceans (83.1% IRI) and bony fishes (16.0% IRI). Crustaceans were most important in the diet of small-to-medium-sized silver kob, whereas bony fishes were most important in the diet of larger silver kob(>75 cm), with significant differences of IRI% by size class. Schoener's index of niche overlap indicated a relatively low overall niche overlap (0.11) between west coast steenbras and silver kob. This allows them to coexist as their feeding habits allow them to occupy unique niches in the coastal reef and sandy habitat and reduce competition for resources.

Dietary habits of fishing cats in a human-dominated wetland in Coastal Thailand

Abstract. Wongson T, Khaewphakdee S, Mongkonsin W, Serieys LEK, Wong W-M, Yindee M, Pattanarangsan R, Suksavate W, Promkuntod P, Klakhaeng C, Sukmasuang R. 2024. Dietary habits of fishing cats in a human-dominated wetland in Coastal Thailand. Biodiversitas 25: 2788-2797. Fishing cats, intimately connected to wetland habitats, face an escalating threat from human activities and environmental change. With its significant findings, this study offers a comprehensive insight into the dietary habits of fishing cats in a human-dominated wetland in coastal Thailand. By examining the scats of 192 fishing cats (Prionailurus viverrinus Bennett 1833) and the remains of 328 prey items, we detailed the fishing cat's diet and assessed its seasonality. Consequently, we identified 16 prey species consumed by fishing cats during the study period. The primary prey was fish, followed by rodents, birds, Indo-Chinese rat snakes (Ptyas korros (Hermann Schlegel 1837)), insects, crabs, and snails. The most crucial prey was the climbing perch (Anabas testudineus Bloch 1792) (n=69), followed by bandicoot rats (Bandicota indica Bechstein, 1800) (n=54), domestic chicken (Gallus gallus Linnaeus 1758) (n=48), and snakehead murrel (Channa striata Bloch 1793) (n=38). The niche breadth index indicated the highest specialization during the summer, while the dietary diversity index was 0.44, 0.52, and 0.38 during the summer, rainy, and winter seasons, respectively. Seasonal variations in dietary composition were not statistically significant. The niche overlap index was 0.95 between the summer and the rainy season, 0.91 between the rainy season and winter, and 0.87 between the summer and winter. These findings, with their direct implications for the conservation of fishing cats, highlight the urgent need for effective land-use management in species preservation.

Impacts of locust feeding on interspecific relationships and niche of the major plants in Inner Mongolia grasslands

Oedaleus decorus asiaticus (O. asiaticus), the dominant species of steppe locust, plays a crucial role in driving the dynamic changes of the grassland ecosystem. However, there are a limited number of studies on the impact of locust feeding on the relationship of the major plants in the species community. This study has employed the Shannon-Wiener index, Pianka index, and the maximum information coefficient (MIC) to assess the impact of O. asiaticus feeding on the community structure and interspecific relationships in the grasslands of Inner Mongolia. The chosen indices measured niche breadth, niche overlap, and interspecies correlation. The topological network structure between the main species was further analyzed. The results indicated that: 1) locust gnawing expands the niche width of major species and increases the niche overlap index of food-loving species; 2) the feeding of locusts reduces the overall correlation between species but increases the interspecific relatedness between food-loving species and other species. 3) the number of links in the species topological network structure is reduced due to locust gnawing.

Correlation of plasticities to drought and shade: implications for environmental niche overlap in drylands

Phenotypic plasticity can increase the extent of the environmental gradient occupied by a species (niche breadth) and modify the portion of niche space shared among co‐occurring species (niche overlap). Thus, phenotypic plasticity may play a role in community assembly processes. Given that plants deal with a multivariate environment, and that functional traits are often correlated, plastic responses to different environmental factors are likely correlated. However, the implications of correlations of plasticities for niche overlap remain unexplored. Here, we present and evaluate a conceptual framework that links correlations of plasticities and niche overlap patterns among co‐occurring plant species. We specifically tested in an arid shrubland whether positive, negative, or null correlations between plasticity to light and water availability would be associated with patterns of high, low, or random niche overlap, respectively. Field data identified light and water availability as key factors shaping herbaceous plant community structure. We estimated species' niche breadth and niche overlap using two‐dimensional kernel–density estimations (NOK) and standardised effect sizes of Pianka's niche overlap index (OSES). We measured phenotypic plasticity to light and water availability in the six most abundant species in a greenhouse experiment. We used the plasticity index (PI) to test 1) the relationship between plasticity to light and water availability, and 2) the association between overall plasticity (average PI across traits) and niche breadth. We found a positive relationship between plasticity to light and water availability. Increased overall plasticity was associated with a broader niche breadth. Both NOK and OSES estimations indicated a significant niche overlap pattern. Results supported one of the predictions of our conceptual framework: that a positive correlation of plasticities would lead to increased niche overlap. The verified conceptual framework broadens our understanding of the role of phenotypic plasticity in plant community coexistence.

Unravelling the modes of action of autochthonous staphylococci against Aspergillus westerdijkiae and the antiochratoxigenic effect in dry-cured ham

Aspergillus westerdijkiae is well known for its capacity to produce high amounts of ochratoxin A (OTA) in dry-cured ham. Some autochthonous microorganisms, such as Staphylococcus xylosus FHSCC Sx8 and Staphylococcus equorum FHSCC Se31 have antifungal effect and can be used as biocontrol agents (BCAs) to reduce the OTA contamination. The aims of this work were to reveal their modes of action against A. westerdijkiae MUM 16.142 in a dry-cured ham model system and validate the antifungal effect in dry-cured ham. As well as to assess the effect of live cells, dead cells, and cell-free broth; the pattern of nutrient use, the niche overlap index (NOI), interactions by dual culture assays, the antifungal activity of volatile compounds, and their effect on the fungal proteome. Both cocci in the dual-culture assay were able to decrease the A. westerdijkiae growth, but only S. xylosus reduced the OTA production at 20 °C. Moreover, changes in the abundance of proteins related to cell wall integrity, secondary metabolite production and carbohydrate metabolism were observed. Furthermore, the anti-A. westerdijkiae effect of S. xylosus was validated in dry-cured ham since this coccus was able to reduce the OTA production in this meat product.

Seasonal Prey Abundance and Food Plasticity of the Vulnerable Snow Leopard (Panthera uncia) in the Lapchi Valley, Nepal Himalayas.

Conservation strategies for apex predators, like the snow leopard (Panthera uncia), depend on a robust understanding of their dietary preferences, prey abundance, and adaptability to changing ecological conditions. To address these critical conservation concerns, this study presents a comprehensive evidence on prey availability and preferences for snow leopards in the Lapchi Valley in the Nepal Himalayas from November 2021 to March 2023. Field data were collected through the installation of twenty-six camera traps at 16 strategically chosen locations, resulting in the recording of 1228 events of 19 mammalian species, including domesticated livestock. Simultaneously, the collection of twenty snow leopard scat samples over 3800 m above sea level allowed for a detailed dietary analysis. Photo capture rate index and biomass composition analysis were carried out and seasonal prey availability and consumption were statistically analyzed. A total of 16 potential prey species for the snow leopard were documented during the study period. Himalayan musk deer (Moschus leucogaster) was the most abundant prey species, but infrequent in the diet suggesting that are not the best bet prey for the snow leopards. Snow leopards were found to exhibit a diverse diet, consuming eleven prey species, with blue sheep (Pseudois nayaur) being their most consumed wild prey and horses as their preferred livestock. The Pianka's index of dietary niche overlap between the summer and winter seasons were 0.576, suggesting a pronounced seasonal variation in food preference corroborating with the prey availability. The scarcity of larger preys in winter is compensated by small and meso-mammals in the diet, highlighting the snow leopard's capacity for dietary plasticity in response to the variation in resource availability. This research suggests for the utilization of genetic tools to further explore snow leopard diet composition. Additionally, understanding transboundary movements and conducting population assessments will be imperative for the formulation of effective conservation strategies.

An environmental habitat gradient and within-habitat segregation enable co-existence of ecologically similar bird species.

Niche theory predicts that ecologically similar species can coexist through multidimensional niche partitioning. However, owing to the challenges of accounting for both abiotic and biotic processes in ecological niche modelling, the underlying mechanisms that facilitate coexistence of competing species are poorly understood. In this study, we evaluated potential mechanisms underlying the coexistence of ecologically similar bird species in a biodiversity-rich transboundary montane forest in east-central Africa by computing niche overlap indices along an environmental elevation gradient, diet, forest strata, activity patterns and within-habitat segregation across horizontal space. We found strong support for abiotic environmental habitat niche partitioning, with 55% of species pairs having separate elevation niches. For the remaining species pairs that exhibited similar elevation niches, we found that within-habitat segregation across horizontal space and to a lesser extent vertical forest strata provided the most likely mechanisms of species coexistence. Coexistence of ecologically similar species within a highly diverse montane forest was determined primarily by abiotic factors (e.g. environmental elevation gradient) that characterize the Grinnellian niche and secondarily by biotic factors (e.g. vertical and horizontal segregation within habitats) that describe the Eltonian niche. Thus, partitioning across multiple levels of spatial organization is a key mechanism of coexistence in diverse communities.

Deciphering Staphylococcus xylosus and Staphylococcus equorum mode of action against Penicillium nordicum in a dry-cured ham model system

Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.

Niche and Interspecific Association of Dominant Tree Species in Spruce–Fir Mixed Forests in Northeast China

This study focuses on the natural coniferous and broad-leaved mixed forest dominated by Picea asperata and Abies fabri in the Jingouling Forest Farm of Northeast China. Specifically, we place emphasis on examining the effects of different thinning intensities. By comparing the niche characteristics and interspecific associations of dominant tree species under various thinning intensity conditions, our aim is to gain deeper insights into the patterns of resource utilization by species and the interplay of tree species in the forest canopy. Based on plot survey data, analysis methods such as niche breadth, niche overlap index, Pearson correlation coefficient, and Spearman’s rank correlation coefficient were used to analyze the niche and interspecific relationship characteristics of the dominant tree species in the community. The results indicate that among the four selective cutting intensities, the tree species with the highest importance value in all cases is Abies fabri, with an average importance value of 30.29%. Additionally, Picea asperata exhibits the widest niche breadth among the tree species, with a value of 4.59. The selective thinning in this study resulted in a reduction of average species niche overlap in the community compared to the control plots. There were both positive and negative interspecies associations observed, but they were statistically insignificant. Few pairs showed significant correlations, with the positive-to-negative ratio of Pearson coefficients decreasing as the selective cutting intensity increased. The Spearman rank correlation analysis revealed a positive-to-negative ratio exceeding one for species pairs in the community under both light and heavy-cutting conditions, with no significant negative correlations observed. In summary, selective cutting disturbance can effectively increase the importance value of the dominant tree species, Abies fabri, in the community. However, it leads to a reduction in the niche breadth of all tree species present in the forest. Moderate selective cutting is considered a more suitable intensity, as it promotes the maintenance of biodiversity and yields higher forest management benefits in the mixed forest of Picea asperata and Abies fabri in Northeast China.

Niche and interspecific association of dominant tree species in karst forest of Junzi Mountain, Eastern Yunnan, China.

To understand the interspecific relationships of tree species in the karst forest of Junzi Mountain in Eas-tern Yunnan, we evaluated the niche and interspecific association of dominant tree species based on field survey plot data with the combining approaches of niche determination, χ2 test, association coefficient (AC), and Spearman rank correlation test. The results showed that the niche breadth of Quercus glaucoides was the largest and that of Juglans mandshurica was the smallest. The ranking of niche breadth was more consistent with the ranking of frequency than with that of importance values. The degree of niche overlap was generally low, with a mean value of 0.21, suggesting a low similarity in resource utilization among tree species. The overall association of dominant tree species was significantly positive, and the ratio of positive and negative association was 1.07, indicating that the communities were at a relatively stable and the late succession stage. The χ2 test and Spearman rank correlation test for tree dominant species showed that 65.3% species pairs were not significantly associated with each other, indicating a weak interspecific association. Both association coefficient (AC) and Spearman rank correlation coefficient showed significantly positive correlations with the corresponding niche overlap index. The species pairs of Q. glaucoides-Rhamnella martini, Viburnum propinquum-Zanthoxylum myriacanthum, Cladrastis delavayi-Carrierea calycina, Z. myriacanthum-C. delavayi had strong interspecific associations and wide ecological niches, thus may have potential application value in ecological restoration of karst region in eastern Yunnan and the vicinity areas.

Morphological characteristics influence the spatial mixing patterns of shorebirds at Shengjin Lake.

The coexistence of species with similar ecological niches is one of the core interests of community ecology research. However, how functional feeding traits, including bill size and leg length, determine the niche of mixed flocks of shorebird species has seldomly been studied, as well as, microhabitat variables affect the spatial patterns of availability and the quality of patches for wintering. From October 2016 to March 2017 at Shengjin Lake, Anhui Province, China, we recorded 226 scan samples from the different microhabitats and 93 focal animal videos of four common shorebird species: common greenshank, spotted redshank, Kentish plover, and little ringed plover. We found that the species participating in the mixed groups were different in each microhabitat. The results of the overlap index for microhabitats and foraging techniques between the species were consistent with the morphological characteristics of these species. Kentish and little ringed plovers had the highest Pianka's niche overlap index values of 0.95 and 0.98 for microhabitats and foraging techniques, respectively, whereas common greenshank and spotted redshank had values of 0.78 and 0.89, respectively. Common greenshank and spotted redshank used four foraging techniques: a single probe (PR), multiple probes (MPR), a single peck (PE), and multiple pecks (MPE). Kentish and little ringed plovers only used PE and MPE. The mean bill size, mean leg length, and mean foraging frequency were significantly associated with water depth. The mean bill size and mean leg length were both significantly correlated with the mean foraging frequency of shorebirds. The vegetated area was the most important variable for grouping among shorebirds. We concluded that the four species showed differences in their preferred microhabitats and foraging patterns. Interspecific morphological differences, including bill and leg lengths, resulted in niche differentiation. Thus, effective resource allocation by regional species was realized, and a dynamic balance was achieved by the mixed foraging species. The information on foraging behavior and habitat requirements could be useful in the management of water levels in natural areas and conservation of a diversity of wintering shorebirds.

Interspecies Association and Community Stability of Plants in the Core Distribution Area of Thuja sutchuenensis

The protection of endangered species is a hot topic for scholars worldwide, and interspecific association and community stability analysis are important methods with which to explore the structure and function of the endangered species community. Thuja sutchuenensis Franch. is an endangered species; however, studies on the T. sutchuenensis community remain insufficient. Here, based on the data of the plot survey of the T. sutchuenensis community in the Ta-pa Mountains and Xuebao Mountains, we analyzed the interspecific associations, niche width, and niche overlap of major species in the arborous and shrub layers, as well as community stability. The results showed that the overall interspecies association between the species of the arbor layer was non-significantly negatively associated, while the shrub layer was non-significantly positively associated. The Chi-square test results showed that the species pairs without interspecific association in the arbor layer and the shrub layer were much higher than those with significant interspecific association; in other words, the interspecific association of species in the T. sutchuenensis community was loose. The results of interspecific association coefficient analysis showed that the number of negatively associated species pairs was significantly higher than that of positive association species pairs, but Pearson’s correlation coefficient and Morisita’s niche overlap index analysis showed that the degree of competition between species in the community was small. In the arbor layer, the niche width of T. sutchuenensis was the widest, while in the shrub layer, the niche width of T. sutchuenensis was relatively high, indicating that T. sutchuenensis had a strong ability to adapt to the environment and use available resources. In addition, the intersection point of community stability (32.11, 67.89) in the vegetative community of T. sutchuenensis suggested that the community displayed a better stability. The survival strategy of T. sutchuenensis is based on its strong adaptability to the harsh environment to escape the competition among species, and this knowledge can provide a reference for the protection and restoration of endangered species.

Diet composition and interspecific niche of Taohongling Sika deer (Cervusnipponkopschi) and its sympatric Reeve's muntjac (Muntiacusreevesi) and Chinese hare (Lepussinensis) in winter (Animalia, Mammalia).

Species co-existence depends on how organisms utilize their environment and resources. Little is known about the winter diet composition and sympatric co-existence of South China sika deer and its companion species in Taohongling. In this study, high-throughput sequencing and metabarcoding trnL were used to study the diet composition and interspecific relationship including sika deer, Reeve's muntjac, and Chinese hare. Our results show that 203 genera in 90 families are contained in the diet of sika deer, 203 genera in 95 families for Reeve's muntjac, and 163 genera in 75 families for Chinese hare. Sika deer fed on Rubuschingii, Loropetalumchinense, and Euryajaponica in winter, accounting for 75.30%; Reeve's muntjac consumed mainly R.chingii, E.japonica, and Euonymusgrandiflorus, accounting for 68.80%, and Chinese hare mainly fed on R.chingii, Smilaxchina, and Rhuschinensis, accounting for 41.98%. The Shannon index showed no significant difference between groups (p > 0.05). The NMDS analysis found considerable overlap among three species. Sika deer and Reeve's muntjac consumed similar forage plants but varied greatly in Chinese hare, which occupied the widest choice in winter, resulting in higher diet breadth and increased dietary divergence, thereby reducing competition and facilitating coexistence. The diet niche overlap index among them, as represented by Pianka's index, ranging from 0.62 between sika deer and Chinese hare to 0.83 between sika deer and Reeve's muntjac, which indicated a more similar niche and potential competition in closely related species. Our findings provide a new diet perspective of three herbivores, leading to a more comprehensive understanding of resource partitioning and species coexistence.

Habitat and trophic niche overlap among juvenile black sea bass, tautog, and cunner: interspecific interactions amid a species geographic range expansion

Juvenile black sea bass Centropristis striata populations are increasing in southern New England estuaries of the northeastern USA with possible trophodynamic effects on labrid species: tautog Tautoga onitis and cunner Tautogolabrus adspersus. In this study, we examined the abundance, size-structure, and feeding ecology of juvenile sea bass and labrids in Narragansett Bay (Rhode Island, USA) from June to October in 2018 and 2019 and evaluated potential interspecific competition using habitat, diet, and isotopic niche overlap indices. Juveniles (age-0+) of each fish species spatiotemporally co-occurred in shallow, polyhaline habitats throughout the estuary. Age-0 cohorts were numerically dominant across species and initially recruited to the study area in July (minimum total length, TL = 15-20 mm), reached peak abundances in mid- to late summer (maximum abundances = 12-140 fish 100 m-2), and emigrated from field sites in October (maximum TL = 85-96 mm). Stomach content and stable isotope (δ15N and δ13C) analyses determined that focal fishes were generalist carnivores that foraged in bentho-pelagic food webs. Fishes also overlapped in their respective ambit and core isotopic niche space, but interspecific dietary overlap was size-dependent. Dietary overlap was most pronounced between sea bass ≤49 mm TL and labrids ≤59 mm TL due to their mutual reliance on gammarid and caprellid amphipods. Ontogenetic dietary shifts then resulted in food niche segregation, such that sea bass 50-139 mm TL consumed decapod crustaceans and fish, whereas labrids 60-181 mm TL mainly fed on amphipods, worms, bivalves, and turf-associated biota, i.e. bryozoans, hydroids, and seaweeds. Habitat and trophic niche overlap between early juvenile sea bass and labrids purportedly have not caused opposite population trajectories or food resource limitation in Narragansett Bay, indicating an absence of exploitative competition. Alternatively, realized competition between species may be too spatiotemporally restricted to alter their population dynamics. Continuous monitoring of the sea bass’s bio-ecological effects in southern New England estuaries is warranted, however, given their recent range expansion and increasing abundances at northern latitudes.

Status of Barbodes binotatus (Valenciennes, 1842) in ecological trophy in the Ciliwung River Region, West Java

B.binotatus is native fish from Ciliwung River whose existence is decreasing due to the similarity of food sources between native species and introduced species, causing competition to seek food. The study aimed to determine the trophic level and position B. binotatus in the Cilliwung River ecosystem based on gut content analysis using the purposive sampling method during August-October 2021. Data were obtained from a total of 60 samples from the Ciesek River, Cirangrang, and Sukabirus. The fishes were dissected, and gut contents were observed using a light microscope, with observations repeated 3 times for each sample. Data analysis includes the relative length of gut, index of preponderance, nichce area, niche overlap, and trophic level of an organism. The feed source consists of Bacillarophyta (68.62%), Chlorophyta (16.40%), Manogononta (8.41%), Cyanophyta (2.81%), Euglenaphyta (1.70%), Amoebozoa (1.01%), Copepods (0.93%), and detritus (0.11%). The result showed that B. binotatus in Ciliwung River is at trophic level II and included as an omnivore (2.1 < Troph < 2.9). B. binotatus is as an omnivore and have a common food source with introduced species, causing competition to seek food.

Stomach Content Analysis for Juvenile Great Hammerhead Sharks Sphyrna mokarran (Rüppell, 1837) from the Arabian Gulf

The stomach contents of 30 male and 43 female (age &lt; 3 years; 74–236 cm total length) juvenile great hammerhead sharks (Sphyrna mokarran (Rüppell, 1837)) obtained from commercial fisheries operating in Saudi Arabian waters of the Arabian Gulf were analyzed for the first time. After exclusion of parasites and abiotics, a total of 31 prey items, including the remains of cephalopods, fish, crustaceans, and bivalve mollusks, were identified in the stomachs of 59 great hammerheads. Based on the index of relative importance, teleosts were their main prey, and Platycephalus indicus (Linnaeus, 1758) was the most important prey at the species level. Significant age-related dietary differences were noted (F = 1.57, p = 0.026), indicating that the prey of the hammerheads aged 0–3 years shifted from Platycephalidae to Myliobatidae. Levin’s niche overlap index was low (0.05–0.21), indicating that &lt;3-year-old juvenile great hammerheads are specialized predators. The estimated trophic level was 4.40–5.01 (mean ± SD, 4.66 ± 0.45), indicating that the great hammerhead is a tertiary consumer.

Mapping the changing distribution of two important pollinating giant honeybees across 21000 years

Pollinators play an important role in ecosystems, but global climate change threatens the diversity and geographical distribution of pollinators. Bees are some of the most important pollinators and are particularly sensitive to climate change and environmental change. Apis laboriosa and Apis dorsata are two species of giant honeybees distributed in Asia, and play important roles in their ecosystems. In this study, we analyzed the key factors affecting the distribution of two species, as well as their potential suitable areas and possible co-existence regional changes under the global climate change. We collected and filtered global distribution data of A. laboriosa and A. dorsata, then used eight climatic variables and Community Climate System Model version 4 (CCSM4) to simulate their potential suitable areas for the past, present and future (using two different climate scenarios) using MaxEnt. Finally, we used ArcGIS 10.2 and ENMTools to calculate range overlap and niche overlap of the two species in order to infer areas of co-existence. Temperature-related variables had the largest contribution to the model simulation. Among these variables, temperature seasonality (Bio 4) and mean temperature of coldest quarter (Bio 11) showed the strongest influence on the distributions of two giant honeybees. Under the current climate scenario, the species overlap in Nepal and Yunnan of China, with low niche overlap index. Between the last-glacial maximum to the present both honeybees moved northwest to their present range. A. laboriosa is projected to move to the northeast and A. dorsata may move southeast. Only 6.6% of overlapping distribution is currently protected, and further work is needed to protect these key areas.