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Despite supporting a disproportionately large fraction of the global biodiversity, freshwater ecosystems are ranked as the most highly threatened habitats ahead of both terrestrial and marine ecosystems. Furthermore, many regions are still characterized by limited knowledge on taxonomy and ecology of freshwater fishes. The need for ecological information in understudied regions is important particularly where there are recent discoveries of new species and unique lineages and for threatened and endangered taxa that require conservation management.This study evaluated the trophic ecology of two freshwater fish species Sandelia bainsii and Amatolacypris trevelyani that are both classified as endangered in the International Union for Conservation of Nature (IUCN) Red List. These two species, which are narrow‐range endemics in the Eastern Cape, South Africa, comprise allopatric lineages whose ecology is poorly known. This study used stable isotope analysis to evaluate the food web patterns, explore the trophic niche dynamics and estimate the prey source contributions for the two species in different headwater habitats.The fishes isotopic niche sizes were spatially variable, suggesting the likely importance of stochastic variation in resource availability and probable interspecific interactions. The three lineages within S. bainsii exhibited low isotopic niche overlap onto those of sympatric fishes in most habitats. Isotopic mixing model revealed that these lineages' diets were mostly dominated by gatherers/collectors. In comparison, the two lineages within A. trevelyani exhibited high niche overlap with other species and generally had variable diets.Despite the low and high niche overlap patterns of S. bainsii and A. trevelyani, respectively, the isotopic niche overlap patterns of co‐occurring species onto those of the former suggest the likely lack of competitive hierarchies. The trophic niche patterns of these two endangered species helped to shed some light on the potential invasion risks by non‐piscivorous fishes with opportunistic feeding habits, which could exert competitive interspecific interactions. [ABSTRACT FROM AUTHOR]

The plant pathogenic fungus Cytospora is notoriously known for causing woody plant canker diseases, resulting in substantial economic losses to biological forests and fruit trees worldwide. Despite their strong negative ecological impact, the existing and prospective distribution patterns of these plant pathogens in China, according to climate change, have received little attention. In this study, we chose three widely dispersed and seriously damaging species, namely, Cytospora chrysosperma, Cytospora mali, and Cytospora nivea, which are the most common species that damage the Juglans regia, Malus domestica, Eucalyptus, Pyrus sinkiangensis, Populus spp., and Salix spp. in China. We utilized ecological niche modeling to forecast their regional distribution in China under four climate change scenarios (present, SSP 126, SSP 370, and SSP 585). The results show that temperature-related climate factors limit the current distribution ranges of the three species. Currently, the three studied species are highly suitable for northeast, northwest, north, and southwest China. Under future climate scenarios, the distribution ranges of the three species are projected to increase, and the centers of the adequate distribution areas of the three species are expected to shift to high-latitude regions. The three species coexist in China, primarily in the northwest and north regions. The ecological niches of C. chrysosperma and C. nivea are more similar. The distribution range of C. mali can reach the warmer and wetter eastern region, whereas C. chrysosperma and C. nivea are primarily found in drought-prone areas with little rainfall. Our findings can help farmers and planners develop methods to avoid the spread of Cytospora spp. and calculate the costs of applying pesticides to reduce contamination and boost yields. [ABSTRACT FROM AUTHOR]

The South American tomato leaf miner Tuta absoluta is an economically important pest that recently invaded Africa, Asia, and Europe. The rapid spread and failure to predict suitable areas in the invaded range have concerns about whether this species underwent a niche shift during the biological invasion. In this study, we (i) reconstructed the dispersal routes of T. absoluta, (ii) tested if this species had undergone niche shift, (iii) and evaluated the consequences for predictions of ecological niche models. The two-dimensional centroid shift, overlap, unfilling, and expansion (COUE) framework and the n-dimensional hypervolume framework (NDH) were applied to compare the native and invasive niches. The reconstruction of the dispersal routes of T. absoluta showed that the species initially invaded highly suitable areas and further spread to regions with non-analogous climate conditions. This analysis also revealed a structured dispersal pattern and the frequent occurrence of long-dispersal events, indicating that trade and transport of goods played a key role in the spreading of this pest. Niche analysis showed divergent results depending on the framework considered. According to the COUE framework, the native and invasive niches of T. absoluta are equivalent, but the NDH framework indicates that both niches are divergent. The fact that the model developed with native and invasive occurrence outperformed the model built using only native occurrence records corroborates the hypothesis of niche shift. Our findings contribute to understanding the factors related to the rapid spread of T. absoluta and can be applied to prevent the introduction of other potential invaders. [ABSTRACT FROM AUTHOR]

In fast-flowing streams, caddisfly larvae are responsible for processes that collectively determine the efficiency with which the detritivore community is able to decompose autochthonous and allochthonous detritus. This ecosystem function ensures high water quality and represents a precious service for resident rural communities. The analysis of δ13C and δ15N in eight caddisfly taxa from a mid-mountain stream evidenced a remarkable complementarity in their feeding preferences. An aquatic moth mimicking the caddis mode of life was also included in the survey and its feeding niche appeared to be in between the one of caddis taxa. Moderate niche overlap was interpreted in terms of low functional redundancy, implying that in case of a reduction in diversity, no taxon could be a perfect substitute for another, with a loss of functional efficiency. Low redundancy could be caused by niche segregation due to avoidance of competition/interference between taxa. The broad range of δ13C and δ15N described in this study warns against attributing single δ13C and δ15N to Trichoptera as a group, or even to single families. These results contribute to the still poorly known distribution of East African caddisflies and to the characterisation of feeding preferences of Afrotropical trichopteran larvae. [ABSTRACT FROM AUTHOR]

Context. Invasive vertebrates have significant negative impacts on biodiversity and agricultural production worldwide. Increased connectivity among countries, through trade and tourism, is escalating the rate of introductions of vertebrate species, particularly herpetofauna, across international borders. In Australia, Asian black-spined toads (ABSTs; Duttaphrynus melanostictus) are one of the species most intercepted at borders. They are considered a biosecurity risk because of the potential for negative environmental impacts, similar to those caused by cane toads (Rhinella marina). Aims. We aimed to compare ABSTs with cane toads to investigate potential impacts and distribution of ABSTs in the Australian context. We also aimed to identify knowledge gapsregarding ABST biology and the potential role of cane toads in an ABST invasion in Australia. Methods. We undertook a literature review to obtain published data to compare the life history characteristics of ABSTs and cane toads. We also modelled climatic niche overlap and compared suitable habitat for both species in Australia. Key results. Ourresults show ABSTs and cane toads have broadly similar reproductive life histories and feeding niches. In particular, similarities include large clutch sizes, preferred oviposition sites, and diet at tadpole and adult life stages. In Australia, the species share suitable potential habitat, particularly in North Queensland, where the majority of ABST incursions have occurred. The species differ in size, call characteristics, clutch size relative to body size, and egg development rate, although the environment also influences these traits. We identify gaps in our knowledge of ABST spatial ecology, thermal tolerances, water reliance, and habitat. Conclusions. ABSTs pose a significant biosecurity threat to Australia. Similarities in life history to cane toads means they may have similar impacts, but may have a more limited distribution in Australia. Invasion of Australia by ABSTs would likely result in interactions with cane toads, but it is not possible to accurately determine the outcomes of those interactions without further investigation. Implications. Addressing knowledge gaps and quantitatively determining the potential for competition between ABSTs and cane toads will assist surveillance and response planning for ABST incursions in Australia. [ABSTRACT FROM AUTHOR]

The drivers behind plant‐pollinator interactions still need to be fully understood. Previous research has suggested that observed interactions result from either neutral interaction between species based on their abundance or from niche‐based processes, which are reflected in the adaptations of both plants and pollinators. Furthermore, the importance of both scenarios can differ depending on seasonal dynamics translated into differences in resource availability. Extensive research has been conducted on New‐World hummingbirds (Trochilidae), whereas much less is known about Old World nectar‐feeding sunbirds (Nectariniidae). Our study aimed to explore whether sunbird‐plant interactions are explained by neutral and/or niche‐based processes. Thus, we tested the effects of abundance, morphology, and nectar sugar content on the observed interactions and the link between sunbirds and plant traits. Moreover, we explored the effects of robbing on these mechanisms. Finally, we investigated the partitioning of bird pollination niches, based on floral traits. We used a dataset of sunbird‐plant interactions collected at Mount Cameroon during two seasons (dry and wet seasons). Our study shows that sunbird‐plant interactions are influenced by both neutral and niche‐based processes. Neutral processes and nectar reward were the main mechanisms underlaying the observed interactions in the dry season. However, as more ornithophilous plants bloom during the rainy season, morphological trait‐matching becomes more important. We found a correlation between bill length and floral tube dimensions and observed niche overlap among the sunbird species. Considering this and other research, we suggest that plant‐pollinator interactions are influenced by a combination of both neutral and niche‐based processes. [ABSTRACT FROM AUTHOR]

A simple model that can assess the river rehabilitation using rehabilitation potential index (RPI) of fish habitat has been developed. This model calculates the RPI using three indicators: the habitat suitability index (HSI), niche breadth (NB), and niche overlap (NO). These indicators were estimated by using environmental factors that affect fish habitat in the river and then RPI was obtained by combining the indicators. However, the model showed some limitations. For example, the representative NO was obtained by summing each NO, which does not reflect the difference of the number of fish species in rivers. This study improved the estimation method of NO by using the averaged NO that can consider different kinds of species in each river. In addition, the previous study used standardization method for making three indicator values in the range of 0 to 1. However, the standardized indicators can distort the relative size when we compare with the original data. In this study, we have selected alternative methods to calculate indicators, eliminating the need for standardization. Along with these improvements, this study developed a new RPI estimation model by reviewing various methods and selecting the proper ones. The RPIs of the two models were estimated using fish abundance and habitat environmental factors from 57 sites in Han river, Geum river, and Nakdong river in Korea. We compared the results of the existing model with the new model using root mean square error (RMSE) and mean absolute deviation (MAD). The new model showed the reduced uncertainty and enhanced applicability in comparison to the previous model.

The ability of community species to adapt to the environment and use resources and the importance of species in the ecological system in time and space are generally represented by ecological niche. In order to study the niche characteristics and dynamic changes of the dominant species in the arbor layer of the 4hm2Pinus tabuliformis-Quercus wutaishansea mixed forest sample plot in Lingkong Mountain,and to gain a better understanding of the competition and coexistence among species in the sample plot, this study was conducted based on a typical community investigation. Four indices of important value, niche width, niche overlap, and niche similarity were chosen to calculate and analyze the niche characteristics and examine dynamic changes over a period of 10 years from 2011 to 2021. The results showed that: (1) In 2021, the important values for Quercus wutaishansea and Pinus tabuliformis were 19.906 and 13.906, respectively.The niche widths were 0.962 and 0.555, which showed difference compared to those in 2011. Both were much larger than other species, indicating that they occupied an absolutely dominant position in the community. (2) The mean values of niche overlap and similarity of dominant species in the arbor layer of the Lingkong Mountain sample plot have both increased over the past 10 years. Additionally, the species pairs with the highest overlap and similarity values have changed, suggesting an intensification of competition among these species.

Abstract An increasingly globalised world has facilitated the movement of non‐native species (NNS) via the poorly regulated international pet trade. While focus is increasingly being placed on preventative action to combat invasive NNS—often cheaper and less difficult than the management of established populations—successful prevention requires controlling potential pathways and obtaining baseline knowledge of species' availability. Here we performed an in‐depth analysis of the freshwater pet trade as one major vector of NNS, compiling its species inventory and deriving threats of NNS release and establishment in the wild. With Germany as our study region, we surveyed pet stores, websites and the country's largest online classified portal, eBay Kleinanzeigen, recording the taxa encountered. For each species, we determined the likelihood of release based on availability and price (cheaper and/or more readily available species have been shown to be of greater risk), and the likelihood of establishment based on ecological niche breadth and niche overlap with environmental conditions in Germany. The survey revealed 669 species, of which 651 were non‐native to Germany. Looking at release likelihood, more readily available species in pet stores and on websites proved to be cheaper. For websites, there was a significant effect of occurrence status (i.e. released, not released, native) on price, with released and native species being significantly cheaper. Species previously released in Germany and elsewhere demonstrated greater niche breadths and greater niche overlaps between their source regions and Germany; and for species released in Germany, there was a significantly positive relationship between the magnitude of niche overlap and the number of documented occurrences. Finally, we combined our release and establishment likelihood findings under ‘Release Risk’ metrics to highlight the species most worthy of prioritisation. We propose these metrics as proactive methods for screening species in the trade, which can inform future policy direction and intervention. Read the free Plain Language Summary for this article on the Journal blog.

The global focus on fostering harmonious interactions and promoting rational coexistence among wildlife species to uphold or reinstate biodiversity remains a prominent area of interest. We conducted a study on the sable and yellow-throated marten in Taipinggou National Nature Reserve, Heilongjiang, China, using the line transect method and infrared camera traps from 2022 to 2023. We then analyzed the overlap of their suitable habitats and niches with the aim of gaining insight into the interspecific competition between these two species. We found that the suitable habitat areas for the sable and yellow-throated marten were 55.20 km2 and 23.28 km2, accounting for 24.86% and 10.48% of the total area of this study, respectively. The overlap between the suitable habitats for the sable and yellow-throated marten was 15.73 km2, accounting for 28.5% and 67.6% of their suitable habitat, supporting our Hypothesis 1. The first principal component (Dim1) of the niche explained 35.4% of the overall variability, which is mainly related to the environmental variables “Distance from Settlements” and “Distance from Roads”. Overall, 25.5% of the total variability was explained by the second principal component (Dim2), associated with “Slope” and “Distance from Coniferous and Broadleaved Mixed Forest”. The niches occupied by the sable and yellow-throated marten were both off-center of the environmental background space, with the niches of the sable being larger than those of the yellow-throated marten. Schoener’s D index was 0.56, indicating a high degree of niche overlap between the sable and yellow-throated marten, supporting our Hypothesis 2. Our study is helpful in terms of formulating conservation and management policies for the sable and yellow-throated marten.

Wild ungulates play crucial roles in maintaining the structure and function of local ecosystems. The alpine musk deer (Moschus chrysogaste), white-lipped deer (Przewalskium albirostris), and red serow (Capricornis rubidus) are widely distributed throughout the Nyenchen Tanglha Mountains of Tibet. However, research on the mechanisms underlying their coexistence in the same habitat remains lacking. This study aimed to investigate the mechanisms underlying the coexistence of these species based on their dietary preferences through DNA barcoding using the fecal samples of these animals collected from the study area. These species consume a wide variety of food types. Alpine musk deer, white-lipped deer, and red serow consume plants belonging to 74 families and 114 genera, 62 families and 122 genera, and 63 families and 113 genera, respectively. Furthermore, significant differences were observed in the nutritional ecological niche among these species, primarily manifested in the differentiation of food types and selection of food at the genus level. Owing to differences in social behavior, body size, and habitat selection, these three species further expand their differentiation in resource selection, thereby making more efficient use of environmental resources. Our findings indicate these factors are the primary reasons for the stable coexistence of these species.

This study contributes to filling knowledge gaps regarding recent information on the diet of the European hake, Merluccius merluccius Linnaeus, 1758, in the Greek seas, particularly its ontogenetic shifts and its spatiotemporal variability. The trophic preferences of M. merluccius were investigated in the North Aegean Sea during the summers of 2019 to 2023 with visual stomach content analysis to assess its composition, diversity, and variability across body-size classes, years, and subareas. The identified prey are functionally diverse and in many cases also primary targets for local fisheries. The ontogenetic trophic niche of hake was characterized by two distinct shifts, delineated by 10 and 50 cm body-size thresholds. Cephalopods were a prevalent dietary component for large hake individuals. The intermediate body-size classes demonstrated greater trophic niche breadth concerning prey diversity and absolute prey-size ranges. A feeding strategy characterized by the specialization of individuals was also revealed. The effect of the temporal and spatial context on the hake diet was occasionally correlated with spatiotemporal variations in the sizes of their populations. In conclusion, ontogenetic and spatiotemporal variability in the hake diet were found to be significant and should be considered in the data collection design and analyses of the trophic interactions of the species.

In order to reveal the status of habitat resource utilization and the degree of competition among lichens in Dabancheng mountainous areas. In this work, 30 plots were sampled in the field and the species cover data of the plots were investigated, and the niche characteristics and environmental factors of lichen community species were analyzed by using niche width, niche overlap index and ordination analysis in this Dabancheng mountainous area. The results were as follows: (1) The niche width of Rusavskia elegans and Circinaria contorta were the widest in Dabancheng mountainous area, indicating that they were more adaptable to different environments. The niche widths of other lichen species were narrow, indicating that the species used the environmental resources to a less extent. (2) The niche overlap value between species was generally low, with only a few species pairs having a high niche overlap value. The degree of niche differentiation between lichen species was high, indicating that the competition between species was not intense. (3) Although niche overlap was common among species with wider niche widths, niche overlap values were lower. However, some species with narrower niche widths had higher niche overlap values with other species. As a result, there was no clear linear relationship between niche overlap and niche width. (4) The distribution of lichen species varied along the altitudinal gradient, and altitude, light intensity, humidity, wind speed, and human disturbance were the dominant environmental factors for the different niche characteristics of lichen community species in the study area. In conclusion, as a result of habitat resource competition in Dabancheng mountainous area, lichen species occupied their own distinct niches, resulting in niche differentiation and relatively stable communities. The distribution of species differed significantly due to differences in habitat conditions along the altitudinal gradient. The results of this paper provides a theoretical basis for the study of lichen community assembly, which are of great significance to the conservation of lichen species diversity and habitat in the region.

Abstract The relationship between spatial distribution and phylogeny has been widely debated in recent decades. To understand biogeographic and evolutionary history relationships and to explore the interspecific similarities and phylogenetic correlations of niche characteristics, we collected and recorded all distribution points for eight species of rhubarb on the Qinghai‐Tibet Plateau, used different methods to describe the ecological niche, and explored the relationship between phylogeny, ecological niche, and distribution range. The results reveal that: (1) the ranges of optimal environmental variables for species with close kinship are not exactly the same, ecologically similar species are not necessarily sister species, and the overlap of rhubarb has no significant correlation with phylogeny. Therefore, the impact of ecological dimensions on species formation is greater than that of geographical latitude for the eight species of rhubarb. (2) Among the eight species of rhubarb, the breadth of ecological niche is positively correlated with the current suitable habitat area and negatively correlated with fluctuations in future suitable habitat area. In the future, except for Rheum tanguticum and Rheum palmatum, the suitable planting areas for the other six species of rhubarb will decrease as greenhouse gas emissions concentrations and time increase. Therefore, species with smaller ecological niches are at a greater risk of habitat loss compared to species with larger ecological niches. (3) In both existing and future distribution prediction models of rhubarb, we observed that both the widely distributed Rheum spiciforme and the niche narrow Rheum nobile, all eight species of rhubarb are present in the Hengduan Mountains, based on our analysis, we propose that the Hengduan Mountains should be regarded as a priority conservation area for rhubarb, to preserve the species' biodiversity. Our study lays the groundwork for identifying evolutionary trends in ecological specialization.

Abstract Understanding how functionally similar species segregate resources to minimize competition is vital for predicting evolutionary factors and patterns of coexistence. We conducted a study in Mata de Itamacaoca, in the middle Munim River basin, Maranhão, northeastern Brazil, to characterize the functional morphology and trophic niches of five coexisting Characiform species in this area - including a recently described species, and to investigate whether their functional morphology is a key determinant of their trophic niches. Our analysis of functional morphology and diet, employing linear measurements to predict dietary specializations, showed that these species are predominantly generalist insectivores with a significant morphological overlap. This study underscores the influence of species' natural history on their ecological characteristics, contributing to more effective conservation strategies.

In the framework of polyploidization, a widely discussed issue is the possibility of niche shift. Numerous studies have investigated niche differentiation among cytotypes, with some confirming distinct differences, while others finding them to be similar. Within this research project, we focus on the case of the cytotypes (2x and 4x) of Festuca amethystina L. and the closely related F. tatrae (Czakó) Degen (2x). We hypothesize that a significant change in the edaphic niche of tetraploids could be a factor that enabled them to occupy new lowland areas inaccessible to diploids which are characteristic of mountain habitats.The edaphic niche differentiation between Festuca amethystina cytotypes was determined by studying the niches’ breadths using PCA-based modeling and separate analyses of particular soil features. The modeling was based on SoilGridsTM data, and the conclusions were compared with the results of the direct soil studies. Such a research model makes it possible to determine to what extent the data coming from the mentioned database allows for the indication of niche differentiation.Coarse-grained modeling based on SoilGridsTM data indicated a significant change in the edaphic requirements of the tetraploids, as well as pointed to the niche shift towards a higher content of sand, lower carbon and nitrogen content, and lower pH. The direct soil sampling and laboratory tests confirmed these trends and provided a more detailed understanding of the cytotypes requirements. However, no statistically significant differences were observed between cytotypes concerning soil pH, the majority of base cations, available forms of phosphorus and potassium, and the results of CHN elemental analysis. While the direct soil sampling did not reveal significant differences, the analyses based on the niche modeling, considering a wide background area in Central Europe (using SoilGrids data), captured significant variations. This comprehensive approach allowed us to uncover a highly logical pattern of niche shift, which indicates that tetraploids are predisposed to extend their geographical range to post-glacial lowland areas.Additionally, Festuca amethystina tetraploids display a wider edaphic niche breadth than their closely related and hypothetical ancestor Festuca tatrae. The decision to include the latter reduced the probability that the obtained result of the significant increase of the tetraploid edaphic niche was a simple result of hybridization.

Knowing the determinants of biodiversity is crucial to understanding the differentiation of living organisms. Several gene-flow limiting processes can drive divergence, including adaptive ecological differentiation or geographical isolation both constituting environmental-dependent reproductive barriers. Furthermore, the strength of these processes may be associated to the degree to which ecological niches are conserved and shared by phylogenetically related species. Here, we aim to disentangle these two alternatives reproductive barriers by evaluating the degree of ecological niche similarity among phylogenetically related species. We performed ecological niche modelling (ENM) on four species belonging to a recently diversified genus (Aquilegia, Ranunculaceae) occurring in montane environments of the Alpine and Apennine chains (southern Europe). Results show that niche differentiation among species is related to phylogenetic distinctiveness. Nevertheless, niche similarity tests indicated that the conditions selected by the species are more similar than expected from the null models, even though they are sparsely available in the respective ecological spaces, suggesting that the observed pattern may result from phylogenetic niche conservatism. These results, highlight that paleogeographic events in south-European mountains may have driven divergence by isolation in Aquilegia while partially retaining the possibly ancestral characters of the niches. [ABSTRACT FROM AUTHOR]

Aim: Eurasian grapevine (Vitis vinifera), one of the most important fruit crops worldwide, diverged from its wild and currently endangered relative (V. vinifera ssp. sylvestris) about 11,000 years ago. In the 19th century, detrimental phylloxera and disease outbreaks in Europe forced grapevine cultivation to use American Vitis species as rootstocks, which have now become naturalized in Europe and are starting to colonize similar habitats to the wild grapevine. Accordingly, wild grapevine now faces two additional threats: the expansion of vineyards and invasive rootstocks. Furthermore, climate change is expected to have significant impacts on the distribution of all grapevines in Europe. In this study, we quantified the distributional and bioclimatic overlap between grapewine's wild relative and the taxa associated with viticulture, under current and future climate. Location: Europe, North America. Methods: The distributions of wild Eurasian grapevine, cultivated Eurasian grapevine and five American grapevine species used in rootstock breeding programs were linked to climate variables to model their bioclimatic niches. These ecological niche models were used to quantify the spatial and bioclimatic overlap between these seven Vitis taxa in Europe. Results: Niche and spatial overlap is high between the wild, cultivated and rootstock grapevines, suggesting that existing conflicts between vineyards and wild grapevine conservation may be further complicated by naturalized rootstocks outcompeting the wild grapevine, especially under future scenarios of climate change. In the hottest scenario, only 76.1% of the current distribution of the Eurasian grapevine remains in suitable area. Main Conclusions: As wild grapevine may ultimately provide a valuable gene pool for adapting viticulture to a changing world, these findings demonstrate the need for improved management of the wild grapevine and its natural habitat, to counteract the harmful effects of global change on the wild relatives of viticulture. [ABSTRACT FROM AUTHOR]

The impoundment of the Yangtze River and construction of the Three Gorges Dam and Reservoir created an unnatural flow regime with a 30 m water-level fluctuation and four artificial seasons that differ from the river's natural flow-regime timing. Using stable isotopes, we selected 15 common benthic fish species representing five trophic guilds to analyze seasonal variation in production sources, trophic niche width, and niche overlap. We hypothesized that, similarly to a natural flow regime, artificial hydrological seasons effectively influence fish trophic niches. We found consistency in seasonal shifts in the contribution of aquatic and terrestrial producers to fish biomass. δ13C and δ15N depicted seasonal changes in intra-guild trophic niche width and intra- and inter-guild niche overlap. Considering that the Three Gorges Reservoir's flow regime is artificially regulated, our findings suggest that water-level fluctuation is one of the key mechanisms driving such trophic shifts and allowing multiple species to coexist. Given the increased cascaded large reservoir construction and the concomitant creation of unnatural flow regimes in large rivers worldwide, these findings are timely. Our findings contribute to improving water-level management by optimizing rhythmicity while balancing flood control and fish protection. [ABSTRACT FROM AUTHOR]

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In the Anthropocene era, understanding the impact of climate change on niche shift, species distribution, and habitat change is increasingly important for the conservation of biodiversity. In this respect, species distribution models have been considered an important tool over the last decade. The present study illustrates distributional change, niche dynamics and climatic shifts of Saraca asoca (Roxb.) De Wilde in India, a proven medicinal plant and a listed threatened species by IUCN, under different climate change scenarios using MaxEnt. The robustness of the model was satisfactory (AUC = 0.936), indicating a good fit. There could be a significant gain in suitable habitat between the present and future scenarios, ranging from a minimum of 52,275.17 km² (RCP 2.6) to a maximum of 95,994.62 km² (RCP 4.5). In the future, the suitable habitat range would shift towards colder regions of India, where cultivation of S. asoca could be taken up, thus enabling effective management of the natural habitat and population of the species. This study will help understand the effects of climate change on S. asoca and its implications for conservation of the species. [ABSTRACT FROM AUTHOR]

Sympatric species may overlap in their use of habitat and dietary resources, which can increase competition. Comparing the ecological niches and quantifying the degree of niche overlap among these species can provide insights into the extent of resource overlap. This information can be used to guide multispecies management approaches tailored to protect priority habitats that offer the most resources for multiple species. Stable isotope analysis is a valuable tool used to investigate spatial and trophic niches, though few studies have employed this method for comparisons among sympatric marine turtle species. For this study, stable carbon, nitrogen, and sulfur isotope values from epidermis tissue were used to quantify isotopic overlap and compare isotopic niche size in loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp's ridley (Lepidochelys kempii) turtles sampled from a shared foraging area located offshore of Crystal River, Florida, USA. Overall, the results revealed high degrees of isotopic overlap (>68%) among species, particularly between loggerhead and Kemp's ridley turtles (85 to 91%), which indicates there may be interspecific competition for resources. Samples from green turtles had the widest range of isotopic values, indicating they exhibit higher variability in diet and habitat type. Samples from loggerhead turtles had the most enriched mean δ34S, suggesting they may forage in slightly different micro‐environments compared with the other species. Finally, samples from Kemp's ridley turtles exhibited the smallest niche size, which is indicative of a narrower use of resources. This is one of the first studies to investigate resource use in a multispecies foraging aggregation of marine turtles using three isotopic tracers. These findings provide a foundation for future research into the foraging ecology of sympatric marine turtle species and can be used to inform effective multispecies management efforts. [ABSTRACT FROM AUTHOR]

In 2009, 2015 and 2021, we carried out a quadrat survey of plant communities in 9 plots of Xiejiadian landslide in Yinchanggou. Then, Shannon niche width formula and Pianka niche overlap formula were used to calculate the dynamic changes of niche width and niche overlap of dominant species in plant community. The results showed that: (1) The niche width of the photophilous species decreased gradually, while the niche width of the shade tolerant species and the fertilizer-liking species increased gradually. (2) There was a significant linear positive correlation between the niche width of dominant species and the average value of their niche overlap. The species with larger niche width had better fitting effect, while the species with smaller niche width were more dispersed. (3) On the whole, the total niche width, average niche width and average niche overlap of each layer of the community were increasing continuously, while the average niche overlap of herb layer decreased in 2021 due to niche differentiation. The study revealed the characteristics and changes of plant community structure in the process of restoration of landslide in the past 13 years after the earthquake, and provided a reference for the related research of vegetation restoration and the development of soil and water conservation work after the earthquake. [ABSTRACT FROM AUTHOR]

Aim: Allopatric speciation is the primary mode of diversification in the Mediterranean Basin. However, the contribution of climatic adaptation during this process is contradictory. In this work, we investigate the eco‐evolutionary processes that drove diversification in this region, using European vipers as a case study. We describe the climatic requirements of different lineages to compare their responses to the Pleistocene climatic oscillations and tackle the evolutionary mechanisms underlying their diversification. Location: Eurasia and North Africa. Taxon: European vipers (genus Vipera). Methods: We used ecological niche modelling (ENM) to identify the climatic requirements of 24 Vipera lineages and infer past range dynamics associated with their diversification during the Pleistocene. To test whether climatic niches varied across lineages, we calculated the phylogenetic signal of different climatic variables and examined the relationship with phylogenetic relatedness. To investigate climatic niche evolution and test for phylogenetic niche conservatism (PNC), we quantified pairwise niche overlap in sister phylogenetic units under a 3D hypervolume approach. Results: ENM identified temperature annual range, precipitation of wettest month and precipitation of driest quarter as the most important climatic variables related to the distribution of most lineages, validating Pelias clade as cold‐adapted, and Vipera 1 and Vipera 2 as warm‐adapted clades. Projections to past conditions varied among clades, with Pelias and Vipera 1 having more similar responses, while Vipera 2 exhibited greater variability. We found significant phylogenetic signal in one temperature‐related and two humidity‐related climatic variables and detected high complexity in ecological niche evolution across the phylogeny, both rejecting the hypothesis of PNC. Main Conclusions: Climatic adaptation played a significant role in driving diversification among European vipers. Cold‐adapted and warm‐adapted lineages presented similar climatic requirements and remarkable responses to Pleistocene stages, resulting in an intricate pattern of niche divergence along the phylogeny that favours local adaptation rather than PNC. [ABSTRACT FROM AUTHOR]

Aim: The widely observed positive response of productivity to biodiversity, known as the biodiversity‐productivity relationship (BPR), underpins nature‐based solutions for mitigating and adapting to global changes. Little is known of the role of such emergent processes in the restoration of damaged ecosystems. Here, we test for evidence of a BPR in degraded freshwater lakes, and its role in underpinning or undermining lake recovery from eutrophic states. Location: Lower Yangtze and Huaihe river basins, China, East Asia. Taxa: Freshwater phytoplankton; also macrophytes, fish, zooplankton and zoobenthos. Methods: A systematic review of biodiversity studies was conducted to enumerate freshwater biodiversity change during eutrophication, encompassing 572 samples from 155 lakes in East China. Empirical samples were then taken of 93 phytoplankton communities from 38 lakes in ecologically degraded states of eutrophication. Samples were analysed for niche overlap in relation to biodiversity and productivity, and metrics of network structure indicative of community stability. Results: Reviewed publications on eutrophication in East China lakes revealed losses in biodiversity of macrophytes, fishes, zooplankton and zoobenthos but not phytoplankton. Empirically sampled eutrophic lakes maintained high phytoplankton biodiversity through niche differentiation, and phytoplankton biodiversity correlated positively with biomass, in line with the expectations of BPR. Conclusions: The positive effect of biodiversity on phytoplankton productivity in eutrophic lakes acts in opposition to the negative impacts on productivity induced by eutrophication‐management strategies of nutrient suppression. In degraded systems, the BPR contributes to sustaining productivity of lake phytoplankton communities, impeding recovery from a eutrophic state. This is a case of the BPR playing an undesirable role at the ecosystem level. Lake recovery programmes need to anticipate that the control of phytoplankton biomass will depend on reducing nutrients to a level sufficient to degrade the internal structure of the phytoplankton community. [ABSTRACT FROM AUTHOR]

Aim: Quantifying niche shifts of non‐native species and their interactions with natives is vital in evaluating invasion risk yet remains difficult. Climate filtering and competition with native congeners are two important processes impacting niche changes and yielding contradictory predictions for the coexistence of non‐native and native species. Closely related species representing the Eastern Asia (EA)–Eastern North America (ENA) floristic disjunction provide a powerful yet unexplored system for assessing the relative roles of these two processes. Here, we tested three niche change scenarios (unfilling, expansion and stable) using EA species naturalized in ENA. We aim to answer: (1) which scenario is observed for naturalized species? and (2) how has niche overlap between EA and ENA congeners changed after naturalization? Location: ENA and EA. Time Period: Present. Major Taxa Studied: Angiosperms. Methods: Niches were estimated using both occurrences and predictions generated by ecological niche models. Niche changes of naturalized species and their niche overlap with natives were measured using Schoener's D. Contributions of niche expansion and unfilling on niche changes of naturalized niches were evaluated using hierarchical partitioning and linear regressions. We further measured pairwise phylogenetic distances among EA and ENA congeners and evaluated the association with niche overlap. Results: Unfilling‐dominated postintroduction niche changes of the naturalized species. EA species naturalized in ENA exhibited lower niche overlap with ENA native congeners compared with native range populations in EA. These results remain when considering time since introduction and potential physical dispersal limitations interpreted by projecting suitable niche space between EA and ENA. However, dispersal limitation may contribute to the degree of niche unfilling. Main Conclusions: Using intercontinental disjunct species as a study system, we found that naturalization is shaped jointly by climate filtering and competition with native congeners, providing valuable insights for evaluating invasion risk underlying global floristic exchanges. [ABSTRACT FROM AUTHOR]

Simple Summary: The snow leopard is an apex predator, residing in mountain ecosystems in Asia. This study was conducted in the Lapchi Valley of the Nepal Himalayas between November 2021 and March 2023 to investigate the seasonal variations in its prey availability and selectivity. Through camera traps and scat analysis, we identified the blue sheep, Himalayan musk deer, domestic horse, and sheep as key prey species for snow leopards. Snow leopards exhibited dietary diversity, consuming eleven prey species, with blue sheep as their primary wild prey and horses as preferred livestock. Seasonal variation in food preference was noted, where small mammals filled the nutritional requirements during winter's prey scarcity. The study recommends genetic tools for further diet analysis and stresses the importance of transboundary research and population assessments in shaping effective conservation strategies. 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. [ABSTRACT FROM AUTHOR]

Freshwater systems are among the most affected by the introduction of exotic species. The pumpkinseed sunfish Lepomis gibbosus, a centrarchid native to eastern North America, is listed among the top ten introduced freshwater fishes with the greatest ecological impact globally. Despite this, genetic and evolutionary studies of the species are still scarce. Here, we analyzed the genetic variability of introduced populations of L. gibbosus using three mitochondrial genes (COI, d-loop, and ND1). In addition, we used species distribution modeling to compare the niche of introduced versus native populations to assess the present and potential future distribution of the species under different climate change scenarios. Compared with the native populations, introduced ones present a lower level of genetic variability, indicating these populations originated from a small number of individuals from the native (Atlantic) population in the USA and Canada. The low variability was likely driven by a founder effect and subsequent bottleneck, as often occurs in invasive species. Our modeling results suggest not only that L. gibbosus modified its niche during the invasion process in Europe but also the possible global expansion of the species under future climatic conditions, which could facilitate its establishment in almost all continents. [ABSTRACT FROM AUTHOR]

The segregation in one trophic niche of n -dimensional niches can allow many species to coexist in the same habitat. In this study, we conducted surveys in Ben En National Park, Thanh Hoa Province, Vietnam to examine stomach contents of two syntopic tree frog species, Hyla simplex and Polypedates megacephalus , using the stomach-flushing method. A total of 21 individuals of H. simplex and 32 individuals of P. megacephalus were sampled revealing 352 food items (H. simplex : 131 invertebrates belonging to 20 prey types of seven orders; P. megacephalus : 215 invertebrates belonging to 22 prey types of 11 orders). Generally, both species consumed slightly diverse and equal prey types. However, ants (Formicidae) and termites (Rhinotermitidae) were identified as the most dominant and important prey for the two tree frog species. With only 38.95% overlap, it is evident that there is tropic segregation between the two syntopic species. [ABSTRACT FROM AUTHOR]

Understanding ecological niches is essential to comprehend the processes that allow similar species to occur sympatrically. Niche overlap can result in some degree of competition when resources are limited, and therefore, sympatric species must differ to some extent at some niche level in order to co-exist. The two trawling bats that co-occur along the Mediterranean region share their foraging strategy and feeding grounds, potentially consuming similar prey species. However, no research has been conducted to elucidate their dietary niche similarities or differences to test whether these may shape their sympatric foraging occurrence and distribution. We used DNA metabarcoding to study the dietary composition and niche overlap of Myotis capaccinii (an exceptionally endangered species) and M. daubentonii (a relatively common species) during the breeding season in northeastern Iberia. Unlike previous studies, Trichoptera was the most frequently consumed prey order for both bat species, followed by Diptera (mainly Chironomidae). We also report, for the second time, fish consumption by M. capaccinii in the Iberian Peninsula, and provide the fourth report of piscivory for European bats. Although minor differences in diet composition between both trawling bats were found, they presented highly overlapping dietary niches and similar dietary niche breadths, suggesting that they exploit similar trophic resources. Overall, the current results suggest that both species may have found a balance to co-occur in the same foraging niche without interspecific competition being a limiting factor. [ABSTRACT FROM AUTHOR]

Larvae of Urania moths feed exclusively on Omphalea plants, which are widely distributed in the Neotropics. However, the distributions of the two Urania species in this region are disjunct. This distributional pattern could derive from the presence of the Andes, but it could also be related to differences in ecological niches, the presence of negative interactions, or the absence of conditions that can only be observed at a habitat level. We tested whether differences in the ecological niches of continental Urania moths play a role in their disjunct distribution. Using species records and climatic variables, we characterized the ecological niches of Urania moths and their host plants and analyzed the overlap of the moths' niches. Using ecoregions as a proxy of habitat-level environmental conditions, we explored the role of host plant availability on the moth distributions. Suitable conditions for the species were widespread, with a lack of suitability mostly restricted to the Andean highlands. The two moth distributions were closely related to that of their host plants. There was medium-high overlap of niche models when available conditions were considered; however, niche overlap was not found to be statistically significant. Our results corroborate the barrier effect of the Andes on the dispersal of these moths, but they also show that niche differences contribute to the disjunct distributions of U. fulgens and U. leilus. Furthermore, other non-climatic factors appear to play a crucial role in the disjunction of the species ranges in areas where overlapping suitable conditions are continuous. Our findings support speciation in Urania moths as allopatric and indicate that their disjunct distributions can be attributed to multiple factors. Other studies exploring the causes of similar distributional patterns should consider that a single factor may not be enough to explain such patterns.

Abstract Sympatric species may overlap in their use of habitat and dietary resources, which can increase competition. Comparing the ecological niches and quantifying the degree of niche overlap among these species can provide insights into the extent of resource overlap. This information can be used to guide multispecies management approaches tailored to protect priority habitats that offer the most resources for multiple species. Stable isotope analysis is a valuable tool used to investigate spatial and trophic niches, though few studies have employed this method for comparisons among sympatric marine turtle species. For this study, stable carbon, nitrogen, and sulfur isotope values from epidermis tissue were used to quantify isotopic overlap and compare isotopic niche size in loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp's ridley (Lepidochelys kempii) turtles sampled from a shared foraging area located offshore of Crystal River, Florida, USA. Overall, the results revealed high degrees of isotopic overlap (>68%) among species, particularly between loggerhead and Kemp's ridley turtles (85 to 91%), which indicates there may be interspecific competition for resources. Samples from green turtles had the widest range of isotopic values, indicating they exhibit higher variability in diet and habitat type. Samples from loggerhead turtles had the most enriched mean δ34S, suggesting they may forage in slightly different micro‐environments compared with the other species. Finally, samples from Kemp's ridley turtles exhibited the smallest niche size, which is indicative of a narrower use of resources. This is one of the first studies to investigate resource use in a multispecies foraging aggregation of marine turtles using three isotopic tracers. These findings provide a foundation for future research into the foraging ecology of sympatric marine turtle species and can be used to inform effective multispecies management efforts.

Interspecific competition is notoriously difficult to detect and quantify, especially in species that are wide-ranging or otherwise difficult to track in the wild. Research investigating interspecific competition usually relies on niche overlap measurements despite that this approach alone does not yield rigorous inference. As an illustration, we review published research assessing interspecific competition in mid-sized carnivores in North America (bobcat – Lynx rufus; Canada lynx – Lynx canadensis; coyote – Canis latrans), and report on shortcomings associated with commonly used study designs and types of inference. Niche overlap measurements typically focus on one or two resources (e.g., food, space, habitat), often using non-independent sampling units and inadequate replication. Few studies measure overlap variation through space, time, or resource variability, which is crucial for robust assessment. Niche overlap (or lack thereof) is used as evidence both for and against interspecific competition, reflecting a weak link between competition theory, predicted responses, and observations. Overall, challenges associated with conducting competition research in the field promote over-reliance on simple measurements, flawed study designs and weak inference. Minimally, niche overlap studies should include assessment across multiple niche dimensions and spatial or temporal variation in competitor density or resource availability. Dynamic investigative approaches should include new technologies for tracking inter-individual interactions, study designs that leverage quasi-experiments (e.g., decline in shared resources, biological control of one competitor), and synthetic analyses (e.g., meta-regression). Ultimately, better understanding of competition theory vis-à-vis study design and data needs will promote improved understanding of the role of interspecific competition in nature.

Assessing the foraging ecology of a threatened species is necessary to understand their movement behaviour and habitat use patterns, which are essential for developing effective protection strategies. Here, the foraging ecology of reef manta rays (Mobula alfredi) in the Chagos Archipelago, a region encompassed by a vast no-take marine protected area (MPA), was investigated using stable isotope analysis of skin and muscle tissue. Enriched δ13C values suggest the population predominantly forages in nearshore environments. Skin δ13C values increased with increased rainfall, likely associated with the boosts in primary production and zooplankton biomass due to the coastal advection of seabird guano. Annual variations in δ13C values of skin and muscle were observed and are consistent with reduced nutrient transport associated with the effects of Indian Ocean Dipole oscillations, including a deepening of the thermocline, a suppression of cold-water upwelling, and reduced rainfall. Short- and long-term foraging strategies and locations were identified by applying hierarchical clustering, isotopic niche analysis, and Bayesian stable isotope mixing models to δ13C and δ15N of paired skin and muscle tissue samples. Two isotopically distinct groups of M. alfredi were identified, employing either local foraging strategies restricted to specific locations or wide-ranging strategies that likely mean they engage in regular migrations throughout the archipelago. Ninety-eight percent of M. alfredi were estimated to switch between strategies utilising and connecting multiple discrete nearshore habitats, emphasising their role in ecosystem functioning by facilitating the transport of nutrients across ecosystem boundaries. However, illegal, unreported, and unregulated fishing and lost or abandoned fishing gear commonly occur within the MPA. Locations of particular concern are Egmont Atoll as it is a highly active aggregation location and Peros Banhos Atoll where IUU frequently occurs and M. alfredi are estimated to be heavily reliant upon for foraging. Frequent migrations between atolls by M. alfredi also raises concern over their vulnerability to these activities along migration corridors. This research bridges current knowledge gaps in this population's foraging ecology and concomitant movement patterns, which should inform conservation strategies in the region.

Nowadays, eucheumatoids lead the rankings in globally cultivated seaweed production, including the seaweeds Kappaphycus alvarezii and Kappaphycus striatus. Eucheumatoids have declined in biomass over recent years, and climate change is regarded as one of the important factors. Thus, it is urgent to investigate the range dynamics of Kappaphycus under climate change. Considering its high practical relevance for conserving biodiversity, the niche conservatism hypothesis was tested between the two species through ecological niche modeling (ENM), ordination, and hypervolume approach which quantify the extent of niche overlap. In this study, we sifted the best-performing algorithm - Maxent and tuned parameters for fitting the distribution of both Kappaphycus species, compared their geographical distribution patterns, and predicted their range dynamics under climate change. All three methodological approaches indicated significant niche differences in both geographical and environmental space between the two Kappaphycus species. Our models predicted that range shifts mainly induced by rising sea surface temperature are likely to differ between two Kappaphycus species, with K. striatus suffering much range contraction (359,448 km2 in 2100s RCP8.5). By the year 2100, both Kappaphycus species are forecast to lose suitable habitats along most of the coastline of Southeast Asia under the RCP8.5 scenario. K. alvarezii is predicted to expand its distributions (96,429 km2) under the RCP2.6 scenario by the year 2100, suggesting resilience to mild global warming. Our study enhances the understanding of Kappaphycus aquaculture, and is conducive to the sustainable development of tropical seaweed by stressing the importance of conservation and investigation under climate change.

When two putatively cryptic species meet in nature, hybrid zone analysis can be used to estimate the extent of gene flow between them. Two recently recognized cryptic species of banded newt (genus Ommatotriton) are suspected to meet in parapatry in Anatolia, but a formal hybrid zone analysis has never been conducted. We sample populations throughout the range, with a focus on the supposed contact zone, and genotype them for 31 nuclear DNA SNP markers and mtDNA. We determine the degree of genetic admixture, introgression, and niche overlap. We reveal an extremely narrow hybrid zone, suggesting strong selection against hybrids, in line with species status. The hybrid zone does not appear to be positioned at an ecological barrier, and there is significant niche overlap. Therefore, the hybrid zone is best classified as a tension zone, maintained by intrinsic selection against hybrids. While the two banded newt species can evidently backcross, we see negligible introgression and the pattern is symmetric, which we interpret as supporting the fact that the hybrid zone has been practically stationary since its origin (while extensive hybrid zone movement has been suggested in other newt genera in the region). Our study illustrates the use of hybrid zone analysis to test cryptic species status. [ABSTRACT FROM AUTHOR]

Human‐mediated species introductions provide real‐time experiments in how communities respond to interspecific competition. For example, managed honey bees Apis mellifera (L.) have been widely introduced outside their native range and may compete with native bees for pollen and nectar. Indeed, multiple studies suggest that honey bees and native bees overlap in their use of floral resources. However, for resource overlap to negatively impact resource collection by native bees, resource availability must also decline, and few studies investigate impacts of honey bee competition on native bee floral visits and floral resource availability simultaneously.In this study, we investigate impacts of increasing honey bee abundance on native bee visitation patterns, pollen diets, and nectar and pollen resource availability in two Californian landscapes: wildflower plantings in the Central Valley and montane meadows in the Sierra.We collected data on bee visits to flowers, pollen and nectar availability, and pollen carried on bee bodies across multiple sites in the Sierra and Central Valley. We then constructed plant‐pollinator visitation networks to assess how increasing honey bee abundance impacted perceived apparent competition (PAC), a measure of niche overlap, and pollinator specialization (d'). We also compared PAC values against null expectations to address whether observed changes in niche overlap were greater or less than what we would expect given the relative abundances of interacting partners.We find clear evidence of exploitative competition in both ecosystems based on the following results: (1) honey bee competition increased niche overlap between honey bees and native bees, (2) increased honey bee abundance led to decreased pollen and nectar availability in flowers, and (3) native bee communities responded to competition by shifting their floral visits, with some becoming more specialized and others becoming more generalized depending on the ecosystem and bee taxon considered.Although native bees can adapt to honey bee competition by shifting their floral visits, the coexistence of honey bees and native bees is tenuous and will depend on floral resource availability. Preserving and augmenting floral resources is therefore essential in mitigating negative impacts of honey bee competition. In two California ecosystems, honey bee competition decreases pollen and nectar resource availability in flowers and alters native bee diets with potential implications for bee conservation and wildlands management. [ABSTRACT FROM AUTHOR]

Competition shapes animal communities, but the strength of the interaction varies spatially depending on the availability and aggregation of resources and competitors. Among carnivores, competition is particularly pronounced with the strongest interactions between similar species with intermediate differences in body size. While ecologists have emphasized interference competition among carnivores based on dominance hierarchies from body size (smaller = subordinate; larger = dominant), the reciprocity of exploitative competition from subordinate species has been overlooked even though efficient exploitation can limit resource availability and influence foraging.Across North America, fishers Pekania pennanti and martens (Martes spp.) are two phylogenetically related forest carnivores that exhibit a high degree of overlap in habitat use and diet and differ in body size by a factor of 2–5×, eliciting particularly strong interspecific competition. In the Great Lakes region, fishers and martens occur both allopatrically and sympatrically; where they co‐occur, the numerically dominant species varies spatially. This natural variation in competitors and environmental conditions enables comparisons to understand how interference and exploitative competition alter dietary niche overlap and foraging strategies.We analysed stable isotopes (δ13C and δ15N) from 317 martens and 132 fishers, as well as dietary items (n = 629) from 20 different genera, to compare niche size and overlap. We then quantified individual diet specialization and modelled the response to environmental conditions that were hypothesized to influence individual foraging.Martens and fishers exhibited high overlap in both available and core isotopic δ‐space, but no overlap of core dietary proportions. When the competitor was absent or rare, both martens and fishers consumed more smaller‐bodied prey. Notably, the dominant fisher switched from being a specialist of larger to smaller prey in the absence of the subordinate marten. Environmental context also influenced dietary specialization: increasing land cover diversity and prey abundance reduced specialization in martens whereas vegetation productivity increased specialization for both martens and fishers.Despite an important dominance hierarchy, fishers adjusted their niche in the face of a subordinate, but superior, exploitative competitor. These findings highlight the underappreciated role of the subordinate competitor in shaping the dietary niche of a dominant competitor. [ABSTRACT FROM AUTHOR]

In order to reveal the status of habitat resource utilization and the degree of competition among lichens in Dabancheng mountainous areas. In this work, 30 plots were sampled in the field and the species cover data of the plots were investigated, and the niche characteristics and environmental factors of lichen community species were analyzed by using niche width, niche overlap index and ordination analysis in this Dabancheng mountainous area. The results were as follows:(1)The niche width of Rusavskia elegans and Circinaria contorta were the widest in Dabancheng mountainous area, indicating that they were more adaptable to different environments. The niche widths of other lichen species were narrow, indicating that the species used the environmental resources to a less extent.(2)The niche overlap value between species was generally low, with only a few species pairs having a high niche overlap value. The degree of niche differentiation between lichen species was high, indicating that the competition between species was not intense.(3)Although niche overlap was common among species with wider niche widths, niche overlap values were lower. However, some species with narrower niche widths had higher niche overlap values with other species. As a result, there was no clear linear relationship between niche overlap and niche width.(4)The distribution of lichen species varied along the altitudinal gradient, and altitude, light intensity, humidity, wind speed, and human disturbance were the dominant environmental factors for the different niche characteristics of lichen community species in the study area. In conclusion, as a result of habitat resource competition in Dabancheng mountainous area, lichen species occupied their own distinct niches, resulting in niche differentiation and relatively stable communities. The distribution of species differed significantly due to differences in habitat conditions along the altitudinal gradient. The results of this paper provides a theoretical basis for the study of lichen community assembly, which are of great significance to the conservation of lichen species diversity and habitat in the region. [ABSTRACT FROM AUTHOR]

Santolina is a clear example of a genus lying in an alpha‐taxonomic status, with species accepted only based on qualitative morphological descriptions. In particular, taxonomic issues still need to be resolved for Santolina populations from southern France and north‐eastern Spain, and so, we carried out an integrative taxonomic study involving morphometrics, cypsela morphometrics, niche overlap, and phylogenetic analysis based on six plastid markers (trnH‐psbA, trnL‐trnF, trnQ‐rps16, rps15‐ycf1, psbM‐trnD, and trnS‐trnG). Our results revealed that the current taxonomic circumscription is not adequate. In particular, the Santolina populations at the foothills of eastern Pyrenees, previously included in the variability of Santolina benthamiana, have to be considered as a distinct species, namely, Santolina intricata. In addition, despite their high phylogenetic relatedness, S. benthamiana s.str. and Santolina ericoides can still be considered as distinct species due to clear morphological and ecological differentiation. Finally, we demonstrated that three different subspecies can be recognized in Santolina decumbens, a species endemic to Provence. For one of these subspecies, due to its extremely restricted distribution range, conservation issues are pointed out. [ABSTRACT FROM AUTHOR]

The management of infectious wildlife diseases often involves tackling pathogens that infect multiple host species. Chronic wasting disease (CWD) is a prion disease that can infect most cervid species. CWD was detected in reindeer (Rangifer tarandus) in Norway in 2016. Sympatric populations of red deer (Cervus elaphus) and moose (Alces alces) are at immediate risk. However, the estimation of spillover risk across species and implementation of multispecies management policies are rarely addressed for wildlife. Here, we estimated the broad risk of CWD spillover from reindeer to red deer and moose by quantifying the probability of co‐occurrence based on both (1) population density and (2) habitat niche overlap from GPS data of all three species in Nordfjella, Norway. We describe the practical challenges faced when aiming to reduce the risk of spillover through a marked reduction in the population densities of moose and red deer using recreational hunters. This involves setting the population and harvest aims with uncertain information and how to achieve them. The niche overlap between reindeer and both moose and red deer was low overall but occurred seasonally. Migratory red deer had a moderate niche overlap with the CWD‐infected reindeer population during the calving period, whereas moose had a moderate niche overlap during both calving and winter. Incorporating both habitat overlap and the population densities of the respective species into the quantification of co‐occurrence allowed for more spatially targeted risk maps. An initial aim of a 50% reduction in abundance for the Nordfjella region was set, but only a moderate population decrease of less than 20% from 2016 to 2021 was achieved. Proactive management in the form of marked population reduction is invasive and unpopular when involving species of high societal value, and targeting efforts to zones with a high risk of spillover to limit adverse impacts and achieve wider societal acceptance is important. [ABSTRACT FROM AUTHOR]

The three-spined stickleback Gasterosteus aculeatus was introduced into Lake Constance in the 1940s and occupied a limited range until late 2012. Since then the species has expanded from a solely littoral habitat in Upper Lake Constance, but now makes seasonal migrations into the pelagic zone. This behavioral change has been accompanied by a drastic increase in stickleback abundance. In order to integrate information about feeding of sticklebacks in Upper Lake Constance over two consecutive years, stomach content analysis was combined with seasonal stable isotope analysis on two types of tissue (muscle and liver). Isotope values were also obtained for zooplankton, whitefish larvae and eggs. We calculated the contribution of potential food sources for sticklebacks' diet using a Bayesian mixing model (SIMMR). Furthermore, we determined stickleback trophic position, and d15N and d13C values were compared with those of other fish species of Lake Constance. The results of the Bayesian model as well as the stomach content analysis showed clear evidence of stickleback predation on fish eggs and larvae. Stickleback d15N values were elevated during winter and comparable to those of piscivorous pike, while d15N values of zooplankton were reduced, and those of whitefish larvae were similar to those of sticklebacks after accounting trophic fractionation of N isotopes. Trophic position calculations further identified sticklebacks as piscivorous, while the δ13C values of the liver and stomach content analysis suggests that a benthic-pelagic species pair may exist in Lake Constance. These findings support the hypotheses that sticklebacks in Lake Constance can display piscivorous feeding behaviour on sympatric fish species, most likely whitefish larvae and eggs. [ABSTRACT FROM AUTHOR]

Many pathogens can infect several host species, which complicates the management of wildlife diseases. Even for generalist pathogens, hosts are not equally competent, and variable niche overlap between hosts leads to different exposure levels within hosts when compared with that between hosts. Hence, the processes determining spillover risk and the subsequent transmission dynamics within and between species differ.Chronic wasting disease (CWD) is a contagious prion disease of the cervids detected across expanded geographic ranges over the last few decades. Multihost management has become topical with CWD detection among reindeer Rangifer tarandus in Europe, with an immediate spillover risk to sympatric species. Here, I argue for the use of a community epidemiological framework that distinguishes between‐ and within‐host dynamics arising from host competence and exposure processes.In CWD, host competence is mainly determined by how variants of the prion protein gene (PRNP) affect susceptibility. The exposure level is not only linked to the density of infected and susceptible hosts both within and between species but also to the spatiotemporal niche overlap between species and social organization within species.Mule deer Odocoileus hemionus and white‐tailed deer Odocoileus virginianus are highly susceptible and expected to show true multihost dynamics; however, mule deer have a higher CWD prevalence in sympatric areas, indicating only partially linked dynamics. Moose Alces alces are highly susceptible, but cases of CWD‐infected moose are few and appear to be spillover events with subsequent epidemic die outs. Elk Cervus canadensis have less susceptible PRNP variants and low levels of prion shedding in lymphoid tissues, indicating lower contagiousness. CWD prevalence in elk is lower and appears to result from spillover and subsequent within‐species emergence, which is partially independent of sympatric deer.Synthesis and applications. Stronger awareness of the different expected CWD dynamics within and between species may facilitate effective surveillance and management. Surveillance should consider the potential lack of linked dynamics between species when designing sampling. Multihost management can target niche overlap at different scales to limit spillover risk: (1) geographic distribution ranges, (2) density reductions in overlap zones and (3) co‐use of transmission hot spots. [ABSTRACT FROM AUTHOR]

Simple Summary: Two species belonging to the genus Pseudaulacaspis MacGillivray, 1921 (Hemiptera: Diaspididae), Pseudaulacaspis pentagona (Targioni Tozzetti, 1886) and Pseudaulacaspis prunicola (Maskell, 1895) are well-known pests for a great variety of ornamental plants and fruit trees worldwide. Both are notorious pests and significantly similar in morphology characteristics, life cycle, and ecological conditions, making it quite challenging to distinguish between the two species. In this paper, we implemented an integrative approach combining morphological, molecular, and ecological niche analyses in order to species delimitation. Overall, our findings indicate that the results further underpin the notion that the two species are closely related but distinct. We show that the integration of multiple approaches is useful in identifying morphologically similar species of the genus Pseudaulacaspis, overcoming the difficulties encountered when using traditional taxonomy alone. Pseudaucalaspis pentagona and P. prunicola are notorious pests and commonly feed on various ornamental plants and fruit trees worldwide. The two species share many host-plant species, and are similar in morphological characteristics and life cycle, making it difficult to distinguish to distinguish between them. In this study, morphological characteristics, molecular evidence, and ecological niches were used to define these species. We performed PCA analysis on 22 morphological characteristics that allowed the delineation of the species. We then sequenced the COI gene of both species revealing five populations of P. pentagona and one population of P. prunicola, and the higher support rate could distinguish the two species. We also identified the potential distribution area of the two species based on the MaxEnt niche model, which showed that the degree of niche overlap was high, but that they occupied different niches. Ultimately, we combined three lines of evidence to show that the two species are distinctly different. This study supports species definition using combined morphology, genetics, and ecology and provides a theoretical basis for the effective control of these two pests in the future. [ABSTRACT FROM AUTHOR]

The study is to explore the dynamics of community structure, diversity, interspecific relationships and stability during naturalized developmental vegetation restoration which realized by natural interaction between plantation and native trees without human's involvement. The naturalized developmental restored forests in Baxianshan National Reserve were divided into three typical stages (i.e. Pinus tabulaeformis forest stage, mixed forest stage and near-natural forest stage) according to the ratio of P. tabulaeformis coverage to arbor layer, and the zonal natural secondary forests for control. According to the data of each wood gauge, we focused on the dynamics of community in terms of structure, diversity and stability. We found that, (i) The composition of dominant populations kept stable since the mixed forests stage and the α -diversity increased with restoration; (ii) The diameter class structure of tree layer exhibited a tendency of bell-shaped type toward inverted J-type, indicating an active regenerating and developmental status; (iii) Niche width of dominant populations such as Juglans mandshurica , Quercus mongolica , Quercus variabilis and Tilia amurensis increased during restoration, while that of Quercus dentata population decreased after playing a pioneer role; (iv) The proportion of negative association and high niche overlapped population pairs (>0.5) both decreased with restoration. In summary, naturalized developmental restoration has promoted the actively developing and regenerating of populations and improved the healthy restoration of plantation community. The status and interrelationships of populations were still being adjusted. The results provide a reference for revealing the dynamic characteristics of vegetation community development in naturalized developmental restoration of plantations. [ABSTRACT FROM AUTHOR]

Phellodendron amurense is national second-class protected plant. The quantitative analysis on the niche characteristics of dominant tree populations in broad-leaved mixed forest of Phellodendron amurense can provide theoretical basis for the protection of Phellodendron amurense and maintaining species diversity. Based on the 9 th national forest inventory in Jilin Province, the Phellodendron amurense broad-leaved mixed forest community in Changbai Mountain was investigated and the methods of importance value, Levins niche width, Shannon-Wiener niche width and Pianka niche overlap were used to analyze the niche characteristics of dominant tree populations in this region. The results showed that, there were 25 broad-leaved species, accounting for 96. 15% of the total, and the important value of Phellodendron amurense in the broad-leaved mixed forest was the largest. The Levins and Shannon-Wiener niche width indices were basically the same in order. The species with the largest niche width was Phellodendron amurense, followed by Juglans mandshurica. The niche overlap value of species such as Phellodendron amurense with Butula costata, Juglans mandshurica and Ulmus laciniata was large. The niche width and niche overlap degree showed obvious consistency. However, the niche width and niche overlap of some species were opposite, such as Carpinus turczaninowii vs. Quercus dentata, Robinia pseudoacacia, and Tilia tuan, Phellodendron amurense vs. Pinus koraiensis, which was related to the ecological habits, habitat characteristics and spatial distribution of the tree species. [ABSTRACT FROM AUTHOR]

To enable long-term coexistence, species need to differentiate at least one of the three main dimensions of the ecological niche (temporal, spatial, or trophic dimension). Here, we investigated whether mammalian predators (Chrysocyon brachyurus, Cerdocyon thous, Lycalopex vetulus, and Puma concolor) follow the prediction of trophic niche partitioning, which is expected when partitioning of food resources represents an important mechanism for coexistence. We predicted low niche overlap in general and low between P. concolor and the other species. We analyzed 207 fecal samples collected at a landscape composed of forest remnants immersed in Eucalyptus plantations. Food items (animals and plants) were identified using exoskeletons, feathers, scales, teeth, hair, and seeds. We calculated the frequency and percentage of occurrence of food items, niche breadth, and niche overlap between pairs of species. Prey size was similar among all predators, consuming mainly small-sized prey (<1 kg). However, niche breadth was larger for smaller carnivores compared to larger ones. No species pair showed significantly lower niche overlap than expected by chance. Our study provided detailed information on trophic resource use of sympatric carnivores, showing that trophic niche partitioning seems not to be crucial for the coexistence of carnivores in the study area. [ABSTRACT FROM AUTHOR]

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Investigations into niche dynamics and interspecific interactions are crucial to assess the vulnerability of threatened species to competition and environmental change. The Whenua Hou Diving Petrel Pelecanoides whenuahouensis is a critically endangered seabird, specializing in breeding in sand dunes in Aotearoa (New Zealand). The species is at risk from competition for burrow sites with the abundant, habitat‐generalist Common Diving Petrel Pelecanoides urinatrix chathamensis, among other terrestrial and near‐shore threats (storm‐induced erosion and vessel‐based light pollution). However, Whenua Hou Diving Petrel foraging niches at sea and associated threats are poorly understood. We sampled blood and feathers from both species on Whenua Hou (Codfish Island) during 2017–19 and used stable isotope (δ15N and δ13C) analyses to quantify foraging niche dynamics and interspecific interactions. During incubation periods, when birds are restricted by central place foraging, diving petrels exhibited clear niche segregation. Whenua Hou Diving Petrels were more generalist feeders with wider isotopic niches than Common Diving Petrels, which exhibited restricted isotopic niches and fed in neritic waters. During non‐breeding periods, foraging niches expanded, and segregation was reduced, as both species dispersed into the Southern Ocean. These patterns were largely consistent among years, despite varying climatic conditions. However, Common Diving Petrel foraging niches appeared to shrink during El Niño conditions, suggesting environmental sensitivity. In contrast, the consistently stable, generalist foraging niches of Whenua Hou Diving Petrels suggested potential limited sensitivity to competition and impacts of environmental change at sea. Recovery efforts should, therefore, focus on addressing the previously identified terrestrial and near‐shore threats. [ABSTRACT FROM AUTHOR]

Mangroves are one of the most important wetland ecosystems. The development of fisheries in tropical and subtropical bays or estuaries is closely associated with mangroves since the high heterogeneity of the mangrove ecosystem provides a suitable habitat for marine organisms. However, multiple factors have led to a significant reduction in mangroves, such as water pollution, disease, insect pests, invasive alien species, and climate change. It is crucial to understand the relationships among organisms, as well as the interactions between organisms and their environment, by studying the ecological niche width and overlap of species. Therefore, two new perspectives of ecological niche width and ecological niche overlap were used to understand the interspecific ecological relationships, competition mechanisms, and resource utilization status of fish communities in mangrove forests. Based on the data collected during seasonal sampling in July 2019 (summer), October 2019 (autumn), January 2020 (winter), and May 2020 (spring) in the Nanliujiang Estuary, the index of relative importance (IRI), Shannon index, and Pianka index were employed to analyze the temporal and spatial niche of the main fish species in the mangrove creeks and to study niche differentiation among the main fish species by redundancy analysis. A total of 17,680 individual fish were collected in this study, belonging to 12 orders, 23 families, 37 genera, and 45 species. Ten main fish species with IRI>100 were identified. Among the main fish species, the temporal niche breadth ranged from 0.46 to 1.78, with the highest of which belonging to Butis butis (1.78) and the lowest belonging to Pseudogobius javanicus (0.46). The spatial niche breadth ranged from 0.81 to 2.05, with the highest of which belonging to Synechogobius ommaturus (2.05) and the lowest belonging to P. javanicus (0.81). The spatiotemporal niche breadth of six species was greater than 2 (wide-niche species) that included Mugil cephalus, Coptodon zillii, Bostrychus sinensis, S. ommaturus, B. butis, and Pisodonophis boro. With regard to overlap, the temporal niche overlap between M. cephalus and P. javanicus was the highest (0.928), whereas that between Ambassis urotaenia and Terapon jarbua (0.001) was the lowest. The spatial niche overlap between A. urotaenia and Gambusia affinis was the highest (0.979), whereas that between M. cephalus and P. javanicus (0.178) was the lowest. Finally, the spatiotemporal niche overlap between C. zillii and P. javanicus was the highest (0.822), whereas that between A. urotaenia and Terapon jarbua (0.001) was the lowest. The two-dimensional temporal and spatial niche pairs in the mangrove creeks of the Nanliujiang River Estuary significantly overlapped (Qik > 0.6), accounting for 6.7% of the total species pairs, indicating that the temporal and spatial distributions of species were quite different and the temporal and spatial niche overlap was affected by seasonal changes. Redundancy analysis revealed that the main factors affecting spatiotemporal niche differentiation of the main fish species in the mangrove creeks of the Nanliujiang Estuary were water temperature, salinity, and Chlorophyll a. And the main fish biomass in winter was positively correlated with salinity; the main fish biomass in spring was positively correlated with dissolved oxygen, pH and Chlorophyll a; the main fish biomass in summer was positively correlated with total organic carbon, water temperature and Chlorophyll a; the main fish biomass in autumn was positively correlated with total nitrogen, turbidity and total phosphorus.