Niche Overlap Of Species Research Articles

Mowing mitigates the negative impacts of long-term warming on community composition and niche characteristics of alpine meadow on the Tibetan Plateau

Climate warming and human disturbance are supposed to have significantly impacted the alpine grasslands. However, it is still unclear how human activity affects the community composition and niche characteristics in response to warming. We conducted a two-factorial experiment in an alpine meadow, and set up four treatments: warming, mowing, warming with mowing, and control. Based on the investigation of community composition and niche characteristics, we evaluated the impacts of soil carbon, nitrogen, and phosphorus on species niche overlap. The results showed that mowing significantly increased species richness of Grass, Sedge, Forbs and the importance value of Sedge compared to warming (P < 0.05). The niche breadth of species (>50%) was reduced by warming, but increased under mowing. The niche overlap mainly occurred between Grass and Forbs in warming, while it was evenly distributed among species after mowing, which alleviated the negative effects of warming on interspecific competitiveness. Warming increased the number of species pairs with a niche overlap value >0.9 by 24.15%, while warming with mowing decreased it by 2.7%. The number of species pairs with niche overlap was significantly correlated with soil total nitrogen and soil available nitrogen (P < 0.05). In particular, the species pairs with highly competitive showed a greater dependency on soil nitrogen. Our work highlights that moderate utilization and soil nitrogen are two crucial factors influencing the response of community structure in alpine meadows to future climate change. The study provides an important reference for predicting and addressing the impact of global climate change on adaptive management and grassland protection.

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 specialization and community niche space increase with species richness in filter‐feeder assemblages

AbstractEcological theory posits that higher species richness should be associated with greater exploitation of resources and niche packing resulting from either increasing species niche overlap or specialization of species' niches. Research evaluating niche theory in animals tends to focus on organisms among functional feeding guilds, while resource partitioning might be more critical within functional groups. Freshwater mussels (Family: Unionidae) are a diverse and imperiled group of animals that are ideal models to test niche occupancy due to their functional similarity as filter‐feeders and their occurrence in spatially and temporally stable multispecies aggregations. We evaluated the relationship between species richness and the trophic niche area for 25 mussel species occurring in 22 aggregations in the southeastern United States using stable isotope analysis (δ13C and δ15N) of soft tissue (n = 1057). Mean species standard ellipse area decreased with species richness, whereas ellipse overlap was not related to richness, indicating increased niche specialization may be the primary mechanism allowing coexistence in species‐rich communities. Total community isotopic area increased with richness, suggesting species‐rich communities also use a broader range of resources and may not be species‐saturated. Overall, our data support the niche‐packing hypothesis by illustrating the importance of niche partitioning within a species‐rich guild of aquatic animals.

Anthropogenic fire patterns affect niche breadth and niche overlap in sympatric songbird species

The severity of wildfires increases globally, and return intervals decrease. Fires can benefit biodiversity, as post-burn early successional stages provide diverse habitats and niches for many species. How fire disturbance affects niche use and niche overlap of species is poorly understood so far. We studied the effect of anthropogenic fire on breeding habitat use, niche breadth and niche overlap of five sympatric bunting species breeding in wetlands of the Amur River floodplain (Russian Far East). Fire frequency, measured as the time an area burnt in the period 2000 to 2017, was mapped from Landsat imagery and related to the presence or absence of the species. Niche breadth and niche overlap were calculated separately for occurrences in burned (within the study year) and unburned patches. Fire frequency characterized differences in niche use among the species, but the probability of presence was not affected by recent fire in four of five species. Niche breadth was significantly lower in recently burned patches, but we found no increase in niche overlap between species after fire. Instead, the studied species seemed to occupy similar patches before and after fire, possibly because of a high site fidelity. Our results clearly show that fire frequency is a major determinant for the niche separation in the five studied species, while recent fire does not affect niche overlap.

Foraging behaviour of sympatrically breeding macaroni (Eudyptes chrysolophus) and chinstrap (Pygoscelis antarcticus) penguins at Bouvetøya, Southern Ocean

Species with similar ecological requirements that overlap in range tend to segregate their niches to minimize competition for resources. However, the niche segregation possibilities for centrally foraging predators that breed on isolated Subantarctic islands may be reduced by spatial constraints and limitations in the availability of alternative prey. In this study we examined spatial and trophic aspects of the foraging niches of two sympatrically breeding penguin species, macaroni (Eudyptes chrysolophus; MAC) and chinstrap (Pygoscelis antarcticus; CHIN) penguins, at Bouvetøya over two breeding seasons. To measure at-sea movements and diving behaviour, 90 MACs and 49 CHINs were equipped with GPS loggers and dive recorders during two austral summer breeding seasons (2014/15 and 2017/18). In addition, blood samples from tracked birds were analysed for stable isotopes to obtain dietary information. CHINs displayed marked interannual variation in foraging behaviour, diving deeper, utilizing a larger foraging area and displaying enriched values of δ15N in 2014/15 compared to the 2017/18 breeding season. In contrast, MACs dove to similar depths and showed similar δ15N values, while consistently utilizing larger foraging areas compared to CHINs. We suggest that low krill abundances in the waters around Bouvetøya during the 2014/15 season resulted in CHINs shifting toward a diet that increased their niche overlap with MACs. Our findings may partly explain the decreasing number of breeding CHINs at the world’s most remote island, Bouvetøya, while also highlighting the importance of characterizing niche overlap of species using multi-season data sets.

Foraging guild structure and niche characteristics of wintering waterbirds at Lake Shengjin, lower reaches of the Yangtze River

集团结构和生态位特征是量化动物群落组织过程的重要指标，鸟类集团结构及其食物资源分割的分析对于理解群落中不同鸟种生态适应性具有重要意义.越冬水鸟集团结构和生态位特征取决于食物资源的丰富度和可获得性.本文通过对升金湖越冬水鸟的觅食生境和觅食行为的观察，对水鸟群落的集团结构进行划分，采用Levins指数和Pianka指数计算生态位宽度和生态位重叠度.结果表明，升金湖越冬水鸟可被划分为4个觅食集团，即G1浅水啄食集团、G2草滩啄食集团、G3广食性集团和G4深水潜水觅食集团.在浅水和中水区的觅食集团物种组成比深水区的水鸟集团丰富.G3广食性集团的生态位宽度远高于其余3个特化集团.比较而言，所有水鸟物种的觅食行为均较特化，但在觅食生境方面却较宽化.同一集团内物种间的生态位重叠远高于集团间的生态位重叠.G3广食性集团内物种的生态位重叠度低于其它特化集团内物种的生态位重叠度.研究结果表明，升金湖越冬水鸟群落集团结构主要受食物资源空间配置及其可利用性的影响.水鸟群落结构和生态位特征的信息对监测升金湖湿地的质量和制定有效的湿地保护策略都具有重要意义.;Guild structure and niche characteristics are important indicators to quantify the assemble process of animal community. It is of great significance to analysis bird guild structure and food resource partitioning for understanding ecological adaptability of different bird species in a community. The guild structure and niche characteristics of wintering waterbirds depend on the abundance and availability of food resources. In this study we divided the guild structure of waterbird community based on the data of foraging habitat and foraging behavior of wintering waterbirds collected at Lake Shengjin, and calculated the niche width and niche overlap using Levin's index and Pianka index. The results showed that the waterbirds at Lake Shengjin can be divided into four different foraging guilds, namely the G1, pickers in shallow-water, G2, pickers in grassland, G3, generalists and G4, divers. The species composition of foraging guilds in shallow and middle-depth water is richer than that in deep water. The niche width of G3 generalists is much higher than that of the other three specialized species guilds. In comparison, the foraging behavior of all waterbird species is more specialized, but the foraging habitat is more generalized. The niche intra-guild overlap of waterbird species is much higher than that of inter-guilds. The niche overlap of species in G3 generalist is lower than that in other specialized guilds. The results show that the guild structure of wintering waterbird community at Lake Shengjin mainly affected by the spatial allocation and availability of food resources. The information of water bird community structure and niche characteristics is of great significance for monitoring the quality of Lake Shengjin wetland and developing effective wetland protection strategies.

How do similar community dynamics yield different population dynamics and spatial distributions of species?

The distribution of biotic and abiotic factors creates ecological niches. Despite the link between both the biotic and abiotic components of a species niche and its geographic distribution, most approaches to species-distribution modeling correlate the occurrence of a single species with broad-scale environmental variables, but do not include biotic interactions. We studied the relative effects of biotic and abiotic factors on community composition and dynamics in a man-made ecosystem (i.e., a grain-storage system). We studied the population dynamics of 10 insect species at two climatically distinct study sites: a site with a Mediterranean climate and a site with a semi-arid climate. All species were found to aggregate at both sites and similar community dynamics were observed at the two sites. However, there were differences in the relative importance of biotic and abiotic factors in the formation of communities in the two habitats. This difference yielded different population dynamics and spatial distributions. The Mediterranean site was characterized by species niche overlap and communities at that site were less dense. In contrast, in the semi-arid habitat, species tended to have distinct spatial distribution and there was a high level of community density. These results can be viewed as examples of within- and between-patch coexistence. We discuss the possibility that there may be gradual shifts in the relative importance of within- and between-patch coexistence. Small continuous changes, such as global climate change, could induce such shifts, leading to similar temporal and spatial patterns in the current Mediterranean climate.

Trophic niches determined from fatty acid profiles of sympatric coral reef mesopredators

Previous research has identified similar trophic levels in a wide range of coral reef sharks and large teleost fishes but has been unable to resolve the extent of dietary overlap and resource sharing that lead to interpretation of functional roles and, hence, adequately describe interaction strengths in food webs. We used fatty acid (FA) profiles of muscle and plasma reflecting the diet of several mesopredators to better understand the trophic structure and functioning of Great Barrier Reef ecosystems. Multivariate analysis identified significant dietary overlap between 2 shark species (whitetip reef shark Triaenodon obesus and grey reef shark Carcharhinus amblyrhynchos), but whitetip reef sharks occupied a smaller niche area than grey reef sharks. We also found clear niche separation between sharks and teleost fishes (red throat emperor, coral trout, and grass emperor). All mesopredators sampled had high proportions of polyunsaturated FAs linking them to carnivory, but differences among species in trophic biomarker ratios suggest distinctive dietary sources. However, based on a degree of niche overlap of species sharing common diet, reef-dwelling teleost fishes such as coral trout also derive nutrients from pelagic environments. A faster analytical method to determine FA profiles, proven highly useful in tuna, was tested and deemed viable for muscle tissue of tropical teleost fishes and sharks, while questions remain for use of FA extraction of plasma in ecological studies. These results demonstrate that fine-scale inter-specific differences in diet exist between mesopredators in coral reef ecosystems. Our results raise important questions about the ecological influences of these species and energy flow among mesopredators in coral reef ecosystems.

When invasion may not be harmful: niche relations in a lizard assemblage

Some studies have suggested that non-native species invasions may threaten local diversity by creating homogenized environments. However, many studies have been based on limited or anecdotal data, and/or have failed to consider the influence of habitat modification together with possible influences of non-native species on native ones. Hemidactylus mabouia (Squamata, Gekkonidae) likely invaded natural environments in Brazil hundreds of years ago. Yet, little is known about whether it affects native lizard fauna. We tested whether H. mabouia negatively influences native lizard species richness and abundance on a regional scale and locally through niche overlap. We analyzed species abundance and richness of nine lizard assemblages, in five of which H. mabouia occurred. We evaluated niche overlap of species in a lizard assemblage with high H. mabouia abundance through null models. Niche axes included spatial use, temporal activity and diet. Although species abundance did not differ among sites with and without the invasive species, the presence of H. mabouia seems constrained to the richer assemblages sampled. We observed significantly higher niche overlap in spatial (ɸobs = 0.63; ɸexp = 0.37; Pobs ≥ Pexp = 0.0002) and trophic axes (ɸobs = 0.46; ɸexp = 0.17; Pobs ≥ Pexp < 0.001), but not in activity. When we considered all axes (three-dimensional niche), there was no overlapping among the lizard species. Our findings did not support the hypothesis that this non-native species negatively influences other sympatric lizard species.

Individual diet variation in a marine fish assemblage: Optimal Foraging Theory, Niche Variation Hypothesis and functional identity

Individual diet variation (i.e. diet variation among individuals) impacts intra- and inter-specific interactions. Investigating its sources and relationship with species trophic niche organization is important for understanding community structure and dynamics. Individual diet variation may increase with intra-specific phenotypic (or “individual state”) variation and habitat variability, according to Optimal Foraging Theory (OFT), and with species trophic niche width, according to the Niche Variation Hypothesis (NVH). OFT proposes “proximate sources” of individual diet variation such as variations in habitat or size whereas NVH relies on “ultimate sources” related to the competitive balance between intra- and inter-specific competitions. The latter implies as a corollary that species trophic niche overlap, taken as inter-specific competition measure, decreases as species niche width and individual niche variation increase. We tested the complementary predictions of OFT and NVH in a marine fish assemblage using stomach content data and associated trophic niche metrics. The NVH predictions were tested between species of the assemblage and decomposed into a between- and a within-functional group component to assess the potential influence of species' ecological function. For most species, individual diet variation and niche overlap were consistently larger than expected. Individual diet variation increased with intra-specific variability in individual state and habitat, as expected from OFT. It also increased with species niche width but in compliance with the null expectation, thus not supporting the NVH. In contrast, species niche overlap increased significantly less than null expectation with both species niche width and individual diet variation, supporting NVH corollary. The between- and within-functional group components of the NVH relationships were consistent with those between species at the assemblage level. Changing the number of prey categories used to describe diet (from 16 to 41) did not change the results qualitatively. These results suggest that, besides proximate sources, intra-specific competition favors higher individual diet variation than expected while inter-specific competition limits the increase of individual diet variation and of species niche overlap with species niche expansion. This reveals partial trophic resource partitioning between species. Various niche metrics used in combination allow inferring competition effects on trophic niches' organization within communities.

The role of niche overlap, environmental heterogeneity, landscape roughness and productivity in shaping species abundance distributions along the Amazon–Andes gradient

AbstractAimStatistical and ecological mechanisms shape species abundance distributions (SADs). A lack of correlation between ecological gradients and SAD shape would suggest that SADs are caused by purely statistical reasons. We evaluated the variation in the shape of SADs for communities in landscapes of differing variable connectivity, environmental heterogeneity, species niches overlap and productivity.LocationRainforests in the Madidi region (Bolivia).MethodsWe compiled biological and environmental information on 65 sites (a site being a group of two to six 0.1‐ha plots where woody plants of a diameter at breast height ≥ 2.5 cm were inventoried). We built unveiled (complete) SADs for each site and fitted Gambin models to those SADs. The Gambin α parameter served as a metric of SAD shape. Low α values characterize logseries‐like SADs, while high α values characterize lognormal‐like SADs. For each site, we estimated landscape roughness, environmental heterogeneity, species niche overlap and productivity. These variables were related to SAD shape by means of variation partitioning.ResultsSADs changed from logseries‐like to lognormal‐like along the elevational gradient. Many of our predictor variables were correlated: 40.4% of the variation in SAD shape could not be attributed to specific factors. However, 50.62% of the variation in the SAD shape could be assigned to individual predictor matrices: 28.4% was explained exclusively by niche overlap, 15.41% exclusively by environmental heterogeneity, 5.20% exclusively by landscape roughness and 1.6% exclusively by productivity.Main conclusionsEcological processes related to the topographical/environmental complexities that vary across the elevational gradient are correlated with the SAD shape. Purely statistical mechanisms are apparently not sufficient to explain the changes in SAD shape. The most important factor is the mean overlap of the niches of the species of an assemblage: avoiding competition with co‐occurring species could be the most important mechanism driving species relative success at the ≤100 km2 scale.

Niche partitioning in tenebrionid species (Coleoptera: Tenebrionidae) inhabiting Mediterranean coastal dunes

We analyzed the abundance, distribution and niche overlap of species (Pianka's Ojk index) in tenebrionid beetle communities inhabiting different biotopes in Tyrrhenian and Adriatic sand dunes. The rank abundance distribution of the different species has the form of a geometric series in both communities as predicted by the niche preemption hypothesis for communities in harsh environments. Mean niche overlap values did not deviate significantly from null expectations, which indicates random interspecific interactions. These results, coupled with evidence of species habitat preferences, led us to conclude that the community organization of tenebrionid species inhabiting coastal dunes is determined more by habitat preferences than interspecific competition.

Complex relationships between species niches and environmental heterogeneity affect species co-occurrence patterns in modelled and real communities.

Species co-occurrence analysis is commonly used to assess how interspecific interactions dictate community assembly. Non-random co-occurrences, however, may also emerge from niche differences as well as environmental heterogeneity. The relationships between species co-occurrence patterns, environmental heterogeneity and species niches are not fully understood, due to complex interactions among them. To analyse the relationships among these patterns and processes, I developed synthetic community models and analysed a large dataset of tree species across the conterminous United States. Niche overlap and environmental heterogeneity had significant and contrasting effects on species co-occurrence patterns, in both modelled and real communities. Niche breadth, in turn, affected the effect sizes of both variables on species co-occurrence patterns. The effect of niche breadth on the relationship between co-occurrence and niche overlap was markedly consistent between modelled and real communities, while its effect on the relationship between co-occurrence and environmental heterogeneity was mostly consistent between real and modelled data. The results of this analysis highlight the complex and interactive effects of species niche overlap, niche breadth and environmental heterogeneity on species co-occurrence patterns. Therefore, inferring ecological processes from co-occurrence patterns without accounting for these fundamental characteristics of species and environments may lead to biased conclusions.

NICHE OVERLAP OF SPHENISCIDAE ON ELEPHANT ISLAND, ANTARCTICA

Stomach content samples were collected from Gentoo Penguin and Chinstrap Penguin in order to analyze the diet and the niche overlap on Elephant Island, Antarctica. A total of 56 Gentoo Penguin samples and 71 Chinstrap Penguin samples were collected, during the two austral breeding seasons, 2010/11 and 2011/12, on the Stinker Point region. E. superba was the most abundant prey, (69% FO and 98% FO) for Gentoo and Chinstrap Penguin, respectively. Nine species of fish and one species of cephalopod, were identified by specific level. We observed a niche overlap of species, by the use of the same food resources, since these species occurs sympatrically in the same region. This study also demonstrated that the specific variation of trophic niches occupied by the species may be defined by the foraging behavior and by the selection of the food resources.

Ecological niche and species traits: key drivers of regional plant invader assemblages

Linking species traits to niche properties is fundamental to understand the spatial structure of invasive species assemblages and the invasion process itself. Using information on 74 invasive species in Spain, the aims of this paper are to (1) test whether invasive plant species assemblages follow a nested pattern at the regional scale, (2) inspect the relationship between range size and niche properties (position and breadth) of invasive species to test whether the nested pattern is a product of species niche overlap; and finally (3) examine how species traits of invaders are related to their niche properties. We show that regional invasive plant species assemblages in Spain are organized in nested subsets. Invasive species with restricted range occur in areas invaded by widespread invaders. By relating nestedness metrics to species' niche properties from multivariate analyses, we found that these restricted invaders are less tolerant of broad climatic and landscape conditions than widespread invaders. Finally, regarding the association between niche properties and species traits, we found that species with large environmental niche breadth commonly exhibit non N-fixing strategy, short-life span, and clonal growth, while those with niche position in anthropogenic coastal areas were perennial and clonal species of unintentional and agricultural origin. Using an integrative approach linking the regional spatial structure of invasive plant assemblages, species niche properties and species traits, we were able to under- stand the potential causes of invasive species distribu- tion in Spain. The approach developed in this research could be easily applied to other areas to disentangle the mechanisms driving invasive species distributions.

Using functional traits and phylogenetic trees to examine the assembly of tropical tree communities

Summary1. Niche theory proposes that species differences underlie both coexistence within communities and the differentiation in species composition among communities via limiting similarity and environmental filtering. However, it has been difficult to extend niche theory to species‐rich communities because of the empirical challenge of quantifying niches for many species. This has motivated the development of functional and phylogeny‐based approaches in community ecology, which represent two different means of approximating niche attributes.2. Here, we assess the utility of plant functional traits and phylogenetic relationships in predicting community assembly processes using the largest trait and phylogenetic data base to date for any set of species‐rich communities.3. We measured 17 functional traits for all 4672 individuals of 668 tree species co‐occurring in nine tropical rain forest plots in French Guiana. Trait variation was summarized into two ordination axes that reflect species niche overlap.4. We also generated a dated molecular phylogenetic tree based on DNA sequencing of two plastid loci (rbcLandmatK) comprising 97% of the individuals and 91% of the species in the plots.5. We found that, on average, co‐occurring species had greater functional and, to a lesser extent, phylogenetic similarity than expected by chance.6. We also found that functional traits and their ordination loadings showed significant, albeit weak, phylogenetic signal, suggesting that phylogenetic distance provides pertinent information on niche overlap in tropical tree communities.7. Synthesis. We provide the most comprehensive examination to date of the relative importance of environmental filtering and limiting similarity in structuring tropical tree communities. Our results confirm that environmental filtering is the overriding influence on community assembly in these species‐rich systems.

Elevated CO2 differentially alters the responses of coocurring birch and maple seedlings to a moisture gradient.

To determine the effects of elevated CO2 and soil moisture status on growth and niche characteristics of birch and maple seedlings, gray birch (Betula populifolia) and red maple (Acer rubrum) were experimentally raised along a soil moisture gradient ranging from extreme drought to flooded conditions at both ambient and elevated atmospheric CO2 levels. The magnitude of growth enhancement due to CO2 was largely contingent on soil moisture conditions, but differently so for maple than for birch seedlings. Red maple showed greatest CO2 enhancements under moderately moist soil conditions, whereas gray birch showed greatest enhancements under moderately dry soil conditions. Additionally, CO2 had a relatively greater ameliorating effect in flooded conditions for red maple than for gray birch, whereas the reverse pattern was true for these species under extreme drought conditions. For both species, elevated CO2 resulted in a reduction in niche breadths on the moisture gradient; 5% for gray birch and 23% for red maple. Species niche overlap (proportional overall) was also lower at elevated CO2 (0.98 to: 0.88: 11%). This study highlights the utility of of experiments crossing CO2 levels with gradients of other resources as effective tools for elucidating the potential consequences of elevated CO2 on species distributions and potential interactions in natural communities.

Components of Diversity: Multivariate Analysis with Interaction

We use the effective number of species as a measure of diversity of a community. Shannon's function H' and other logarithmic or multiplicative indices of diversity give components of diversity which are difficult to interpret. Exp(H') and the reciprocal of Simpson's index, which measure the effective number of species, and linearly related to the number of species. The effective number of species is partitionable into components determined by resource dimension and their interaction. Components of diversity measure differences which are found by using various niche axes alone and together. Our method allows the analysis of the relations between the overall structure of the community or guilds and their resource space. The residual component of diversity measures the niche overlap of species in respect to the resource dimensions studied.