Spatial Niche Overlap Research Articles

Leopards at large: population density, habitat utilisation and spatio-temporal overlap of leopards (Panthera pardus) with competitors and prey in the Rajaji Tiger Reserve, northern India

Context In the vicinity of the western Rajaji Tiger Reserve, a significant rise in conflicts between humans and leopards has occurred. These conflicts have resulted in a substantial number of human deaths, with 60% attacks resulting in deaths over a 4-year period. Aims This study aims to examine any potential connection among the non-breeding tigers, leopards, prey, humans and the increased occurrence of conflicts. Methods To address this objective, we conducted an analysis to evaluate the density of leopards, as well as their spatial and temporal behaviour with respect to tigers, prey and humans through on-site habitat use, circular statistics, diel-overlap as well spatial niche breadth and spatial-niche overlap. Key results Our findings showed one of the highest leopard-density estimates (excluding cubs) (mean ± s.e.) of 23.7 ± 4.8 per 100 km2. When examining on-site habitat use by leopards, we found three variables that had a negative influence, namely, human presence, slope, and the presence of tigers. The presence of a large prey (sambar) had a positive influence. Leopards, exhibiting the highest spatial-niche breadth, demonstrated a small overlap with both tigers and humans, while displaying a significant diel overlap with sambar. The niche overlap was notably high with sambar, but very low with humans and tigers. Conclusions Although tigers locally created a zone of spatial and temporal avoidance, at the population level the leopards experienced a surge in numbers in response to the reduced tiger numbers, indicated by their high density. This could be a cause of high leopard movement into nearby human settlements. This unique scenario could have contributed to conflict. Implications Understanding the coexistence among different species and the impact of transient animals is crucial to develop effective management strategies to mitigate conflict. This approach would facilitate and ensure the long-term survival of diverse large carnivores in the tropical forests of southern Asia through sustained support for conservation from local communities.

Spatiotemporal Mechanisms of the Coexistence of Reintroduced Scimitar-Horned Oryx and Native Dorcas Gazelle in Sidi Toui National Park, Tunisia.

Examining the distribution patterns and spatiotemporal niche overlap of sympatric species is crucial for understanding core concepts in community ecology and for the effective management of multi-species habitats within shared landscapes. Using data from 26 camera-traps, recorded over two years (December 2020-November 2022), in Sidi Toui National Park (STNP), Tunisia, we investigate habitat use and activity patterns of the scimitar-horned oryx (n = 1865 captures) and dorcas gazelle (n = 1208 captures). Using information theory and multi-model inference methods, along with the Pianka index, we evaluated the habitat characteristics influencing species distribution and their spatial niche overlap. To delineate daily activity patterns, we applied kernel density estimation. Our findings indicate minimal spatial overlap and distinct environmental factors determining suitable habitats for each species. Furthermore, we found significant temporal niche overlaps, indicative of synchrony in daily activity patterns, with both species showing peak activity at dawn and dusk. Our results indicated that oryx and gazelle differ in at least one dimension of their ecological niche at the current density levels, which contributes to their long-term and stable coexistence in STNP.

The Spatial Niche and Influencing Factors of Desert Rodents.

Resource partitioning may allow species coexistence. Sand dunes in the typical steppe of Alxa Desert Inner Mongolia, China, consisting of desert, shrub, and grass habitats, provide an appropriate system for studies of spatial niche partitioning among small mammals. In this study, the spatial niche characteristics of four rodents, Orientallactaga sibirica, Meriones meridianus, Dipus sagitta, and Phodopus roborovskii, and their responses to environmental changes in the Alxa Desert were studied from 2017 to 2021. Using the capture-mark-recapture method, we tested if desert rodents with different biological characteristics and life history strategies under heterogeneous environmental conditions allocate resources in spatial niches to achieve sympatric coexistence. We investigated the influence of environmental factors on the spatial niche breadth of rodents using random forest and redundancy analyses. We observed that the spatial niche overlap between O. sibirica and other rodents is extremely low (overlap index ≤ 0.14). P. roborovskii had the smallest spatial niche breadth. Spatial niche overlap was observed in two distinct species pairs, M. meridianus and D. sagitta, and P. roborovskii and D. sagitta. The Pielou evenness index of rodent communities is closely related to the spatial distribution of rodents, and the concealment of habitats is a key factor affecting the spatial occupation of rodents.

Spatial and temporal niche overlap of aardwolves and aardvarks in Serengeti National Park, Tanzania.

Species interactions can influence species distributions, but mechanisms mitigating competition or facilitating positive interactions between ecologically similar species are often poorly understood. Aardwolves (Proteles cristata) and aardvarks (Orycteropus afer) are nocturnal, insectivorous mammals that co-occur in eastern and southern Africa, and knowledge of these species is largely limited to their nutritional biology. We used aardwolf and aardvark detections from 105 remote cameras during 2016-2018 to assess their spatial and temporal niche overlap in the grasslands of Serengeti National Park, Tanzania. Using a multispecies occupancy model, we identified a positive interaction between occupancy probabilities for aardwolves and aardvarks. Slope, proportion of grassland and termite mound density did not affect the occupancy probabilities of either species. The probability of aardwolf, but not aardvark, occupancy increased with distance to permanent water sources, which may relate to predation risk avoidance. Diel activity overlap between aardwolves and aardvarks was high during wet and dry seasons, with both species being largely nocturnal. Aardwolves and aardvarks have an important ecological role as termite consumers, and aardvarks are suggested to be ecosystem engineers. Our results contribute to a better understanding of the spatial and temporal niche of insectivores like aardwolves and aardvarks, suggesting high spatial and temporal niche overlap in which commensalism occurs, whereby aardwolves benefit from aardvark presence through increased food accessibility.

Factors shaping a lizard community structure in a semiarid region of north-eastern Brazil

We assessed the roles of historical and recent factors on the structure of a Neotropical lizard community from Serra da Capivara, in the semiarid Caatinga of north-eastern Brazil. We found no phylogenetic structure in community composition. Spatial niche overlap was high for most species pairwise comparisons. Null model analyses indicated that mean spatial and trophic niche overlaps did not differ, while mean morphological niche overlap was significantly lower than expected by chance, indicating a community structured along the morphological niche axis but not along the trophic nor spatial niche axes. We suggest that the lack of spatial niche segregation and species association may be related to current environmental conditions, such as habitat homogeneity and climatic variables. Morphological and dietary niches were influenced by historical factors, with phylogeny accounting for most of the variation in our data. Most of the variation is accounted for by the divergence of basal lineages (Gekkota/Scincomorpha/Iguania). These segregations influence behaviour and foraging modes of the given clades. Finally, these results are quite like those found for lizard communities in Seasonal Tropical Dry Forests (STDFs) and Cerrado savannahs, which can be a starting point to discuss the relationship between these formations to Caatinga domain.

Food Habit, Spatial, and Dietary Niche Overlap of Three Sympatric Insectivorous Bats (Chiroptera) in the West Region of Cameroon

Food Habit, Spatial, and Dietary Niche Overlap of Three Sympatric Insectivorous Bats (Chiroptera) in the West Region of Cameroon

Anthropogenically driven spatial niche partitioning in a large herbivore assemblage

Understanding how human activity can influence species distributions and spatial niche partitioning between sympatric species is a key area of contemporary ecology. Extirpations of large mammalian populations, the result of a 15-year civil war, within the Gorongosa National Park in Mozambique, have been followed by an extended period of restoration. The species-specific recovery of these populations has provided an ideal system to identify how niche partitioning between coexisting species is altered as a consequence of extreme disturbance events. Here, we aimed to understand how distribution patterns of grazing herbivores, as well as spatial niche overlap between them, changed between the pre- and post-war scenarios. We focused on the following four grazer species: buffalo (Syncerus caffer); sable (Hippotragus niger); waterbuck (Kobus ellipsiprymnus); and zebra (Equus quagga). Using long-term aerial survey data, we quantified range size for each species, as well as spatial niche overlap between each species pair, for pre- and post-war periods. Range size of buffalo and zebra decreased drastically from the pre-war period; with both species inhabiting subsets of their historical distribution in the park. Sable and waterbuck have both colonised historically avoided habitat, with waterbuck doubling their pre-war range size. Spatial overlap between all four grazers pre-war was significantly high, indicating niche similarity; however, this decreased in the post-war period, with some species pairs displaying spatial niche dissimilarity. Our findings highlight how population responses to anthropogenic disturbance can result in significant alterations to species’ distributions, with consequences for patterns of niche similarity.

Niche Analysis of the Main Fish in the Lhasa River Basin

The Lhasa River is one of the five tributaries of the Yarlung Zangbo River. It is the main industrial, agricultural and animal husbandry area in Tibet. It plays an important ecological security barrier role in regulating regional climate and maintaining biodiversity. In order to understand the resource utilization ability and relationship of fish in Lhasa River, and provide basic data for the protection and sustainable utilization of fish diversity in Lhasa River, the fishery resources in September 2019 (autumn), June 2020 (summer), November 2020 (winter) and March 2021 (spring) were investigated for the first time. The main fish in the catch were determined by the Index of Relative Importance (IRI). Shannon index and Pianka’s index were used to analyze the niche breadth and overlap values of the main fish caught in Lhasa River Basin from three dimensions of time, space and space–time. The results show that a total of 1399 fish of 3 orders and 4 families were collected. Among them, there is one dominant species, Schizopygopsis younghusbandi, and five common species, Schizothorax waltoni, Schizothorax oconnori, Ptychobarbus dipogon, Triplophysa stenura and Carassius auratus. The spatial–temporal niche breadth ranges from 1.395 to 3.628. They are Schizopygopsis younghusbandi, Carassius auratus, Ptychobarbus dipogon, Schizothorax oconnori, Triplophysa stenura and Schizothorax waltoni in a declining order. The temporal niche breadth is generally small, indicating that the survival activities of the main fish are greatly affected by seasonal changes. The fluctuation range of spatial–temporal overlap value is 0–0.535, and only 20% of the total logarithm is meaningful. The species pairs with temporal niche overlap values exceeding 0.300 reached 80%, while the spatial niche overlap value is generally low. The results show that the spatial and temporal distributions of the main fish in Lhasa River were quite different, and the spatial and temporal niche overlap value of the relationship between species is obviously affected by the change in spatial distribution. This demonstrates that the competition relationship and intensity of the main fish are quite different in different spatial positions.

Niche partitioning by sympatric civets in the Himalayan foothills of Pakistan.

Niche overlap between sympatric species can indicate the extent of interspecific competition. Sympatric competing species can exhibit spatial, temporal, and dietary adjustments to reduce competition. We investigated spatial, temporal, and dietary niche overlap of sympatric Asian palm civet (Paradoxurus hermaphroditus) and small Indian civet ( Viverricula indica), in and around Pir Lasura National Park, Pakistan. We used remote cameras to determine the frequency and timing of detections to estimate spatial and temporal overlap, and prey remains from scats to estimate dietary overlap. We collected scat samples of Asian palm civet (n = 108) and small Indian civet (n = 44) for dietary analysis. We found low spatial (Oij = 0.32) and temporal (Δ = 0.39) overlap, but high dietary niche overlap (0.9) between these two civet species. Both civet species were detected at only 11 camera sites and small Indian civets were detected most frequently during 2:00-5:00 h and 8:00-10:00 h, whereas Asian palm civets detections were greatest during 20:00-2:00 h. The overall niche breadth of Asian palm civet was slightly narrower (L = 9.69, Lst = 0.31) than that of the small Indian civet (L = 10, Lst = 0.52). We identified 27 dietary items (15 plant, 12 animal) from scats of Asian palm civet including Himalayan pear (Pyrus pashia; 27%), Indian gerbil (Tatera indica; 10%), Rhesus monkey (Macaca mulatta; 4%), and insects (5%). Scat analysis of small Indian civets revealed 17 prey items (eight plant, nine animal) including Himalayan pear (24%), domestic poultry (15%), Indian gerbil (11%), and house mouse (Mus musculus; 5%). Both civet species consumed fruits of cultivated orchard species. Spatial and temporal partitioning of landscapes containing diverse foods appears to facilitate coexistence between Asian palm civets and small Indian civets.

Acoustic partitioning explains the coexistence between two Physalaemus species (Anura, Leptodactylidae) in the Atlantic Forest in Eastern Bahia State, Brazil

In this study we investigate the niche interaction between the frogs Physalameus cuvieri and Physalaemus kroyeri that occur in syntopy in water bodies of the Atlantic Forest located in the eastern Bahia State, Brazil. We investigated the niche width and overlap in the calling activity time, microhabitat use, diet composition, advertisement call, and body size. Both species preferred the same substrate and calling substrate categories, and showed low niche width values and high spatial niche overlap values. The pseudocommunity analysis revealed the absence of competition in space use. Ants and termites were the most important items in the diet of both species with the pseudocommunity analysis indicating an absence of competition in the diet. The two species demonstrate a greater similarity in body proportions and a high overlap in the calling activity time. However, they showed divergence in acoustic parameters, especially in the dominant frequency and call duration. Our results reinforce the role of advertisement call as a relevant attribute for anuran coexistence and highlight the importance of analyzing the various axes of the multidimensional niche for the most reliable description of the existence and magnitude of niche partitioning.

Determinants of resource use in lizard assemblages from the semiarid Caatinga, Brazil

AbstractNonsessile animals could partition the use of resources in different axes, reducing the effects of competition and allowing coexistence. Here, we investigated the spatial and trophic niche dimensions in four lizard assemblages in the Neotropical semiarid Caatinga to investigate the determinants of resource use and the extent to which lizards partition their niches. We sampled each lizard assemblage once, for 10 days, in the dry season of 2017 and 2018. In two lizard assemblages, we detected nonrandom niche overlap patterns that were higher or lower than expected by chance. The high niche overlap patterns suggest that either there is intense current competition for available microhabitats or an abundance of microhabitats. The lower niche overlap may be influenced by the presence of species adapted to sandy habitats (psammophilous), suggesting that spatial partitioning detected has historical basis, which is supported by the pPCA results and by the lack of patterns in the realized niche distribution of species across niche space. We detected trophic niche partitioning in three lizard assemblages. In one assemblage, we discovered random spatial and trophic niche overlap patterns, revealing that competition is not a determining factor in the structure of that assemblage. In fact, phylogenetic effects were predominantly the main determinants of resource use in the four studied lizard assemblages. Arid and semiarid habitats cover about one third of land surface of the world. Comparisons between our findings and those from other regions of the world may aid identify general trends in the lizard ecology of dry environments.

The Native Hymenoscyphus albidus and the Invasive Hymenoscyphus fraxineus Are Similar in Their Necrotrophic Growth Phase in Ash Leaves.

The populations of European ash and its harmless fungal associate Hymenoscyphus albidus are in decline owing to ash dieback caused by the invasive Hymenoscyphus fraxineus, a fungus that in its native range in Asia is a harmless leaf endophyte of local ash species. To clarify the behavior of H. albidus and its spatial and temporal niche overlap with the invasive relative, we used light microscopy, fungal species-specific qPCR assays, and PacBio long-read amplicon sequencing of the ITS1-5.8S-ITS2 region to examine fungal growth and species composition in attached leaves of European ash. The plant material was collected from a healthy stand in central Norway, where ash saplings in late autumn showed leaflet vein necrosis like that commonly related to H. fraxineus. For reference, leaflet samples were analyzed from stands with epidemic level of ash dieback in southeastern Norway and Estonia. While H. albidus was predominant in the necrotic veins in the healthy stand, H. fraxineus was predominant in the diseased stands. Otherwise, endophytes with pathogenic potential in the genera Venturia (anamorph Fusicladium), Mycosphaerella (anamorph Ramularia), and Phoma, and basidiomycetous yeasts formed the core leaflet mycobiome both in the healthy and diseased stands. In necrotic leaf areas with high levels of either H. albidus or H. fraxineus DNA, one common feature was the high colonization of sclerenchyma and phloem, a region from which the ascomata of both species arise. Our data suggest that H. albidus can induce necrosis in ash leaves, but that owing to low infection pressure, this first takes place in tissues weakened by autumn senescence, 1–2 months later in the season than what is characteristic of H. fraxineus at an epidemic phase of ash dieback. The most striking difference between these fungi would appear to be the high fecundity of H. fraxineus. The adaptation to a host that is phylogenetically closely related to European ash, a tree species with high occurrence frequency in Europe, and the presence of environmental conditions favorable to H. fraxineus life cycle completion in most years may enable the build-up of high infection pressure and challenge of leaf defense prior to autumn senescence.

Predicting the distribution of Australian frogs and their overlap with Batrachochytrium dendrobatidis under climate change

AbstractAimAmphibians, with over 40% of assessed species listed as threatened, are disproportionately at risk in the global extinction crisis. Among the many factors implicated in the ongoing loss of amphibian biodiversity are climate change and the disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd). These threats are of particular concern in Australia, where Bd has been implicated in the declines of at least 43 frog species, and climate change is emerging as an additional threat. We explore how climate change is likely to affect the distributions of Australian frog species and Bd to the year 2100, and how the spatial and climatic niche overlap between chytridiomycosis‐declined frogs and Bd could shift.LocationAustralia.MethodsWe used species distribution modelling to infer the current and future distribution of 141 Australian frog species and Bd, under two emissions scenarios. We used various metrics of niche similarity to quantify predicted alterations to spatial interactions between Bd and frog species.ResultsClimate change is likely to have a variable impact on frog distributions in Australia, with some 23 and 47 species, primarily in southern Australia, predicted to lose at least 30% of their current distributions under low and high emissions scenarios, respectively. In contrast, 69 and 68 species, respectively, have potential to increase their distributions, primarily in northern Australia. While the distribution of Bd is predicted to decrease, the proportional spatial and niche overlap between Bd and susceptible frog species is predicted to remain little changed, and in some cases, to increase.Main conclusionsAlthough effects will be variable across the continent, climate change is likely to be a threatening factor to many Australian frog species. Additionally, chytridiomycosis is likely to remain a significant threat to many frog species, as any reductions to the pathogen's distribution largely coincide with geographic range contractions of chytridiomycosis‐susceptible species.

Intra-guild spatial niche overlap among three small falcon species in an area of recent sympatry

Climate warming and land-use change are reshuffling the distribution of wild organisms on a global scale. Some species may expand their ranges and colonize new regions, which may greatly affect ecological interactions among pre-existing species and colonizers. In the last decades, such processes have originated a unique condition of sympatry among three Eurasian small Falco species (common kestrel F. tinnunculus, lesser kestrel F. naumanni, red-footed falcon F. vespertinus) in the intensively cultivated farmland habitats of the Po Plain (Northern Italy). This provides an excellent opportunity to investigate patterns of spatial niche overlap during the initial phases of the establishment of sympatry. To investigate spatial niche overlap of the three falcon species, we relied on Environmental Niche Models (ENMs) based on widespread breeding occurrence data obtained through field surveys and citizen science programs (during the 2018–2020 period). ENMs were based on bioclimatic and land-use variables in an ensemble modelling framework. We estimated species-specific relative contributions of each climatic and land-use variable and its response curves effect. Eventually, we generated spatial correlation maps of the potential species’ distributions to derive spatially-explicit predictions of potential co-occurrence areas among the three species. Overall, eco-climatic determinants of the distribution of lesser kestrel and red-footed falcon were similar, resulting in a strong association with intensive arable lands and dry continental climate. Consistently, we found a high spatial correlation between the suitability maps of the two species, with highly suitable areas located in the Central-Eastern area of the Po Plain, corresponding to the core range of both species. Conversely, the common kestrel emerged as a habitat generalist and was widely distributed throughout the Po Plain. Our findings suggest that the recent sympatry between lesser kestrels and red-footed falcons in the Po Plain may promote ecological interactions and intra-guild competition.

Predator niche overlap and partitioning and potential interactions in the mountains of Central Asia

AbstractDirect and indirect interactions among predators affect predator fitness, distribution, and overall community structure. Yet, outside of experimental settings, such interactions are difficult to observe and thus poorly understood. Patterns of niche overlap among predators reflect and shape community interactions and may therefore help elucidate the nature and intensity of intraguild interactions. To better understand the coexistence of two apex predators, snow leopards (Panthera uncia) and wolves (Canis lupus), we investigated their spatial, temporal, and dietary niche overlap in summer in the Pamir Mountains of Tajikistan. We estimated population-level space use via spatial capture–recapture models based on noninvasive genetics and camera traps, diel activity patterns based on camera trap detections, and diet composition from prey remains in carnivore scats, from which we estimated coefficients between 0 and 1 for overlap in space, time, and diet, respectively. Snow leopards and wolves displayed moderate spatial partitioning (0.26, 95% confidence interval [CI]: 0.17–37), but overlapping temporal (0.77, 95% CI: 0.64–0.90) and dietary (0.97, 95% CI: 0.80–0.99) niches. Both predators relied on seasonally abundant marmots (Marmota caudata) rather than wild ungulates, their typical primary prey, suggesting that despite patterns of overlap that were superficially conducive to exploitation competition and predator facilitation, prey were likely not a limiting factor. Therefore, prey-mediated interactions, if present, were unlikely to be a major structuring force in the ecosystem. By implication, carnivore conservation planning and monitoring in the mountains of Central Asia should more fully account for the seasonal importance of marmots in the ecosystem.

种间互作对雷州湾海域鱼类群落结构的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 种间互作对雷州湾海域鱼类群落结构的影响 DOI: 10.5846/stxb202108212330 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划"蓝色粮仓科技创新"重点专项资助（2020YFD0901103）；南方海洋科学与工程广东省实验室（湛江）资助项目（ZJW-2019-06） Importance of species interactions in structuring fish community of Leizhou Bay waters, northern South China Sea Author: Affiliation: Fund Project: The National Basic Research Program of China (973 Program),其他 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:从鱼类种间互作及其生态网络特征视角研究鱼类群落结构特征，对解析多鱼种共存机制和基于群落水平的多鱼种资源管理均具有重要意义。为分析鱼类资源利用的竞争互作对群落结构稳定性的影响，根据2016-2018年8个航次的雷州湾海域底拖网调查的鱼类数据，将空间生态位重叠理论和生态网络建模相结合，从种间互作的角度应用加权聚类系数C、加权平均路径长度A、关联度Co等指标分析鱼类的群落结构。结果表明：①鱼类生态位重叠所形成的种间互作网络季节变动较大，而年度变动则相对较小，共包含鱼类58-122种，种间互作的关系数量1318-7103。②雷州湾海域鱼类群落内种间互作密集，聚合程度高（C介于0.84-0.98）且能量传递效率高（A介于0.02-0.09），呈现互作弱化之趋势（Co介于0.32-0.48），群落结构总体较稳定。③小尺度范围（20°40'-21°00'N，110°30'-110°45'E）内，鱼类群落内种间互作特征是维持多种鱼类共存的重要内因。该特征表现为季节和年度的变化总体上相似，种间直接关联程度与种间互作强度呈正相关（P<0.01），而局部聚合程度与种间直接关联、互作强度均呈负相关（P<0.01）。本研究可为鱼类群落结构稳定性的量化评价和资源养护的管理规划提供参考依据。 Abstract:The interactions between fish species and their roles in the ecological network on structuring the fish community is a matter of great concern not only for understanding the species coexistence, but also for the multispecies fishery management and conservation at the community level. The data from the bottom trawl surveys of eight cruises in Leizhou Bay waters northern South China Sea during 2016 and 2018 were applied to analyze how the species interactions (interspecific competition in limited resources and space) affected the stability of fish community structure in seasons and years. Combining theories on spatial niche overlap and the ecological network modeling, six indicators such as the weighted clustering coefficient (C), weighted average path length (A), connectance (Co), degree (K), weighted node strength (Si), and locally weighted clustering coefficient (Ci) were respectively applied to measure the degree of community aggregation, the overall energy transfer efficiencies between species, interspecific connectivity, the degree of directly interspecific associations, the intensity of species interactions, and the degree of local aggregation between species. And then we analyzed the importance of species interactions in structuring fish community of Leizhou Bay waters. The results showed that:①the network of species interaction which formed by spatial niche overlap of fishes varied more widely in seasons, but comparatively minor between years, including 58-122 kinds of fishes, and 1318-7103 lines (links between species interactions). ②The fish community was characterized with the intensive interactions, high degrees of aggregation (C ranged between 0.84 and 0.98), high energy transfer efficiencies (A ranged between 0.02 and 0.09), with a weakening tendency of species interactions (Co ranged between 0.32 and 0.48) from 2016 to 2018. The fish community of Leizhou Bay waters was kept in a state of stability in all. ③At the local small scale (20°40'-21°00'N, 110°30'-110°45'E), traits of species interactions of the fish community were similar on the seasonal and annual scale. Two traits were the important internal factors driving the coexistence of multiple fish species in the Leizhou Bay waters. The first was the degree of directly interspecific associations which was positively correlated with the intensity of species interactions (P<0.01). And the second was the degree of local aggregation which was negatively correlated with both the degree of directly interspecific associations and the intensity of species interactions (P<0.01). This study provides clues for the quantitative analysis on the stability of fish community structure and planning of effective coastal fishery resources management and conservation. 参考文献 相似文献 引证文献

Spatial and functional niche overlap between invasive Ligustrum lucidum and native woody species in an urban shrine forest in Japan

Spatial and functional niche overlap between invasive Ligustrum lucidum and native woody species in an urban shrine forest in Japan

Niche overlap and species co-occurrence patterns in carabid communities of the northern Chinese steppes.

Understanding how species sort themselves into communities is essential to explain the mechanisms that maintain biodiversity. Important insights into potential mechanisms of coexistence may be obtained from observation of non-random patterns in community assembly. The spatial niche overlap (Pianka index) and co-occurrence (c-score) patterns in carabid species in three types of steppes (desert steppe, typical steppe, and meadow steppe) in China was investigated. Non randomness was tested using null models. Niche overlap values were significantly higher than expected by chance in the desert steppe, where vegetation cover is less abundant and less uniformly distributed, which possibly forces species to concentrate in certain places. In the typical and meadow steppes, results were influenced by the scale of the analysis. At a broad scale, niche separation was found as a result of species segregation among different sectors (habitats) within these steppes, but when the analysis was conducted at a finer scale, species appeared to be no more segregated than expected by chance. The high co-occurrence averages found in the meadow and typical steppes indicate that the distributions of the species found in a site may be negatively affected by the presence of other species, which suggests that some species tend to exclude (or reduce the abundance of) others. The very low c-score average observed in the desert steppe suggests that competition is not involved there. Thus, in more homogeneous landscapes (such as the typical and meadow steppes), competition might play some role in community structure, whereas spatial variation in the abundances of species is more driven by the uneven spatial distribution of vegetation in the landscape where productivity is lower and less uniformly distributed.

Spatio-temporal niche of major fish species in Pishan waters off Zhejiang Province, China.

Based on seasonal bottom trawl surveys in November 2015 (autumn), February (winter), May (spring) and August (summer) in 2016, the index of relative importance (IRI), Shannon index and Pianka index were used to analyze the breadth and overlap of spatio-temporal niche of major fish species in the Pishan waters off Zhejiang Province. Redundancy analysis and interspecific competition coefficient were used to examine the competition relationship and niche differentiation of those major fish species. The results showed that a total of 61 fish species were recorded throughout the year, which belonged to 13 orders, 29 families and 48 genera. A total of 19 species with IRI&gt;100 were identified as major fish species. The temporal niche overlap value between Chelidonichthys kumu and Atule kalla was largest, indicating high temporal synchronization. Both the spatial niche overlap value and the spatio-temporal niche overlap value between Trpauchen vagina and Cynoglossus interruptus were largest, indicating that their spatial homology was high and that the use of spatial and temporal two-dimensional resource of both species were consistent. The percentage of species pairs with spatio-temporal niche overlap at the significant level (Qik&gt;0.6) was only 5.8% in Pishan waters, indicating that the spatial and temporal distribution of those species were quite different. The overlap of spatio-temporal niche significantly varied across different seasons. The results of the interspecific competition coefficient were basically consistent with the niche overlap. Results of the redundancy analysis revealed the relationships between major fish species and environmental factors (temperature, salinity, dissolved oxygen), and further explained the niche diffe-rentiation among species.

Habitat use and spatial niche overlap of sympatric savannah tortoises at multiple spatial scales in South Sudan

Tortoise ecology is poorly studied in East Africa. Here, using two terrestrial Testudinidae (Stigmochelys pardalis and Kinixys belliana) as study models, we (i) present basic demographic characteristics (sex-ratio, and density), (ii) describe correlates of their presence at two spatial scales (micro-habitat and macro-habitat), (iii) evaluate the effects of rainfall on their seasonal activity patterns, and (iv) analyze abundance patterns in relation to macro- and micro-habitat characteristics. We also describe an experiment, using tortoise shells, that can allow to control, and eventually correct, the reliability of observed data by taking into account the detectability of the study species in the wild. On the basis of a suite of statistical analysis and GIS-based elaborations, we confirmed, and further uncovered, the remarkable ecological differences existing between S. pardalis and K. belliana. The habitat use was different interspecifically, with K. belliana being much more linked to dense vegetation spots, often nearby waterbodies, whereas S. pardalis being an habitat generalist, at both micro- and macrohabitat scale. Nonetheless, juveniles of both species were observed in areas with significantly higher % soil covered by vegetation taller than 200 cm than adults of both sexes. This different habitat selection is hypothesized to be due to antipredatory reasons. Overall, our data suggests that interspecific competition should be minimal between these species.