昆承湖优势种鱼类时空-营养生态位

为了解昆承湖优势种鱼类资源利用情况,首先利用生态位方法计算了时间、空间及营养三个资源维度的生态位宽度及重叠值,然后根据时空-营养生态位宽度值将优势种鱼类划分为广位种、中位种和窄位种,最后讨论了生态位宽度及重叠的可能原因。结果显示：刀鲚Coilia nasus、蒙古鲌Chanodichthys mongolicus、似鱎Toxabramis swinhonis、似鳊Pseudobrama simoni、鳙Hypophthalmichthys nobilis、鲢Hypophthalmichthys molitrix、花鱼骨Hemibarbus maculatus、似刺鳊鮈Paracanthobrama guichenoti、大鳍鱊Acheilognathus macropterus和鲫Carassius auratus为优势种。在时间维度：鲢的生态位宽度最大,似鳊的最小;生态位重叠具有显著意义的有24对,占总的53.33%。在空间维度,似刺鳊鮈最大,鲢最小;生态位重叠具有显著意义的有36对,占总的80%。在营养维度,最大的为鲫,最小的为花鱼骨;生态位重叠具有显著意义的有8对,占17.78%...     

Trophic niche similarities of sympatric Turdus thrushes determined by fecal contents,stable isotopes,and bipartite network approaches

An ecological niche has been defined as an n‐dimensional hypervolume formed by conditions and resources that species need to survive, grow, and reproduce. In practice, such niche dimensions are measurable and describe how species share resources, which has been thought to be a crucial mechanism for coexistence and a major driver of broad biodiversity patterns. Here, we investigate resource partitioning and trophic interactions of three sympatric, phylogenetically related and morphologically similar species of thrushes (Turdus spp.). Based on one year of data collected in southern Brazil, we investigated niche partitioning using three approaches: diet and trophic niche assessed by fecal analysis, diet and niche estimated by stable isotopes in blood and mixing models, and bipartite network analysis derived from direct diet and mixing model outputs. Approaches revealed that the three sympatric thrushes are generalists that feed on similar diets, demonstrating high niche overlap. Fruits from C3 plants were one of the most important food items in their networks, with wide links connecting the three thrush species. Turdus amaurochalinus and T. albicollis had the greatest trophic and isotopic niche overlap, with 90% and 20% overlap, respectively. There was partitioning of key resources between these two species, with a shared preference for fig tree fruits—Ficus cestrifolia (T. amaurochalinus PSIRI% = 11.3 and T. albicollis = 11.5), which was not present in the diet of T. rufiventris. Results added a new approach to the network analysis based on values from the stable isotope mixing models, allowing comparisons between traditional dietary analysis and diet inferred by isotopic mixing models, which reflects food items effectively assimilated in consumer tissues. Both are visualized in bipartite networks and show food‐consumers link strengths. This approach could be useful to other studies using stable isotopes coupled to network analysis, particularly useful in sympatric species with similar niches.     

Trophic niche partitioning between two prey and their incidental predators revealed various threats for an endangered species

Documenting trophic niche partitioning and resource use within a community is critical to evaluate underlying mechanisms of coexistence, competition, or predation. Detailed knowledge about foraging is essential as it may influence the vital rates, which, in turn, can affect trophic relationships between species, and population dynamics. The aims of this study were to evaluate resource and trophic niche partitioning in summer/autumn between the endangered Atlantic‐Gaspésie caribou (Rangifer tarandus caribou) population, moose (Alces americanus) and their incidental predators, the black bear (Ursus americanus) and coyote (Canis latrans), and to quantify the extent to which these predators consumed caribou. Bayesian isotopic analysis showed a small overlap in trophic niche for the two sympatric ungulates suggesting a low potential for resource competition. Our results also revealed that caribou occupied a larger isotopic niche area than moose, suggesting a greater diversity of resources used by caribou. Not surprisingly, coyotes consumed mainly deer (Odocoileus virginianus), moose, snowshoe hare (Lepus americanus), and occasionally caribou, while bears consumed mainly vegetation and, to a lesser extent, moose and caribou. As coyotes and bears also feed on plant species, we documented trophic niche overlap between caribou and their predators, as searching for similar resources can force them to use the same habitats and thus increase the encounter rate and, ultimately, mortality risk for caribou. Although the decline in the Gaspésie caribou population is mostly driven by habitat‐mediated predation, we found evidence that the low level of resource competition with moose, added to the shared resources with incidental predators, mainly bears, may contribute to jeopardize the recovery of this endangered caribou population. Highlighting the trophic interaction between species is needed to establish efficient conservation and management strategies to insure the persistence of endangered populations. The comparison of trophic niches of species sharing the same habitat or resources is fundamental to evaluate the mechanisms of coexistence or competition and eventually predict the consequences of ecosystem changes in the community.     

Stable isotope analyses reveal dense trophic species packing and clear niche differentiation in a malagasy primate community

Understanding the mechanisms maintaining local species richness is a major topic in tropical ecology. In ecological communities of Madagascar, primates represent a major part of mammalian diversity and, thus, are a suitable taxon to study these mechanisms. Previous research suggested that ecological niche differentiation facilitates the coexistence of lemurs. However, detailed data on all species making up diverse local primate assemblages is rarely available, hampering community‐wide tests of niche differentiation among Malagasy mammals. Here, we took an indirect approach and used stable isotopes as long‐term indicators of individuals' diets to answer the question of whether trophic patterns and food‐related mechanisms stabilize coexistence in a species‐rich lemur community. We analyzed stable carbon and nitrogen isotopes in hair collected from eight syntopic lemurs in Kirindy Forest. We found that lemur species were well separated into trophic niches and ranged over two trophic levels. Furthermore, species were densely packed in isotopic space suggesting that past competitive interactions between species are a major structuring force of this dry forest lemur community. Results of other comparative studies on primates and our findings underline that—in contrast to communities worldwide—the structure and composition of lemur communities follow predictions of ecological niche theory. Patterns of competitive interactions might be more clearly revealed in Malagasy primate communities than elsewhere because lemurs represent a large fraction of ecologically interacting species in these communities. The pronounced trophic niche differentiation among lemurs is most likely due to intense competition in the past as is characteristic for adaptive radiations. Am J Phys Anthropol 153:249–259, 2014. © 2013 Wiley Periodicals, Inc.     

Isotopic niche mirrors trophic niche in a vertebrate island invader

Caution for the indiscriminate conversion of the isotopic niche into ecologic niche was recently advised. We tested the utility of the isotopic niche to answer ecological questions on oceanic islands. We compared the isotopic niches of black rats (Rattus rattus) on two islands in the Gulf of California, Mexico: Farrallón de San Ignacio (FSI) and San Pedro Mártir (SPM). Both islands maintained several species of marine birds, but FSI is devoid of terrestrial vegetation and SPM has several species of terrestrial plants. We tested the hypothesis that rats on FSI have a narrower trophic niche due to its lower diversity of food items. We predicted a smaller variance in δ¹³C and δ¹⁵N values of rat muscle on FSI, and a lower use of marine birds as food on SPM. We also examined stomach contents of rats on both islands to validate the isotopic information. Variances in δ¹³C and δ¹⁵N values of black rats were lower on FSI, and the contribution of marine birds to the diet of rats was smaller on SPM. Stomachs in most rats collected on FSI contained only one or two types of food items, mostly marine birds and terrestrial invertebrates. In contrast, stomachs with only one type of food item were rare on SPM, and in most cases they contained three or more food types. Our findings showed that isotopic variance is a good approximation for trophic niche when comparing populations with access to an assemblage of preys with contrasting biological and isotopic diversity.     

Trophic specialization influences the rate of environmental niche evolution in damselfishes (Pomacentridae)

The rate of environmental niche evolution describes the capability of species to explore the available environmental space and is known to vary among species owing to lineage-specific factors. Trophic specialization is a main force driving species evolution and is responsible for classical examples of adaptive radiations in fishes. We investigate the effect of trophic specialization on the rate of environmental niche evolution in the damselfish, Pomacentridae, which is an important family of tropical reef fishes. First, phylogenetic niche conservatism is not detected in the family using a standard test of phylogenetic signal, and we demonstrate that the environmental niches of damselfishes that differ in trophic specialization are not equivalent while they still overlap at their mean values. Second, we estimate the relative rates of niche evolution on the phylogenetic tree and show the heterogeneity among rates of environmental niche evolution of the three trophic groups. We suggest that behavioural characteristics related to trophic specialization can constrain the evolution of the environmental niche and lead to conserved niches in specialist lineages. Our results show the extent of influence of several traits on the evolution of the environmental niche and shed new light on the evolution of damselfishes, which is a key lineage in current efforts to conserve biodiversity in coral reefs.     

Beyond ecological opportunity: Prey diversity rather than abundance shapes predator niche variation

1. Ecological opportunity (i.e. the diversity of available resources) has a pivotal role in shaping niche variation and trophic specialisation of animals. However, ecological opportunity can be described with regard to both diversity and abundance of resources. The degree to which these two components contribute to niche variation remains unexplored.
2. To address this, we used an extensive dataset on fish diet and benthic invertebrate diversity and density from 73 sampling events in three Norwegian rivers in order to explore realised trophic niches and the response of dietary niche variation along gradients of resource diversity (potential trophic niches), resource density (as a proxy of resource abundance) and fish density (as a proxy of inter‐ and intra‐specific competition) in a freshwater top predator (the brown trout, Salmo trutta L.).
3. Linear models indicated that individual and population niche variation increased with increasing ecological opportunity in terms of prey diversity. However, no simple cause‐and‐effect associations between niche indices and prey abundance were found. Our multiple regression analyses indicated that the abundance of certain resources (e.g. Chironomidae) can interact with prey diversity to determine individual and population realised trophic niches. Niche variation (within‐individual component and inter‐individual diet variation) decreased with increasing inter‐ and intra‐specific competition.
4. This study extends prevailing trophic ecology theory by identifying diversity, rather than density, of available prey resources as a primary driver of niche variation in fish of temperate riverine systems with no extensive resource limitation. The study also shows that ecological opportunity may mask the direction of the effect (compression or expansion) of competition on niche variation when food resources are diverse.
5. Our study provides novel empirical insight to the driving forces behind niche variation and reveals that diversity, rather than density, of available prey resources may be a primary driver of niche variation in freshwater fish. Our study supports the view that a broader potential trophic niche promotes broader realised trophic niche variation by individuals, which leads to individual niche diversification by opening access to alternatives resources, resulting in a concomitant rise in the realised trophic niche width of the population.

     

Impacts of zebra mussels (Dreissena polymorpha) on isotopic niche size and niche overlap among fish species in a mesotrophic lake

Zebra mussels (Dreissena polymorpha) filter feed phytoplankton and reduce available pelagic energy, potentially driving fish to use littoral energy sources in lakes. However, changes in food webs and energy flow in complex fish communities after zebra mussel establishment are poorly known. We assessed impacts of zebra mussels on fish littoral carbon use, trophic position, isotopic niche size, and isotopic niche overlap among individual fish species using δ¹³C and δ¹⁵N data collected before (2014) and after (2019) zebra mussel establishment in Lake Ida, MN. Isotope data were collected from 11 fish species, and from zooplankton and littoral invertebrates to estimate baseline isotope values. Mixing models were used to convert fish δ¹³C and δ¹⁵N into estimates of littoral carbon and trophic position, respectively. We tested whether trophic position, littoral carbon use, isotopic niche size, and isotopic niche overlap changed from 2014 to 2019 for each fish species. We found few effects on fish trophic position, but 10 out of 11 fish species increased littoral carbon use after zebra mussel establishment, with mean littoral carbon increasing from 43% before to 67% after establishment. Average isotopic niche size of individual species increased significantly (2.1-fold) post zebra mussels, and pairwise-niche overlap between species increased significantly (1.2-fold). These results indicate zebra mussels increase littoral energy dependence in the fish community, resulting in larger individual isotopic niches and increased isotopic niche overlap. These effects may increase interspecific competition among fish species and could ultimately result in reduced abundance of species less able to utilize littoral energy sources.

     

Seabird species‐ and assemblage‐level isotopic niche shifts associated with changing prey availability during breeding in coastal Newfoundland

Shifting prey availability can lead to altered species interactions, indicated by variation in the dietary niche breadth and position of species within an assemblage. On the Newfoundland coast, annual inshore spawning migration of the dominant forage fish, Capelin Mallotus villosus, provides an excellent opportunity to investigate the influence of varying prey availability on dietary niche breadth and position among species. During June–August 2017, we investigated species‐ and assemblage‐level dietary responses to shifting Capelin availability of three Capelin‐eating, sympatrically breeding auk species, the Atlantic Puffin Fratercula arctica, Razorbill Alca torda and Common Murre Uria aalge. The diet of Leach's Storm Petrels Oceanodroma leucorhoa, which breed alongside the three auk species but are not known to rely on Capelin, was also examined to determine dietary shifts throughout breeding that were unrelated to Capelin availability. We quantified stable isotope ratios (δ¹⁵N, δ¹³C) in seabird blood components (plasma, cellular component) collected both before and after spawning Capelin arrived in the study area and compared isotopic niche breadth within a Bayesian framework. At the species level, auk trophic position increased and isotopic niche breadth narrowed after Capelin arrived, suggesting a more Capelin‐based diet. Simultaneously, trophic diversity of the auk assemblage, reflecting the extent of spacing among niches of species, decreased after spawning Capelin arrived inshore. Contrastingly, increased trophic position but broader isotopic niche breadth during higher relative to lower Capelin availability for Leach's Storm Petrel confirm that this species is probably not affected by the inshore arrival of Capelin, but instead that isotopic changes may be more related to a shift in breeding stage to chick‐rearing. Overall, our findings reiterate the importance of Capelin as a prey resource for breeding auks in coastal Newfoundland, but that the degree of reliance on Capelin varies among species, possibly allowing coexistence of these ecologically similar species. The findings highlight potential changing species interactions, such as increased competition, under declines in Capelin biomass.     

Seasonal dietary niche contraction in coexisting Neotropical frugivorous bats (Stenodermatinae)

Tropical dry forests are characterized by punctuated seasonal precipitation patterns that drive primary production and the availability of fruits, seeds, flowers, and insects throughout the year. In environments in which the quantity and quality of food resources varies seasonally, consumers should adjust their foraging behavior to maximize energy intake while minimizing overlap with competitors during periods of low food availability. Here, we investigated how the diets of frugivorous bats in tropical dry forests of NW Mexico varied in response to seasonal availability and how this affected dietary overlap of morphologically similar species. We performed stable isotope analyses to understand temporal and interspecific patterns of overall isotopic niche breadth, trophic position, and niche overlap in the diet of six frugivorous species of closely related New World leaf-nosed bats (family Phyllostomidae, subfamily Stenodermatinae). We estimated seasonal changes in resource abundance in two complementary ways: (a) vegetative phenology based on long-term remote sensing data and (b) observational data on food availability from previously published insect and plant fruiting surveys. In all species, there was a consistent pattern of reduced isotopic niche breadth during periods of low food availability. However, patterns of niche overlap varied between morphologically similar species. Overall, results from our study and others suggest that seasonal food availability likely determines overall dietary niche breadth in Phyllostomidae and that despite morphological specialization, it is likely that other mechanisms, such as opportunistic foraging and spatiotemporal niche segregation, may play a role in maintaining coexistence rather than simply dietary displacement.     

Global test of Eltonian niche conservatism of nonnative freshwater fish species between their native and introduced ranges

Despite growing evidence that biotic interactions limit the distribution of species and their potential redistribution under climate change, the recent surge of interest in niche conservatism has predominantly focused on the Grinellian (abiotic) niche, whereas few studies have attempted to quantify potential lability in the Eltonian (biotic or trophic) niche. Here, we test for conservatism in the Eltonian niche of 32 freshwater fish species between their introduced and native ranges from 435 populations across the globe. We used stable isotope data to quantify niche shifts along the horizontal (δ¹³C: indicating the origin of the resources consumed) and vertical (δ¹⁵N: describing the trophic position) dimensions of the isotopic niche, as well as shifts in overall isotopic niche breadth. Using an assemblage centroid standardized isotope vector analysis and controlling for phylogenetic relatedness among species, we demonstrated that introduced freshwater fishes exhibited flexibility in both resource use and trophic position that was beyond levels of natural variability observed in their native ranges. By contrast, niche breadth showed variability only within the limits recorded in native populations and varied independently from shifts in mean isotopic niche positions. Across all species and introduction histories, we found a consistent shift towards more balanced acquisition of resources with mixed origins and at intermediate trophic positions, suggesting a general mechanism by which fish species successfully establish into recipient communities. The mechanisms that promote or inhibit species from shifting their Eltonian niche remains unknown, but trophic flexibility is likely to contribute to both the success and the ecological impacts of invasive species and range shifts of native species under future global change.     

More rapid shift to a benthic niche in larger Gadus morhua juveniles

Trophic use by Atlantic cod Gadus morhua juveniles was examined early and late in the shift from pelagic to benthic habitats. Changes in the proportion of pelagic copepods, estimates of benthic prey indicated by isotope mixing models and stable‐isotope values between sample periods suggested a gradual shift towards a benthic niche. Values of the trophic proxies, however, changed most markedly in the largest juvenile group, suggesting a more rapid trophic niche shift, and in turn competitive advantage, of larger juveniles.     

Non-linear relationship between body size of terrestrial carnivores and their trophic niche breadth and overlap

Studying food partitioning of mammalian predators is important for understanding trophic structures and interactions between coexisting carnivore species. This is particularly pertinent in the light of expanding ranges of populations of generalist species whose habitat and diet overlap with more specialized species. Here, we tested the resource partitioning hypothesis in terrestrial carnivores, predicting that trophic niche breadth and overlap relate positively to body mass. We used dietary data from 18 terrestrial carnivore taxa in four families (Canidae, Mustelidae, Felidae and Ursidae; body mass 0.1–173.6 kg) in three regions in Central and Eastern Europe, i.e. deciduous forest and forest-steppe region (DFR), temperate deciduous and mixed forest region (MFR) and transitory mixed forest regions (TFR). We ranked carnivores along an axis of trophic niche (breadth and overlap), and analysed the relationship between trophic niche and body mass (or pair-wise difference in body mass). A hierarchical cluster analysis of diet composition divided carnivores into four ecological groups: wild ungulate predators; small-mammal predators; amphibians and small mammal predators and omnivores. The relationship between body mass of predators and both trophic niche breadth and trophic niche overlap were hump-shaped. The trophic niche breadth to body mass ratio was significantly lower in DFR than in TFR and trophic niche overlap was significantly higher in DFR than in MFR and TFR. The predominant food resource is small mammals whose abundance is related to local agricultural and forestry management practices. Modifications of management techniques can affect population dynamics and community composition of carnivore species, especially in the case of small-mammal predators.     

Stable isotopes indicate that zebra mussels (Dreissena polymorpha) increase dependence of lake food webs on littoral energy sources

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Grassland harvesting alters ant community trophic structure: An isotopic study in tallgrass prairies

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喜马拉雅山南坡蚤类营养生态位的研究

对喜马拉雅山南坡地区的46种蚤的营养生态位宽度和生态位重叠进行了研究。结果表明,23种蚤只有1种宿主,其营养生态位宽度最窄(B=0),而方指双蚤的营养生态位宽度最大(B=0.6694),其次为斯氏新蚤(B=0.4968).寄生于9种小兽宿主的12种主要蚤种中,尼泊尔古蚤和后厉蚤和窄突厉蚤因其宿主动物以食虫类为主,相互间的营养生态位重叠指数最高。     

Measurement of trophic niche breadth using occurrence frequencies

A modification of Gladfelter-Johnson's index to measure trophic niche breadth using occurrence frequencies is proposed, in order to make it more sensitive to different resource use patterns. The new index ranges from 0 to 1 and measures niche breadth in a guild context.     

Stable isotopes are quantitative indicators of trophic niche

Hette‐Tronquart (2019, Ecol. Lett.) raises three concerns about our interpretation of stable isotope data in Sheppard et al. (2018, Ecol. Lett., 21, 665). We feel that these concerns are based on comparisons that are unreasonable or ignore the ecological context from which the data were collected. Stable isotope ratios provide a quantitative indication of, rather than being exactly equivalent to, trophic niche.     

A multivariate approach reveals diversity of ontogenetic niche shifts across taxonomic and functional groups

1. Shifts in the fundamental and realised niche of individuals during their ontogeny are ubiquitous in nature, but we know little about what aspects of the niche change and how these changes vary across species within communities. However, this knowledge is essential to predict the dynamics of populations and communities and how they respond to environmental change.
2. Here I introduce a range of metrics to describe different aspects of shifts in the realised trophic niche of individuals based on stable isotopes. Applying this multi-variate approach to 2,272 individuals from 13 taxonomic and functional distinct species (Amphibia, Hemiptera, Coleoptera, Odonata) sampled in natural pond communities allowed me to: (1) describe and quantify the diversity of trophic niche shift patterns over ontogeny in multi-dimensional space, and (2) identify what aspects of ontogenetic shifts vary across taxa, and functional groups.
3. Results revealed that species can differ substantially in which aspects of the trophic niche change and how they change over ontogeny. Interestingly, patterns of ontogenetic niche shifts grouped in distinct taxonomic clusters in multi-variate space, including two distinct groups of predators (Hemiptera versus Odonata). Given the differences in traits (especially feeding mode) across groups, this suggests that differences in ontogenetic niche shifts across species could at least partially be explained by variation in traits and functional roles of species.
4. These results emphasise the importance of a multivariate approach to capture the large diversity of trophic niche shifts patterns possible in natural communities and suggest that differences in ontogenetic niche shifts follow general patterns.

     

东太平洋中部中上层鲨鱼群落营养生态位分化

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