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28 results for “niche width”
Data for: Population niche width is driven by within-individual niche expansion and individual specialization in introduced brook trout in mountain lakes
<p><span>The width of a population's resource use niche is determined by individual diet breadth ("within-individual component") and the degree of niche partitioning between individuals ("between-individual component"). The balance between these two factors affects ecological stability and evolutionary trajectories, and may shift as ecological opportunity permits broader population niches. Lakes in California's Sierra Nevada Mountains vary in resource diversity for introduced brook trout (<em>Salvelinus fontinalis</em>) due to elevation, lake morphometry, and watershed features. We compared the relative contributions of within- and between-individual niche components to two measures of the dietary niches of thirteen populations of brook trout: prey taxonomic composition and prey size distribution. For both taxonomic and size diversity of fish diets, population niche width was positively related to both the within- and between-individual components. For taxonomic diversity, the two components increased in parallel, while for size diversity, the between-individual component became more important relative to the within-individual component in populations with the greatest niche widths. Our results support the Niche Variation Hypothesis that populations with broader niches are more heterogeneous among individuals and show that individual niche width and individual specialization can operate in parallel to expand the population niche.</span></p>
Рис. 2. Ширина трофической ниши паукообразных в биотопах трех типов: I – поΛупустынная равнина; II – каменистые скΛоны пΛато; III – ΔоΛина со скопΛениями скаΛьных останцев. Fig. 2. The width of the trophic niche of arachnids in biotopes of three types: I – semidesert plain; II – stony slopes of the plateau; III – valley with clusters of rocks. in Comparison of trophic spectra and hunting strategies of some large arachnids (Arachnida: Scorpiones, Solifugae, Aranei) in semi-desert biocenoses of Gobustan (Eastern Azerbaijan)
Рис. 2. Ширина трофической ниши паукообразных в биотопах трех типов: I – поΛупустынная равнина; II – каменистые скΛоны пΛато; III – ΔоΛина со скопΛениями скаΛьных останцев. Fig. 2. The width of the trophic niche of arachnids in biotopes of three types: I – semidesert plain; II – stony slopes of the plateau; III – valley with clusters of rocks.
Data for: Population niche width is driven by within-individual niche expansion and individual specialization in introduced brook trout in mountain lakes
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Seasonal isotopic niche of a rodent: High between-individual variation but no changes in individual niche width during the rich-resource period
<p>The dynamics of trophic niche width in animals at both population- and individual-level is potentially influenced by temporal variation of food resources, by between-individual differences in food-resource rank preferences<span class="fontstyle01"><span>, and also by competition</span></span>. Using stable isotope of carbon and nitrogen (<i>δ</i><sup>13</sup>C and <i>δ</i><sup>15</sup>N) of fecal samples, we investigated the trophic niche dynamics and individual variation in food-resource use by the arboreal rat <i>Rhipidomys macrurus</i>, in the highly seasonal Brazilian savanna (Cerrado). We tested the hypothesis that dietary niche expansion during the rich-resource period (wet season) occurs via individual specialization and consequently lower individual niche overlap in contrast with niche retraction during the low-resource period (dry season) via increase in niche overlap and expansion of individual niches. The results indicated that <i>R</i>.<i> macrurus</i> is primarily frugivorous and presents a wider isotopic niche in the rich-resource period in comparison to the low-resource period. The increase in niche width was achieved by individual specialization (decrease in niche overlap), as expected. During the low-resource period, however, individual niche widths were not wider than during the rich-resource period. Additionally, individual body condition was lower in the wet season than in the dry season, suggesting higher competition in this period. We conclude that an increase in the population niche may involve only between-individual variation and not necessarily requiring changes in individual niche width. We propose that the combination of ecological opportunity (high resource diversity) in addition to a greater competition in the warm-wet season leads to expansion of the population trophic niche width via individual specialization. </p>
Seasonal isotopic niche of a rodent: High between-individual variation but no changes in individual niche width during the rich-resource period
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Leaf physiological plasticity in Schima superba and Schima argentea is related to ecological niche width under varied altitude gradients
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Data from: Expanded consumer niche widths may signal an early response to spatial protection
<p class="Normal1">Marine management interventions are increasingly being implemented with the explicit goal of rebuilding ocean ecosystems, but early responses may begin with alterations in ecological interactions preceding detectable changes in population-level characteristics. To establish a baseline from which to monitor the effects of spatial protection on reef fish trophic ecology and track future ecosystem-level changes, we quantified temperate reef fish densities, size, biomass, diets and isotopic signatures at nine sites nested within two fished and one five-year old marine protected area (MPA) on the northwest coast of Canada. We calculated rockfish (Sebastes spp.) community and species-specific niche breadth for fished and protected areas based on δ<sup>13</sup>C and δ<sup>15</sup>N values. We found that rockfish community niche width was greater inside the MPA relative to adjacent fished reefs due to an expanded nitrogen range, possibly reflecting early changes in trophic interactions following five years of spatial protection. Our data also demonstrated that the MPA had a positive effect on the δ<sup>15</sup>N signature of rockfish (i.e., trophic position), but the effect of rockfish length on its own was not well-supported. In addition, we found a positive interaction between rockfish length and δ<sup>15</sup>N signature, such that δ<sup>15</sup>N signatures of rockfish caught within the MPA increased more rapidly with body size than those caught in fished areas. Differences in rockfish size structure and biomass among fished and unfished areas were not clearly evident. Species of rockfish and lingcod varied in trophic and size responses, indicating that life-history traits play an important role in predicting MPA effects. These results may suggest early changes in trophic behavior of slow-growing rockfish due to predation risk by faster growing higher trophic level predators such as lingcod inside MPAs established on temperate reefs. Consequently, spatial protection may restore both the trophic and behavioral roles of previously fished consumers earlier and in measurable ways sooner than observable changes in abundance and size.</p>
Data from: Spatial and ecological population genetic structures within two island-endemic Aeonium species of different niche width
The Crassulacean genus Aeonium is a well-known example for plant species radiation on oceanic archipelagos. However, while allopatric speciation among islands is documented for this genus, the role of intra-island speciation due to population divergence by topographical isolation or ecological heterogeneity has not yet been addressed. The aim of this study was to investigate intraspecific genetic structures and to identify spatial and ecological drivers of genetic population differentiation on the island scale. We analyzed inter simple sequence repeat variation within two island-endemic Aeonium species of La Palma: one widespread generalist that covers a large variety of different habitat types (Ae. davidbramwellii) and one narrow ecological specialist (Ae. nobile), in order to assess evolutionary potentials on this island. Gene pool differentiation and genetic diversity patterns were associated with major landscape structures in both species, with phylogeographic implications. However, overall levels of genetic differentiation were low. For the generalist species, outlier loci detection and loci–environment correlation approaches indicated moderate signatures of divergent selection pressures linked to temperature and precipitation variables, while the specialist species missed such patterns. Our data point to incipient differentiation among populations, emphasizing that ecological heterogeneity and topographical structuring within the small scales of an island can foster evolutionary processes. Very likely, such processes have contributed to the radiation of Aeonium on the Canary Islands. There is also support for different evolutionary mechanisms between generalist and specialist species.
The effect of inter-and intraspecific competition on individual and population niche widths – a four-decade study on two interacting salmonids
<p>Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra- and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large-scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build-up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large-scale culling experiment and associated long-term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra- and interspecific competition have large and contrasting impacts on individual and population niches.</p>
Data from: Niche width impacts vertebrate diversification
Aim: The size of the climatic niche of a species is a major factor determining its distribution and evolution. In particular, it has been proposed that niche width should be associated with the rate of species diversification. Here, we test whether species niche width affects the speciation and extinction rates of three main clades of vertebrates: amphibians, mammals and birds. Location: Global. Methods: We obtained the time-calibrated phylogenies, IUCN conservation status, species distribution maps and climatic data for 2340 species of amphibians, 4563 species of mammals and 9823 species of birds. We computed the niche width for each species as the mean annual temperature across the species range. We estimated speciation, extinction and transition rates associated with lineages with either narrow (specialist) or wide (generalist) niches using phylogeny-based birth–death models. We also tested if current conservation status was correlated with the niche width of species. Results: We found higher net diversification rates in specialist species than in generalist species. This result was explained by both higher speciation rates (for the three taxonomic groups) and lower extinction rates (for mammals and birds only) in specialist than in generalist species. In contrast, current specialist species tended to be more threatened than generalist species. Main conclusions: Our diversification analysis shows that the width of the climatic niche is strongly associated with diversification rates and may thus be a crucial factor for understanding the emergence of diversity patterns in vertebrates. The striking difference between our diversification results and current conservation status suggests that the current extinction process may be different from extinction rates estimated from the whole history of the group.
Data from: Species interactions, environmental gradients and body size shape population niche width
<p>Competition for shared resources is commonly assumed to restrict population-level niche width of coexisting species. However, the identity and abundance of coexisting species, the prevailing environmental conditions, and the individual body size may shape the effects of interspecific interactions on species' niche width.</p> <p>Here we study the effects of inter- and intraspecific interactions, lake area and altitude, and fish body size on the trophic niche width and resource use of a generalist predator, the littoral-dwelling large, sparsely-rakered morph of European whitefish (<i>Coregonus lavaretus</i>; hereafter LSR whitefish). We use stable isotope, diet and survey fishing data from 14 subarctic lakes along an environmental gradient in northern Norway.</p> <p>The isotopic niche width of LSR whitefish showed a humped-shaped relationship with increasing relative abundance of sympatric competitors, suggesting widest population niche at intermediate intensity of interspecific interactions. The isotopic niche width of LSR whitefish tended to decrease with increasing altitude, suggesting reduced niche in colder, less productive lakes.</p> <p>LSR whitefish typically shifted to a higher trophic position and increased reliance on littoral food resources with increasing body size, although between-lake differences in ontogenetic niche shifts were evident. In most lakes, LSR whitefish relied less on littoral food resources than coexisting fishes and the niche overlap between sympatric competitors was most evident among relatively large individuals (>250 mm). Individual niche variation was highest among >200 mm long LSR whitefish, which likely have escaped the predation window of sympatric predators.</p> <p>We demonstrate that intermediate intensity of interspecific interactions may broaden species' niche width, whereas strong competition for limited resources and high predation risk may suppress niche width in less productive environments. Acknowledging potential humped-shaped relationships between population niche width and interspecific interactions can help us understand species' responses to environmental disturbance (e.g., climate change and species invasions) as well as the driving forces of niche specialization.</p>
Data from: The effects of spatial scale and isoscape on consumer isotopic niche width
1. The mean and variance of ecological variables are dependent on sampling attributes such as the coverage of environmental heterogeneity (sampling extent) and spatial scale. Trophic niche width is often approximated by bulk tissue stable isotopes of C and N, i.e. the population isotopic niche. However, recent studies suggest that environmental heterogeneity (experienced by individuals) may be more important in defining the isotopic niche width than trophic variability. We hypothesised that isotopic niche width will increase monotonically with spatial scale, largely produced by environmental variation, e.g. nutrient source. 2. To refine this hypothesis, by describing the shapes of isotope scaling curves, we explored a previously published dataset describing three Chilean intertidal species representing different feeding guilds (grazing snails, suspension feeding mussel). We tested these hypotheses on a new, larger dataset describing three functionally-analogous intertidal species from Northern Ireland. We generated isotopic variance-area curves from a spatially-explicit bootstrap and investigated the scale-dependency of environment-isotope relationships, including wave exposure and sub-habitat heterogeneity. 3. Spatial scale explained 50% of the variance in population isotopic niche widths (bivariate C-N ellipse area) by simple, non-linear relationships. Finer scales (< 1 to 10 km lag) accounted for most variance. Scale dependence was strong for ẟ15N variance, of which > 40% was explained by modelling linear coefficients. A ẟ15N baseline gradient, or isoscape, dominated ẟ15N variance scaling patterns, from sheltered, terrestrially-influenced embayments to exposed, pelagic-dominated coastline. Consumer ẟ13C variance had a weaker scale-dependence, plateauing at mesoscales (> 20 km lag). 4. We show that isotopic niche width is strongly dependent on sampling spatial extent, which controls the environmental heterogeneity experienced by individual consumers. Environmental heterogeneity must be accounted for before isotopic niche width can be considered to accurately represent trophic niche width. Studies conducted at different spatial scales are likely to identify different environment-isotope relationships. 5. We recommend that spatial scale should be incorporated into sampling designs explicitly, easiest by maintaining a consistent lag distance or area within which populations are sampled. Identified isoscapes can be de-trended, where necessary.
Data from: Trophic niche width increases with bill size variation in a generalist passerine: a test of the niche variation hypothesis
1. The niche variation hypothesis (NVH) predicts that populations with wider niches are phenotypically more variable than populations with narrower niches, which is frequently used to explain diversifying processes such as ecological release. However, not all empirical evidence supports the NVH. Furthermore, a relationship between population phenotypic variation and niche width can be caused by sexual selection or environmental gradients, which should be carefully considered along with competition in explaining niche variation. 2. In this study we used eight populations of a generalist passerine species, Paradoxornis webbianus (vinous-throated parrotbill), to test the NVH. We assessed evidence of ecological sexual dimorphism and environmental gradients in bill morphology of P. webbianus. A total of 170 P. webbianus from eight sites ranging 24-2,668 m in altitude were included in this study. We used two principal components to quantify bill morphology, one describes bill size and the other describe bill slenderness. We used stable carbon and nitrogen isotope values of bird feathers to quantify trophic positions, and we estimated population trophic niche width using Bayesian standardized ellipse area. 3. Paradoxornis webbianus with larger and more slender bills fed at higher trophic levels and population trophic niche width tended to increase with bill size variation, supporting the NVH. The males had larger bills and marginally higher nitrogen isotope values than the females, suggesting ecological sexual dimorphism. Despite a positive correlation between bill size and wing length indicating sexual selection for larger male size, only three of the eight populations showed both male-biased bill size and male-biased wing length. Sexual dimorphism explained 13%-64% of bill size variation across sites, suggesting its role in niche variation could vary greatly among populations. The variation in bill slenderness in P. webbianus increased with elevation. However, neither bill size variation nor trophic niche width changed with elevation. Therefore, environmental gradients that could be reflected in the elevation are not likely to drive the observed morphological and niche variation. 4. This study provides an empirical case for the NVH and highlights the importance to investigate sexual dimorphism and environmental gradients in the studies of niche dynamics.
Data from: Niche width predicts extinction from climate change and vulnerability of tropical species
<p>Climate change may be a major threat to global biodiversity, especially to tropical species. Yet, why tropical species are more vulnerable to climate change remains unclear. Tropical species are thought to have narrower physiological tolerances to temperature, and they have already experienced a higher estimated frequency of climate-related local extinctions. These two patterns suggest that tropical species are more vulnerable to climate change because they have narrower thermal niche widths. However, no studies have tested whether species with narrower climatic niche widths for temperature have experienced more local extinctions, and if these narrower niche widths can explain the higher frequency of tropical local extinctions. Here, we test these ideas using resurvey data from 538 plant and animal species from 10 studies. We found that mean niche widths among species and the extent of climate change (increase in maximum annual temperatures) together explained most variation (>75%) in the frequency of local extinction among studies. Surprisingly, neither latitude nor occurrence in the tropics alone significantly predicted local extinction among studies, but latitude and niche widths were strongly inversely related. Niche width also significantly predicted local extinction among species, as well as among and (sometimes) within studies. Overall, niche width may offer a relatively simple and accessible predictor of the vulnerability of populations to climate change. Intriguingly, niche width has the best predictive power to explain extinction from global warming when it incorporates coldest yearly temperatures.</p>
Pollinator community and generalisation of pollinator spectra changes with plant niche width and local dominance
<p>Floral traits are assumed to be the main determinants of plants' pollinator spectrum, yet a majority of temperate plant species possess traits allowing for a certain degree of generalisation of their pollinator spectrum. The actual level of pollinator spectrum generalisation is likely to be the result of both plant floral traits and the diversity and abundance of plant species a plant co-occurs with. We expect that plant species co-occurring in highly diverse plant communities should host more generalised pollinator spectra. In the present study, we explore the degree to which the composition and generalisation of plant-pollinator spectra depend on the plant's niche width (measured as co-occurrence with other plant species) and its local dominance (as measured by mean cover in the community). For this purpose, we compiled a database of >250 plant species pollinator spectra from the literature and coupled it with data on plant niche width and local dominance based on the Czech National Phytosociological Database. Species with wider niches had on average more generalised pollinator spectra, ranging from bumblebee-dominated spectra to Diptera- and/or nitidulid beetle-dominated spectra, which was strongly related to plant phylogeny. Plants with bumblebee-dominated spectra had neither wide nor narrow niches. The majority of plants had either muscid-, hoverfly- or nitidulid-dominated or completely generalised pollinator spectra. Among such plants, higher local dominance increased the proportion of opportune muscids in pollinator spectrum, while hoverflies showed the opposite pattern. Honeybees although rather infrequent in pollinator spectra also showed a strong response to locally dominant plant species.</p> <p><em>Synthesis</em>: The composition of a plant's pollinator spectrum is not independent of other aspects of the plant's life-history, namely, niche width and the ability to dominate the community. Wider plant species niches result in more generalised pollinator spectra, supporting our hypothesis that habitat generalists are less prone to specialisation on particular pollinator groups. Conversely, the ability to dominate local plant communities influenced pollinator spectra mainly through specific responses of individual pollinator groups.</p>
Data from: The effects of spatial scale and isoscape on consumer isotopic niche width
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The effect of inter-and intraspecific competition on individual and population niche widths – a four-decade study on two interacting salmonids
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Data from: Trophic niche width increases with bill size variation in a generalist passerine: a test of the niche variation hypothesis
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Pollinator community and generalisation of pollinator spectra changes with plant niche width and local dominance
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Data from: Species interactions, environmental gradients and body size shape population niche width
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