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1,849 result(s) for "breadth"
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Will I stay or will I go? Plant species-specific response and tolerance to high land-use intensity in temperate grassland ecosystems
Aim Intensification of land use strongly impacts plant communities by causing shifts in taxonomic and functional composition. Mechanisms of land use‐induced biodiversity losses have been described for temperate grasslands, but a quantitative assessment of species‐specific occurrence optima and maximum tolerance (niche breadth) to land‐use intensity (LUI) in Central European grasslands is still lacking. Location Temperate, managed permanent grasslands in three regions of Germany. Methods We combined extensive field work with a null model–randomization approach, defined a “habitat niche” for each plant species based on occurrence and abundance across 150 grassland sites differing in LUI (i.e., amount of fertilizer, mowing/grazing intensity and a compound index of these), and assessed their realized niche breadth (tolerance). Underlying mechanisms driving species’ responses to LUI were assessed by relating plant functional traits, Ellenberg indicator values (EIV), Grime's ecological strategies (CSR) and Briemle utilization numbers. Results Out of 151 plant species, 34% responded negatively, whereas 10% responded positively to high LUI. This pattern was mainly driven by species’ response to fertilization and mowing frequency; grazing intensity response was less pronounced. Positively reacting species, displaying broader niches, were associated with competition‐related functional traits, high EIV for nutrient supply and moisture and high mowing tolerance under spatiotemporally variable conditions. Negatively responding species, displaying relatively narrow niches confined to spatiotemporally homogeneous low LUI sites, were associated with a nutrient‐retentive strategy, under nutrient‐poor, base‐rich soil conditions. Conclusion Our analyses of individual species’ reactions clearly demonstrate that species responding negatively to high LUI display little tolerance towards intensive fertilization and mowing, leading to plant diversity loss; whereas grazing partly thwarts these effects by creating new habitat niches and promoting ruderal species. Our approach can be applied to other habitat types and biogeographical regions in order to quantify local specific response or tolerance, adding to existing knowledge about local vegetation dynamics. Employing a combined null model–randomization approach based on species’ occurrence and abundance in temperate grasslands, we calculated plant species‐specific agricultural habitat niches and niche breadths and characterized response‐driving mechanisms by using plant functional and ecological traits. Our approach may be applied to any other habitat type for explaining and predicting community assembly and species coexistence in response to current land‐use practices.
Evolution of Ecological Niche Breadth
How ecological niche breadth evolves is central to adaptation and speciation and has been a topic of perennial interest. Niche breadth evolution research has occurred within environmental, ecological, evolutionary, and biogeographical contexts, and although some generalities have emerged, critical knowledge gaps exist. Performance breadth trade-offs, although long invoked, may not be common determinants of niche breadth evolution or limits. Niche breadth can expand or contract from specialist or generalist lineages, and so specialization need not be an evolutionary dead end. Whether niche breadth determines diversification and distribution breadth and how niche breadth is partitioned among individuals and populations within a species are important but particularly understudied topics. Molecular genetic and phylogenetic techniques have greatly expanded understanding of niche breadth evolution, but field studies of how niche breadth evolves are essential for providing mechanistic details and allowing the development of comprehensive theory and improved prediction of biological responses under global change.
You think you are big fish in a small pond? Perceived overqualification, goal orientations, and proactivity at work
Overqualification denotes situations in which job incumbents have higher qualifications than those required for the job. Drawing on the self-regulatory perspective, we proposed that employees’ perception of overqualification positively affects their proactive behavior through the mechanism of role-breadth self-efficacy and that this indirect effect is moderated by employees’ goal orientations. We tested our hypotheses through two studies. In Study 1, we found that perceived overqualification had a positive indirect effect on employees’ proactive behavior through role-breadth self-efficacy using a sample of 323 salespeople with a cross-lagged panel design. In Study 2, the multi-wave and multi-source data from 302 teachers confirmed the indirect effect and indicated that performance goal orientation and learning goal orientation moderated the indirect relationship.
Most invasive species largely conserve their climatic niche
The ecological niche is a key concept for elucidating patterns of species distributions and developing strategies for conserving biodiversity. However, recent times are seeing a widespread debate whether species niches are conserved across space and time (niche conservatism hypothesis). Biological invasions represent a unique opportunity to test this hypothesis in a short time frame at the global scale. We synthesized empirical findings for 434 invasive species from 86 studies to assess whether invasive species conserve their climatic niche between native and introduced ranges. Although the niche conservatism hypothesis was rejected in most studies, highly contrasting conclusions for the same species between and within studies suggest that the dichotomous conclusions of these studies were sensitive to techniques, assessment criteria, or author preferences. We performed a consistent quantitative analysis of the dynamics between native and introduced climatic niches reported by previous studies. Our results show there is very limited niche expansion between native and introduced ranges, and introduced niches occupy a position similar to native niches in the environmental space. These findings support the niche conservatism hypothesis overall. In particular, introduced niches were narrower for terrestrial animals, species introduced more recently, or species with more native occurrences. Niche similarity was lower for aquatic species, species introduced only intentionally or more recently, or species with fewer introduced occurrences. Climatic niche conservatism for invasive species not only increases our confidence in transferring ecological niche models to new ranges but also supports the use of niche models for forecasting species responses to changing climates.
Combined effects of temperature change and natural habitat on the abundance of arthropod trait syndromes in agroecosystems
Land‐use changes and climatic changes are two entwined stressors on ecosystems. Studies on such interactions often focus on species‐level or region‐specific responses, but fewer have examined differences in responses based on functional traits. Here we examine the influence of natural habitat cover and temperature change on the abundance of all arthropods and on the abundance of pollinator, pest and natural enemy trait syndromes (based on diet breadth, habitat breadth and dispersal mode) in arthropod communities within European agroecosystems. Using a previously compiled dataset along with historical climatic data, we found that all arthropods, diet generalist pollinators and habitat generalist pests were more abundant in sites with a high amount of natural habitat regardless of temperature changes experienced. For diet specialist pollinators, natural habitat and temperature change antagonistically influenced abundance; high amounts of natural habitat in landscapes appeared to mitigate the negative effects of increasing temperature extremes. Habitat specialist pest abundance was higher in sites that experienced greater increases in mean annual temperature, regardless of natural habitat cover. Natural enemies appeared to be more abundant in sites that experienced greater increases in temperature variation. For natural enemies that were flight‐dispersing and habitat generalists this was regardless of natural habitat cover, while for ground‐dispersing natural enemies, temperature change and high natural habitat cover appeared to benefit habitat generalists (ground beetles) and specialists (primarily spiders). Given the variability in responses we observed between different arthropods based on diet breadth, habitat specialism, dispersal ability and functional group, we conclude that functional approaches examining impacts of qualitatively different stressors can help inform future conservation actions or mitigation efforts.
Ecological generalism and behavioural innovation in birds: technical intelligence or the simple incorporation of new foods?
1. Generalist species are more successful than specialists in anthropogenically modified environments or in environments in which they have been introduced, but the nature of the link between generalism and establishment success is unclear. 2. A higher feeding innovation rate has previously been reported in habitat generalist birds from North America. By allowing them to exploit new resources, this higher feeding innovation rate might explain the generalists' advantage. This result might be due to generalists being more likely to find new resources because they are exposed to more diverse environmental conditions. Alternatively, they might differ from specialists in other traits, in particular cognitive skills that might allow them to innovate more complex food searching and handling techniques. 3. To test these hypotheses, we separated avian feeding innovations into a 'technical' (novel searching and handling behaviour) and a 'food type' (incorporation of a new food in a species' diet) category. Technical innovations, but not food type innovations, have previously been shown to correlate with avian brain size, suggesting they reflect cognitive ability. We used a world-wide data base of 2339 feeding innovations recorded in the literature, covering a total of 765 avian species and assessed the correlations between brain size and feeding innovation rates on one side and habitat and diet generalism on the other. 4. Habitat generalism was positively related with food type innovation rate, but not technical innovation rate or brain size. This suggests that habitat generalist species are more likely to incorporate new food types in their diet because of higher chances to find new food resources in their environment, or of a higher opportunism, but not enhanced cognitive skills. In contrast, diet generalist species had higher food type and technical innovation rates, as well as larger brains, suggesting that cognitive skills might help species expand their diet breadth or that an increase in diet breadth might favour the evolution of enhanced cognitive abilities. 5. Our results provide new insights into the nature of the generalists' advantage in the face of environmental changes, and suggest that dietary and habitat generalism are different, but convergent, routes to feeding flexibility and adaptation to changed environments.
Feeding ecology of the sympatric waterbirds in Neotropical floodplain
Understanding the trophic interactions and coexistence processes among waterbirds in floodplain ecosystems is of fundamental ecological importance. In the upper Paraná River floodplain, we assessed the diet of five sympatric waterbird species (Ardea alba, Ardea cocoi, Egretta thula, Nannopterum brasilianum, and Nycticorax nycticorax) and tested their differences in the diet, in addition to food overlap, differences in trophic niche breadths and stratum in the water column where they forage. The waterbirds’ stomachs were collected quarterly on the upper Paraná River floodplain, analyzed under a stereomicroscope, and the food items were identified. Only Egretta thula was classified as omnivorous, consuming various food resources, including insects, decapods, and fish. The other species were piscivorous, but differed in the types of prey. Food overlap was higher in the piscivorous species, but they exhibited high trophic niche breadth. The piscivorous waterbirds employ different strategies for exploiting food resources that allow species coexistence in the floodplain, avoiding direct competition. Our results highlight the importance of waterbirds as connectors across diverse environments, especially aquatic-terrestrial ecosystems. Since these waterbirds’ diet relies on fish, effective conservation and management strategies targeting fish communities are fundamental to maintaining biodiversity and functionality within the upper Paraná River floodplain.
Superiority of native soil core microbiomes in supporting plant growth
Native core microbiomes represent a unique opportunity to support food provision and plant-based industries. Yet, these microbiomes are often neglected when developing synthetic communities (SynComs) to support plant health and growth. Here, we study the contribution of native core, native non-core and non-native microorganisms to support plant production. We construct four alternative SynComs based on the excellent growth promoting ability of individual stain and paired non-antagonistic action. One of microbiome based SynCom (SC2) shows a high niche breadth and low average variation degree in-vitro interaction. The promoting-growth effect of SC2 can be transferred to non-sterile environment, attributing to the colonization of native core microorganisms and the improvement of rhizosphere promoting-growth function including nitrogen fixation, IAA production, and dissolved phosphorus. Further, microbial fertilizer based on SC2 and composite carrier (rapeseed cake fertilizer + rice husk carbon) increase the net biomass of plant by 129%. Our results highlight the fundamental importance of native core microorganisms to boost plant production. Native core microbiomes are often neglected when developing synthetic microbial communities to support plant health and growth. Here, the authors show that native core microorganisms have greater potential to support plant growth than both native non-core and non-native microorganisms.
Surprisingly wide climatic niche breadth of a relict mountain species raises hope for survival under climate change
Aims We assessed the juvenile climatic niche breadth of a relict mountain species by comparing field observations and transplant experiments within and beyond the elevational limits of its distribution range. Location Lebanon – Near East – Mediterranean region. Methods We studied the survival and growth of the Cedar of Lebanon ( Cedrus libani ) to determine the lower and upper elevational range limits of its juvenile stage through an experimental setup with and without water supplementation and with potentially competing species as a control. The experiment included eight common gardens at elevations ranging from 110 to 2330 m, within and far beyond the warm and cold limits of Cedar distribution observed under natural conditions. Results We observed unexpectedly high survival and growth rates of Cedar at elevations well below the range of its natural distribution in Lebanon. Below the observed warm limit, water stress at very low elevations and competition at low and medium elevations limited juvenile survival. In contrast, cold temperature and water stress limited survival at elevations slightly above the observed upper natural limit. The experimental setup demonstrated that the elevation range suitable for Cedar growth and survival was twice as wide as the range within which Cedar is observed under natural conditions. Main Conclusions High survival rates experimentally observed beyond the warm limit of the natural distribution range of the Cedar of Lebanon raise hope for its resilience to ongoing climate warming. If this pattern were frequent among montane species, it would challenge predictions of massive extinction with climate change and pave the way for promoting adaptive actions such as competition management to improve their survival.