The tendency for more closely related species to share similar traits and ecological strategies can be explained by their longer shared evolutionary histories and represents phylogenetic conservatism. How strongly species traits co-vary with phylogeny can significantly impact how we analyze cross-species data and can influence our interpretation of assembly rules in the rapidly expanding field of community phylogenetics. Phylogenetic conservatism is typically quantified by analyzing the distribution of species values on the phylogenetic tree that connects them. Many phylogenetic approaches, however, assume a completely sampled phylogeny: while we have good estimates of deeper phylogenetic relationships for many species-rich groups, such as birds and flowering plants, we often lack information on more recent interspecific relationships (i.e., within a genus). A common solution has been to represent these relationships as polytomies on trees using taxonomy as a guide. Here we show that such trees can dramatically inflate estimates of phylogenetic conservatism quantified using S. P. Blomberg et al.'s K statistic. Using simulations, we show that even randomly generated traits can appear to be phylogenetically conserved on poorly resolved trees. We provide a simple rarefaction-based solution that can reliably retrieve unbiased estimates of K, and we illustrate our method using data on first flowering times from Thoreau's woods (Concord, Massachusetts, USA). 相似文献
The spatial scale of similarity among fish communities is characteristically large in temperate marine systems: connectivity is enhanced by high rates of dispersal during the larval/juvenile stages and the increased mobility of large-bodied fish. A larger spatial scale of similarity (low beta diversity) is advantageous in heavily exploited systems because locally depleted populations are more likely to be "rescued" by neighboring areas. We explored whether the spatial scale of similarity changed from 1970 to 2006 due to overfishing of dominant, large-bodied groundfish across a 300 000-km2 region of the Northwest Atlantic. Annually, similarities among communities decayed slowly with increasing geographic distance in this open system, but through time the decorrelation distance declined by 33%, concomitant with widespread reductions in biomass, body size, and community evenness. The decline in connectivity stemmed from an erosion of community similarity among local subregions separated by distances as small as 100 km. Larger fish, of the same species, contribute proportionally more viable offspring, so observed body size reductions will have affected maternal output. The cumulative effect of nonlinear maternal influences on egg/larval quality may have compromised the spatial scale of effective larval dispersal, which may account for the delayed recovery of certain member species. Our study adds strong support for using the spatial scale of similarity as an indicator of metacommunity stability both to understand the spatial impacts of exploitation and to refine how spatial structure is used in management plans. 相似文献
IntroductionWe investigated falls at a metropolitan airport to determine fall incidence, identify potential causes of these falls, and suggest opportunities for mitigation.MethodsWe used deidentified incident reports of all falls requiring EMS response that occurred at the airport during 2009 and 2010.ResultsOn average, one fall occurred every 2.3 days. Ninety-six percent (96%) of falls occurred in terminals. Of all falls, 44% occurred on escalators, making escalators the most common location. Seventy-two percent (72%) of fallers were females; 43% were ≥ 65 years; 92% of all falls resulted in a documented injury; 37% of falls resulted in transport to hospital emergency departments. Escalator fall risks include carrying bags (due to changes in baggage fees), using cells phones, not using handrails, and compromised strength and balance.Conclusions and ImpactDiverting at-risk passengers to elevators could significantly reduce the overall falls. Interventions targeting escalator falls have the greatest promise for reducing falls at this airport. 相似文献
This paper explores the crucial part that faith‐based organisations (FBOs) play in acting as intermediaries between international donors and local faith communities (LFCs) implementing humanitarian relief projects for Syrian refugees. Humanitarian responses to the mounting Syrian refugee crisis have coincided with greater collaboration between international donors and LFCs. This cooperation often is facilitated by a complex web of non‐state intermediaries at the international, national, and local level. This study probes the breadth of roles of these intermediaries, drawing on primary data from case studies of two Christian intermediaries supporting Christian LFCs as they deliver aid primarily to Muslim Syrian refugees in Jordan and Lebanon. The results of the study are connected to the wider literature on LFCs in humanitarian response, revealing how intermediaries address issues of accountability, capacity‐building, impartiality, neutrality, and professionalism. The paper concludes by offering suggestions for further research on intermediaries as key actors in the localisation of humanitarian assistance. 相似文献
Contamination of coastal water is a persistent threat to ecosystems around the world. In this study, a novel model for describing the dispersion, dilution, terminal layer formation and influence area from a point source discharge into a water body is presented and compared with field measured data. The model is a Combined Integral and Particle model (CIPMO). In the initial stage, the motion, dispersion and dilution of a buoyant jet are calculated. The output from the buoyant jet model is then coupled with a Lagrangian Advection and Diffusion model describing the far-field. CIPMO ensures that both the near- and far-field processes are adequately resolved. The model either uses empirical data or collects environmental forcing data from open source hydrodynamic models with high spatial and temporal resolution. The method for coupling the near-field buoyant jet and the particle tracking model is described and the output is discussed. The model shows good results when compared with measurements from a field study.
Environmental Geochemistry and Health - Biochar (BC) is a porous, carbonaceous material produced by slow pyrolysis of biomass under oxygen-limited conditions. BC production has been attracting... 相似文献
There is a paucity of research on the subjective stress‐related experiences of humanitarian aid workers. Most evaluations of stress among these individuals focus on trauma and related conditions or adopt a quantitative approach. This interview‐based study explored how 58 humanitarian aid workers employed by a United Nations‐aligned organisation perceived the transactional stress process. The thematic analysis revealed eight main topics of interest: an emergency culture was found where most employees felt compelled to offer an immediate response to humanitarian needs; employees identified strongly with humanitarian goals and reported a high level of engagement; the rewards of humanitarian work were perceived as motivating and meaningful; constant change and urgent demands resulted in work overload; and managing work–life boundaries and receiving positive support from colleagues and managers helped to buffer perceived stress, work overload, and negative health outcomes. The practical implications of the results are discussed and suggestions made in the light of current research and stress theory. 相似文献
Pyrogenic plants dominate many fire-prone ecosystems. Their prevalence suggests some advantage to their enhanced flammability, but researchers have had difficulty tying pyrogenicity to individual-level advantages. Based on our review, we propose that enhanced flammability in fire-prone ecosystems should protect the belowground organs and nearby propagules of certain individual plants during fires. We base this hypothesis on five points: (1) organs and propagules by which many fire-adapted plants survive fires are vulnerable to elevated soil temperatures during fires; (2) the degree to which burning plant fuels heat the soil depends mainly on residence times of fires and on fuel location relative to the soil; (3) fires and fire effects are locally heterogeneous, meaning that individual plants can affect local soil heating via their fuels; (4) how a plant burns can thus affect its fitness; and (5) in many cases, natural selection in fire-prone habitats should therefore favor plants that burn rapidly and retain fuels off the ground. We predict an advantage of enhanced flammability for plants whose fuels influence local fire characteristics and whose regenerative tissues or propagules are affected by local variation in fires. Our "pyrogenicity as protection" hypothesis has the potential to apply to a range of life histories. We discuss implications for ecological and evolutionary theory and suggest considerations for testing the hypothesis. 相似文献
Even though “sustainable development” seems to have emerged as the development paradigm of the 1990s, a great deal of vagueness
still surrounds the meaning, definition, and theoretical underpinnings of the concept. There is also a general lack of emphasis
on the spatial dimension of sustainable development when developing relevant conceptual or environmental accounting frameworks.
In clarifying the concept, this article proposes a definition that explicitly incorporates the temporal as well as the spatial
dimension of sustainability. It also develops a logically consistent conceptual framework for the analysis and evaluation
of sustainable development, following a spatial systems approach. Five interconnected aspatial subsystems or subsets of a
spatial system are identified and their respective operational dimensions discussed. A proposed composite index calleddegree of stainable development (DSD) and its five component indicators are also outlined. The difficulties involved in operationalizing the DSD measure
and the conceptual framework are noted, and the various tasks that need to be undertaken in this regard are specified. It
is concluded that future research utilizing the proposed conceptual framework should not only foster the development of appropriate
methodologies for the comparative evaluation of sustainable development at global, national, or regional scales, but also
offer insights to appropriate decision makers at various levels regarding available options and alternative actions for the
healthy development of their respective societies. 相似文献