53 resultados para benthic ecology


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The dominance of ''ecosystem services'' as a guiding concept for environmental management - where it appears as a neutral, obvious, taken-for-granted concept - hides the fact that there are choices implicit in its framing and in its application. In other words, it is a highly political concept, and its utility depends on the arena in which it is used and what it is used for. Following a political ecology framework, and based on a literature review, bibliometric analyses, and brief examples from two tropical rainforest countries, this review investigates four moments in the construction and application of the ecosystem services idea: socio-historical (the emergence of the discourse), ontological (what knowledge does the concept allow?), scientific (difficulties in its practical application), and political (who wins, who loses?). We show how the concept is a boundary object with widespread appeal, trace the discursive and institutional context within which it gained traction, and argue that choices of scale, definition, and method in measuring ecosystem services frustrate its straightforward application. As a result, it is used in diverse ways by dif- ferent interests to justify different kinds of interventions that at times might be totally opposed. In Madagascar, the ecosystem services idea is mainly used to justify forest conservation in ways open to cri- tique for its neoliberalization of nature or disempowerment of communities. In contrast, in the Brazilian Amazon, the discourse of ecosystem services has served the agendas of traditional populations and family farm lobbies. Ecosystem services, as an idea and tool, are mobilized by diverse actors in real-life situa- tions that lead to complex, regionally particular and fundamentally political outcomes.

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The global human population is expected to reach ∼9 billion by 2050. Feeding this many people represents a major challenge requiring global crop yield increases of up to 100%. Microbial symbionts of plants such as arbuscular mycorrhizal fungi (AMF) represent a huge, but unrealized resource for improving yields of globally important crops, especially in the tropics. We argue that the application of AMF in agriculture is too simplistic and ignores basic ecological principals. To achieve this challenge, a community and population ecology approach can contribute greatly. First, ecologists could significantly improve our understanding of the determinants of the survival of introduced AMF, the role of adaptability and intraspecific diversity of AMF and whether inoculation has a direct or indirect effect on plant production. Second, we call for extensive metagenomics as well as population genomics studies that are crucial to assess the environmental impact that introduction of non-local AMF may have on native AMF communities and populations. Finally, we plead for an ecologically sound use of AMF in efforts to increase food security at a global scale in a sustainable manner.

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How do plants that move and spread across landscapes become branded as weeds and thereby objects of contention and control? We outline a political ecology approach that builds on a Lefebvrian understanding of the production of space, identifying three scalar moments that make plants into 'weeds' in different spatial contexts and landscapes. The three moments are: the operational scale, which relates to empirical phenomena in nature and society; the observational scale, which defines formal concepts of these phenomena and their implicit or explicit 'biopower' across institutional and spatial categories; and the interpretive scale, which is communicated through stories and actions expressing human feelings or concerns regarding the phenomena and processes of socio-spatial change. Together, these three scalar moments interact to produce a political ecology of landscape transformation, where biophysical and socio-cultural processes of daily life encounter formal categories and modes of control as well as emotive and normative expectations in shaping landscapes. Using three exemplar 'weeds' - acacia, lantana and ambrosia - our political ecology approach to landscape transformations shows that weeds do not act alone and that invasives are not inherently bad organisms. Humans and weeds go together; plants take advantage of spaces and opportunities that we create. Human desires for preserving certain social values in landscapes in contradiction to actual transformations is often at the heart of definitions of and conflicts over weeds or invasives.

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Neutral and selective processes c an drive repeated patterns of evolu tion in dif ferent groups of populationsexp eriencing similar ecol ogica l gradients. In this paper, we used a combinat ion of nucl ear and mitochondrialDNA markers, as well as geometric morphometrics, to investigate repeated patterns of morphological andgenetic divergence of E uropean minnows in two mountain ranges : the Pyrenees and the Al ps. Europeanminnows (Phoxinus phoxinus) are cyprinid fish i nha bitin g most freshwater bodies in Europe, including those indifferent mountain r anges that could act as major geographical barriers to gene flow. We explored patterns ofP. phoxinus phenotypic and genetic di versi fication along a gradi ent of alti tude common to the two mountainranges, and tested for isolation by distance (IBD), isolation by environment (IBE) and isolation by adaptation(IBA). The results indicated that populations from the Pyr enees a nd the Alps bel ong to two well differentiated,reciprocally monophyletic mt DNA lineages. Substantial genetic differentiation due to geographical isolationwithin and between populations from the Pyrenees and the Alps was also found using rapidly evolving AFLPsmarkers (isolation by distance or IBD), as well as morphological differences between mountain ranges. Als o,morphology varied strong ly with elevation and so did genetic differentiation to a lower extent. Despitemoderate evidence for IBE and IBA, and therefore of repeated evolution, substantial population heterogeneitywas found at the genetic level, suggesting that selection and population specific genetic drift act in concert toaffect genetic divergence.

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BACKGROUND: The structure and organisation of ecological interactions within an ecosystem is modified by the evolution and coevolution of the individual species it contains. Understanding how historical conditions have shaped this architecture is vital for understanding system responses to change at scales from the microbial upwards. However, in the absence of a group selection process, the collective behaviours and ecosystem functions exhibited by the whole community cannot be organised or adapted in a Darwinian sense. A long-standing open question thus persists: Are there alternative organising principles that enable us to understand and predict how the coevolution of the component species creates and maintains complex collective behaviours exhibited by the ecosystem as a whole? RESULTS: Here we answer this question by incorporating principles from connectionist learning, a previously unrelated discipline already using well-developed theories on how emergent behaviours arise in simple networks. Specifically, we show conditions where natural selection on ecological interactions is functionally equivalent to a simple type of connectionist learning, 'unsupervised learning', well-known in neural-network models of cognitive systems to produce many non-trivial collective behaviours. Accordingly, we find that a community can self-organise in a well-defined and non-trivial sense without selection at the community level; its organisation can be conditioned by past experience in the same sense as connectionist learning models habituate to stimuli. This conditioning drives the community to form a distributed ecological memory of multiple past states, causing the community to: a) converge to these states from any random initial composition; b) accurately restore historical compositions from small fragments; c) recover a state composition following disturbance; and d) to correctly classify ambiguous initial compositions according to their similarity to learned compositions. We examine how the formation of alternative stable states alters the community's response to changing environmental forcing, and we identify conditions under which the ecosystem exhibits hysteresis with potential for catastrophic regime shifts. CONCLUSIONS: This work highlights the potential of connectionist theory to expand our understanding of evo-eco dynamics and collective ecological behaviours. Within this framework we find that, despite not being a Darwinian unit, ecological communities can behave like connectionist learning systems, creating internal conditions that habituate to past environmental conditions and actively recalling those conditions. REVIEWERS: This article was reviewed by Prof. Ricard V Solé, Universitat Pompeu Fabra, Barcelona and Prof. Rob Knight, University of Colorado, Boulder.

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Carbon dioxide emissions from anthropic activities have accumulated in the atmosphere in excess of 800 Gigatons since preindustrial times, and are continuously increasing. Among other strategies, CO2 capture and storage is one option to mitigate the emissions from large point sources. In addition, carbon dioxide extraction from ambient air is assessed to reduce the atmospheric concentration of CO2. Both direct and indirect (through photosynthesis) pathways are possible. Geological sequestration has significant disadvantages (high cost, low public acceptance, long term uncertainty) whereas carbon dioxide recycling (or utilization) is more consistent with the basic principle of industrial ecology, almost closing material cycles. In this article, a series of technologies for CO2 capture and valorization is described as integrated and optimized pathways. This integration increases the environmental and economic benefits of each technology. Depending on the source of carbon dioxide, appropriate capture and valorization processes are evaluated based on material and energy constraints.

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Free-living amoebae are distributed worldwide and are frequently in contact with humans and animals. As cysts, they can survive in very harsh conditions and resist biocides and most disinfection procedures. Several microorganisms, called amoeba-resisting microorganisms (ARMs), have evolved to survive and multiply within these protozoa. Among them are many important pathogens, such as Legionella and Mycobacteria, and also several newly discovered Chlamydia-related bacteria, such as Parachlamydia acanthamoebae, Estrella lausannensis, Simkania negevensis or Waddlia chondrophila whose pathogenic role towards human or animal is strongly suspected. Amoebae represent an evolutionary crib for their resistant microorganisms since they can exchange genetic material with other ARMs and develop virulence traits that will be further used to infect other professional phagocytes. Moreover, amoebae constitute an ideal tool to isolate strict intracellular microorganisms from complex microbiota, since they will feed on other fast-growing bacteria, such as coliforms potentially present in the investigated samples. The paradigm that ARMs are likely resistant to macrophages, another phagocytic cell, and that they are likely virulent towards humans and animals is only partially true. Indeed, we provide examples of the Chlamydiales order that challenge this assumption and suggest that the ability to multiply in protozoa does not strictly correlate with pathogenicity and that we should rather use the ability to replicate in multiple and diverse eukaryotic cells as an indirect marker of virulence towards mammals. Thus, cell-culture-based microbial culturomics should be used in the future to try to discover new pathogenic bacterial species.