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1.
Ecol Lett ; 27(4): e14411, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38577993

RESUMO

Intensified agriculture, a driver of biodiversity loss, can diminish ecosystem functions and their stability. Biodiversity can increase functional redundancy and is expected to stabilize ecosystem functions. Few studies, however, have explored how agricultural intensity affects functional redundancy and its link with ecosystem function stability. Here, within a continental-wide study, we assess how functional redundancy of seed predation is affected by agricultural intensity and landscape simplification. By combining carabid abundances with molecular gut content data, functional redundancy of seed predation was quantified for 65 weed genera across 60 fields in four European countries. Across weed genera, functional redundancy was reduced with high field management intensity and simplified crop rotations. Moreover, functional redundancy increased the spatial stability of weed seed predation at the field scale. We found that ecosystem functions are vulnerable to disturbances in intensively managed agroecosystems, providing empirical evidence of the importance of biodiversity for stable ecosystem functions across space.


Assuntos
Ecossistema , Comportamento Predatório , Animais , Biodiversidade , Sementes , Agricultura
2.
Agron Sustain Dev ; 42(3): 53, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35702339

RESUMO

A profound transformation of agricultural production methods has become unavoidable due to the increase in the world's population, and environmental and climatic challenges. Agroecology is now recognized as a challenging model for agricultural systems, promoting their diversification and adaptation to environmental and socio-economic contexts, with consequences for the entire agri-food system and the development of rural and urban areas. Through a prospective exercise performed at a large interdisciplinary institute, INRAE, a research agenda for agroecology was built that filled a gap through its ambition and interdisciplinarity. It concerned six topics. For genetics, there is a need to study genetic aspects of complex systems (e.g., mixtures of genotypes) and to develop breeding methods for them. For landscapes, challenges lie in effects of heterogeneity at multiple scales, in multifunctionality and in the design of agroecological landscapes. Agricultural equipment and digital technologies show high potential for monitoring dynamics of agroecosystems. For modeling, challenges include approaches to complexity, consideration of spatial and temporal dimensions and representation of the cascade from cropping practices to ecosystem services. The agroecological transition of farms calls for modeling and observational approaches as well as for creating new design methods. Integration of agroecology into food systems raises the issues of product specificity, consumer behavior and organization of markets, standards and public policies. In addition, transversal priorities were identified: (i) generating sets of biological data, through research and participatory mechanisms, that are appropriate for designing agroecological systems and (ii) collecting and using coherent sets of data to enable assessment of vulnerability, resilience and risk in order to evaluate the performance of agroecological systems and to contribute to scaling up. The main lessons learned from this collective exercise can be useful for the entire scientific community engaged in research into agroecology.

3.
Environ Monit Assess ; 193(Suppl 1): 75, 2021 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-33988768

RESUMO

Over the last decades, land management options have been investigated that aim at enhancing services to agriculture delivered by biodiversity and its associated biotic interactions. Such services can be promoted through land management strategies ranging from in-field single agricultural practices, long-term strategies compiling these agricultural practices at the crop rotation scale, to management strategies at the landscape scale. In this paper, we provide an overview of the land management options that can be implemented at multiple scales, with a specific focus on the provision of one service that is key in agriculture, i.e. pest control. We present existing knowledge and highlight current gaps and limitations in our understanding of pest control response to land management. Based on this analysis, we propose two promising and complementary research approaches that could help filling existing knowledge gaps and provide guidelines for designing landscapes for agroecological services: (1) landscape monitoring networks (LMN), based on long-term monitoring of ecological and managerial processes within sets of landscapes located in contrasted production contexts; (2) agroecological system experiments (ASE), which design and assess combinations of land management options at multiple embedded spatial scales.


Assuntos
Monitoramento Ambiental , Controle Biológico de Vetores , Agricultura , Biodiversidade , Ecossistema
4.
Environ Manage ; 56(5): 1078-90, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26071767

RESUMO

Amongst the biodiversity components of agriculture, weeds are an interesting model for exploring management options relying on the principle of ecological intensification in arable farming. Weeds can cause severe crop yield losses, contribute to farmland functional biodiversity and are strongly associated with the generic issue of pesticide use. In this paper, we address the impacts of herbicide reduction following a causal framework starting with herbicide reduction and triggering changes in (i) the management options required to control weeds, (ii) the weed communities and functions they provide and (iii) the overall performance and sustainability of the implemented land management options. The three components of this framework were analysed in a multidisciplinary project that was conducted on 55 experimental and farmer's fields that included conventional, integrated and organic cropping systems. Our results indicate that the reduction of herbicide use is not antagonistic with crop production, provided that alternative practices are put into place. Herbicide reduction and associated land management modified the composition of in-field weed communities and thus the functions of weeds related to biodiversity and production. Through a long-term simulation of weed communities based on alternative (?) cropping systems, some specific management pathways were identified that delivered high biodiversity gains and limited the negative impacts of weeds on crop production. Finally, the multi-criteria assessment of the environmental, economic and societal sustainability of the 55 systems suggests that integrated weed management systems fared better than their conventional and organic counterparts. These outcomes suggest that sustainable management could possibly be achieved through changes in weed management, along a pathway starting with herbicide reduction.


Assuntos
Agricultura/métodos , Biodiversidade , Herbicidas , Controle de Plantas Daninhas/métodos , Conservação dos Recursos Naturais , Produtos Agrícolas , Ecologia , Plantas Daninhas/fisiologia
5.
Sci Total Environ ; 916: 170182, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38244626

RESUMO

Reducing pesticide use while maintaining agricultural production is a key challenge. Ecological theory predicts that landscape simplification is likely to increase insect pest outbreaks and limit their control by natural enemies, and this situation could boost insecticide use. Some studies have indeed detected that simpler landscapes were associated with higher insecticide use, but very few have demonstrated that this association is caused by landscape effects on pest abundance. Here, we analysed insecticide use and pest pressure in response to landscape simplification across 557 arable farms across France. Accounting for potentially confounding covariates, we found that lower cover of hedgerows in the landscape, but not semi natural areas, were associated with higher on-farm insecticide use. We also found that greater hedgerow coverage was associated with lower aphid pest pressure. Specifically, increasing the landscape-scale cover of hedgerows from 1 % to 3 % meant that insecticide use was halved. These findings suggest that restoring hedgerow cover at the landscape scale should be targeted in order to speed-up the ecological intensification of agriculture.


Assuntos
Inseticidas , Praguicidas , Animais , Ecossistema , Agricultura , Fazendas , Controle Biológico de Vetores
6.
Weed Res ; 63(1): 1-11, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-37082111

RESUMO

Over the last 30 years, many studies have surveyed weed vegetation on arable land. The 'Arable Weeds and Management in Europe' (AWME) database is a collection of 36 of these surveys and the associated management data. Here, we review the challenges associated with combining disparate datasets and explore some of the opportunities for future research that present themselves thanks to the AWME database. We present three case studies repeating previously published national scale analyses with data from a larger spatial extent. The case studies, originally done in France, Germany and the UK, explore various aspects of weed ecology (community composition, management and environmental effects and within-field distributions) and use a range of statistical techniques (canonical correspondence analysis, redundancy analysis and generalised linear mixed models) to demonstrate the utility and versatility of the AWME database. We demonstrate that (i) the standardisation of abundance data to a common measure, before the analysis of the combined dataset, has little impact on the outcome of the analyses, (ii) the increased extent of environmental or management gradients allows for greater confidence in conclusions and (iii) the main conclusions of analyses done at different spatial scales remain consistent. These case studies demonstrate the utility of a Europe-wide weed survey database, for clarifying or extending results obtained from studies at smaller scales. This Europe-wide data collection offers many more opportunities for analysis that could not be addressed in smaller datasets; including questions about the effects of climate change, macro-ecological and biogeographical issues related to weed diversity as well as the dominance or rarity of specific weeds in Europe.

7.
J Neurooncol ; 109(1): 167-75, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22660920

RESUMO

Purpose of this study was to determine the effect of waiting time for radiotherapy on overall survival of patients with glioblastoma treated in the EORTC-NCIC trial at 18 centers in France. A total of 400 adult patients with glioblastoma who were treated between January 1, 2006 and December 31, 2006 were included. There were 282 patients with "minimum criteria" according to the EORTC-NCIC trial: (i) concurrent chemotherapy with temozolomide; and (ii) age between 18 and 70 years old. Among these patients, 229 were treated with adjuvant temozolomide and were classified as "maximal criteria". One-hundred and eighteen patients were in the "without minimal criteria" group. Waiting time from the first symptom (FS-RT), pathology diagnosis (P-RT), multidisciplinary meeting (MM-RT), surgery (S-RT), and CT scan for delineation (CT-RT) until the start of radiotherapy were recorded. Median follow-up for all patients was 327 days. Overall, median FS-RT, P-RT, MM-RT, CT-RT, and S-RT times were 77, 36, 32, 12, and 41 days, respectively. Median, and 12 and 24-month overall survival were 409 days, and 56.3 ± 2.1 % and 27.6 ± 2.6 %, respectively. Univariate analysis failed to reveal a difference in survival, irrespective of the delay. In multivariate analysis, independent favorable prognostic factors for overall survival were age (p ≤ 0.0001) and type of surgery (p = 0.0006). In this large series treated during the EORTC-NCIC protocol period, waiting time until radiotherapy did not seem to affect patient outcome.


Assuntos
Neoplasias Encefálicas/terapia , Quimiorradioterapia , Dacarbazina/análogos & derivados , Glioblastoma/terapia , Listas de Espera , Adulto , Idoso , Idoso de 80 Anos ou mais , Antineoplásicos Alquilantes/uso terapêutico , Neoplasias Encefálicas/mortalidade , Quimioterapia Adjuvante , Dacarbazina/uso terapêutico , Feminino , Seguimentos , França , Glioblastoma/mortalidade , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Dosagem Radioterapêutica , Estudos Retrospectivos , Taxa de Sobrevida , Temozolomida , Fatores de Tempo
8.
J Anim Ecol ; 81(1): 4-13, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21883203

RESUMO

1. There is an urgent need to accurately model how environmental change affects the wide-scale functioning of ecosystems, but advances are hindered by a lack of knowledge of how trophic levels are linked across space. It is unclear which theoretical approach to take to improve modelling of such interactions, but evidence is gathering that linking species responses to their functional traits can increase understanding of ecosystem dynamics. Currently, there are no quantitative studies testing how this approach might improve models of multiple, trophically interacting species, at wide spatial scales. 2. Arable weeds play a foundational role in linking food webs, providing resources for many taxa, including carabid beetles that feed on their seeds and weed-associated invertebrate prey. Here, we model associations between weeds and carabids across farmland in Great Britain (GB), to test the hypothesis that wide-scale trophic links between these groups are structured by their species functional traits. 3. A network of c. 250 arable fields, covering four crops and most lowland areas of GB, was sampled for weed, carabid and invertebrate taxa over 3 years. Data sets of these groups were closely matched in time and space, and each contained numerous species with a range of eco-physiological traits. The consistency of trophic linkages between multiple taxa sharing functional traits was tested within multivariate and log-linear models. 4. Robust links were established between the functional traits of taxa and their trophic interactions. Autumn-germinating, small-seeded weeds were associated with smaller, spring-breeding carabids, more specialised in seed feeding, whereas spring-germinating, large-seeded weeds were associated with a range of larger, autumn-breeding omnivorous carabids. These relationships were strong and dynamic, being independent of changes in invertebrate food resources and consistent across sample dates, crops and regions of GB. 5. We conclude that, in at least one system of interacting taxa, functional traits can be used to predict consistent, wide-scale trophic links. This conceptual approach is useful for assessing how perturbations affecting lower trophic levels are ramified throughout ecosystems and could be used to assess how environmental change affects a wider range of secondary consumers.


Assuntos
Biota , Besouros/fisiologia , Produtos Agrícolas/fisiologia , Cadeia Alimentar , Plantas Daninhas/fisiologia , Animais , Preferências Alimentares , Invertebrados/fisiologia , Modelos Biológicos , Plantas Daninhas/anatomia & histologia , Dinâmica Populacional , Reprodução , Estações do Ano , Sementes/anatomia & histologia , Sementes/fisiologia , Especificidade da Espécie , Reino Unido
9.
Commun Biol ; 4(1): 75, 2021 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-33462363

RESUMO

Agriculture is under pressure to achieve sustainable development goals for biodiversity and ecosystem services. Services in agro-ecosystems are typically driven by key species, and changes in the community composition and species abundance can have multifaceted effects. Assessment of individual services overlooks co-variance between different, but related, services coupled by a common group of species. This partial view ignores how effects propagate through an ecosystem. We conduct an analysis of 374 agricultural multilayer networks of two related services of weed seed regulation and gastropod mollusc predation delivered by carabid beetles. We found that weed seed regulation increased with the herbivore predation interaction frequency, computed from the network of trophic links between carabids and weed seeds in the herbivore layer. Weed seed regulation and herbivore interaction frequencies declined as the interaction frequencies between carabids and molluscs in the carnivore layer increased. This suggests that carabids can switch to gastropod predation with community change, and that link turnover rewires the herbivore and carnivore network layers affecting seed regulation. Our study reveals that ecosystem services are governed by ecological plasticity in structurally complex, multi-layer networks. Sustainable management therefore needs to go beyond the autecological approaches to ecosystem services that predominate, particularly in agriculture.


Assuntos
Besouros , Ecossistema , Gastrópodes , Controle Biológico de Vetores , Controle de Plantas Daninhas , Animais , Herbivoria , Comportamento Predatório , Sementes , Reino Unido
10.
J Neurooncol ; 97(2): 195-205, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19768659

RESUMO

The objective of the present study was to investigate the interest of convection-enhanced delivery (CED) for the administration of a nanocarrier-based radiosensitizing chemotherapy in the rat brain. Pursuing on newly developed lipid nanocapsules (LNC) that can be internalised within brain tumour cells, we studied their intracerebral distribution when labelled with fluorescent Nile red (NR). As paclitaxel (Px) represents an interesting radiosensitiser, we also evaluated the potential radiosensitising effects of Px-loaded LNC administered through CED in the 9L intracranial rat glioblastoma model. The distribution study demonstrated that CED injection of NR-loaded LNC (NR-LNC) improved significantly the volume of distribution of NR when matched with simple injection (by about 150 fold). It also reveals that the LNC perfusion of a whole tumour forming area inside the CNS (6 days after implantation of 10(3) 9L cells) is achievable through CED injection, whilst preserving the ability of LNC to reach the intracellular space of encountered tumour cells. Having established an animal model of encephalic irradiation close to the clinic (18 Gray in three fractions of six Gray at days 8, 11 and 14 after 9L cell implantation) we proved the feasibility of the combination of CED for the administration of drug-loaded LNC with external beam therapy. Although a single CED injection of Px-LNC at low Px dose (375 mug/kg of bodyweight) gave the best median survival (twice that of untreated controls), it underlines the need for optimisation. Hence, the possibility of grafting recognition moieties onto the LNC surface combined to their biocompatibility must be beneficial.


Assuntos
Neoplasias Encefálicas/terapia , Convecção , Glioblastoma/terapia , Nanocápsulas , Paclitaxel/administração & dosagem , Radiossensibilizantes/administração & dosagem , Animais , Separação Celular , Terapia Combinada , Feminino , Citometria de Fluxo , Microscopia Confocal , Nanocápsulas/química , Nanotecnologia/métodos , Ratos , Ratos Endogâmicos F344
11.
Pharm Res ; 27(1): 56-64, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19908129

RESUMO

PURPOSE: The goal of the present study was to evaluate the efficacy of a new organometallic drug, ferrociphenol (Fc-diOH), in combination with external radiotherapy in intracerebral 9L glioma model. We tested the hypothesis that the combination of external radiotherapy with Fc-diOH could potentiate the action of this drug. METHODS: 9L cells were treated with Fc-diOH-LNCs (from 0.01 to 1 micromol/L) and irradiated with external radiotherapy (from 2 to 40 Gy). In vivo assessment was evaluated by the inoculation of 9L cells in Fisher rats. Chemotherapy with Fc-diOH-LNCs (0.36 mg/rat) was administered by means of convection-enhanced delivery (CED), and the treatment was followed by three irradiations of 6 Gy doses (total dose = 18 Gy). RESULTS: In vitro evaluations evidenced that a combined treatment with Fc-diOH-LNCs and irradiations showed synergistic antitumor activity on 9L cells. Combining cerebral irradiation with CED of Fc-diOH-LNCs led to a significantly longer survival and the existence of long-term survivors compared to Fc-diOH-LNCs-treated animals (p < 0.0001) and to the group treated with blank LNCs + radiotherapy (p = 0.0079). CONCLUSION: The synergistic effect between ferrociphenol-loaded LNCs and radiotherapy was due to a closely oxidative relationship. Upon these considerations, Fc-diOH-LNCs appear to be an efficient radiosensitive anticancer drug delivery system.


Assuntos
Antineoplásicos/uso terapêutico , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/radioterapia , Irradiação Craniana/métodos , Compostos Ferrosos/uso terapêutico , Nanocápsulas/uso terapêutico , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/química , Neoplasias Encefálicas/mortalidade , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Terapia Combinada/métodos , Feminino , Compostos Ferrosos/administração & dosagem , Compostos Ferrosos/química , Glioma/tratamento farmacológico , Glioma/mortalidade , Glioma/radioterapia , Infusões Intralesionais , Nanocápsulas/administração & dosagem , Nanocápsulas/química , Ratos , Ratos Endogâmicos F344 , Ensaios Antitumorais Modelo de Xenoenxerto
12.
BMC Ecol ; 10: 20, 2010 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-20809982

RESUMO

BACKGROUND: Theory in ecology points out the potential link between the degree of specialisation of organisms and their responses to disturbances and suggests that this could be a key element for understanding the assembly of communities. We evaluated this question for the arable weed flora as this group has scarcely been the focus of ecological studies so far and because weeds are restricted to habitats characterised by very high degrees of disturbance. As such, weeds offer a case study to ask how specialization relates to abundance and distribution of species in relation to the varying disturbance regimes occurring in arable crops. RESULTS: We used data derived from an extensive national monitoring network of approximately 700 arable fields scattered across France to quantify the degree of specialisation of 152 weed species using six different ecological methods. We then explored the impact of the level of disturbance occurring in arable fields by comparing the degree of specialisation of weed communities in contrasting field situations.The classification of species as specialist or generalist was consistent between different ecological indices. When applied on a large-scale data set across France, this classification highlighted that monoculture harbour significantly more specialists than crop rotations, suggesting that crop rotation increases abundance of generalist species rather than sets of species that are each specialised to the individual crop types grown in the rotation. Applied to a diachronic dataset, the classification also shows that the proportion of specialist weed species has significantly decreased in cultivated fields over the last 30 years which suggests a biotic homogenization of agricultural landscapes. CONCLUSIONS: This study shows that the concept of generalist/specialist species is particularly relevant to understand the effect of anthropogenic disturbances on the evolution of plant community composition and that ecological theories developed in stable environments are valid in highly disturbed environments such as agro-ecosystems. The approach developed here to classify arable weeds according to the breadth of their ecological niche is robust and applicable to a wide range of organisms. It is also sensitive to disturbance regime and we show here that recent changes in agricultural practices, i.e. increased levels of disturbance have favoured the most generalist species, hence leading to biotic homogenisation in arable landscapes.


Assuntos
Agricultura/métodos , Biota , Plantas Daninhas/classificação , Produtos Agrícolas/crescimento & desenvolvimento , Ecologia/métodos , França , Herbicidas
13.
Plants (Basel) ; 9(6)2020 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-32580354

RESUMO

Arable field margins are valuable habitats providing a wide range of ecosystem services in rural landscapes. Agricultural intensification in recent decades has been a major cause of decline in plant diversity in these habitats. However, the concomitant effects on plant functional diversity are less documented, particularly in Mediterranean areas. In this paper, we analyzed the effect of margin width and surrounding landscape (cover and diversity of land use and field size), used as proxies for management intensity at local and landscape scales, on plant species richness, functional diversity and functional trait values in margins of winter cereal fields in southern Spain. Five functional traits were selected: life form, growth form, seed mass, seed dispersal mode and pollination type. RLQ and fourth-corner analyses were used to link functional traits and landscape variables. A total of 306 plant species were recorded. Species richness and functional diversity were positively related to margin width but showed no response to landscape variables. Functional trait values were affected neither by the local nor landscape variables. Our results suggest that increasing the margin width of conventionally managed cereal fields would enhance both taxonomic and functional diversity of margin plant assemblages, and thus the services they provide to the agro-ecosystem.

14.
Sci Rep ; 10(1): 19315, 2020 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-33168869

RESUMO

Carabids are generalist predators that contribute to the agricultural ecosystem service of seedbank regulation via weed seed predation. To facilitate adoption of this ecosystem services by farmers, knowledge of weed seed predation and the resilience of seedbank regulation with co-varying availability of alternative prey is crucial. Using assessments of the seedbank and predation on seed cards in 57 cereal fields across Europe, we demonstrate a regulatory effect on the soil seedbank, at a continental scale, by groups formed of omnivore, seed-eating (granivore + omnivore) and all species of carabids just prior to the crop-harvest. Regulation was associated with a positive relationship between the activity-density of carabids and seed predation, as measured on seed cards. We found that per capita seed consumption on the cards co-varied negatively with the biomass of alternative prey, i.e. Aphididae, Collembola and total alternative prey biomass. Our results underline the importance of weed seedbank regulation by carabids, across geographically significant scales, and indicate that the effectiveness of this biocontrol may depend on the availability of alternative prey that disrupt the weed seed predation.


Assuntos
Agricultura/métodos , Besouros/fisiologia , Ecossistema , Plantas Daninhas/fisiologia , Sementes/fisiologia , Animais , Biomassa , Ecologia , Grão Comestível , Europa (Continente) , Hordeum , Modelos Lineares , Comportamento Predatório , Triticum
15.
J Environ Manage ; 90(9): 2851-6, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-18835081

RESUMO

Rural landscapes are highly dynamic and their change impacts on a number of ecological processes such as the dynamics of biodiversity. Although a substantial amount of research has focused on quantifying these changes and their impact on biodiversity, most studies have focused on single dimensions of land use change. This lack of integration in land use change studies can be explained by the fact that data on the spatial, temporal, and ecological dimensions of land use are seldom available for the same geographical location. In this paper, the benefits of taking into account these three dimensions are illustrated with results derived from the Great Britain Countryside Surveys (CS), a large-scale monitoring programme designed to assess change in the extent and ecological condition of British habitats. The overview of CS results presented in this paper shows that (1) changes in land use composition will translate into a variety of spatial patterns; (2) the temporal stability of land use is often lower than can be expected; and (3) there can be large-scale shifts in the ecological condition of the land use types that form our rural landscapes. The benefits of integrated rural landscape studies are discussed in the context of other national monitoring programmes.


Assuntos
Biodiversidade , Meio Ambiente , Planejamento Social , Agricultura , Coleta de Dados , Ecologia/métodos , Monitoramento Ambiental , Geografia/métodos , Reino Unido
16.
PLoS One ; 12(11): e0187167, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29121652

RESUMO

Animals foraging in the wild have to balance speed of decision making and accuracy of assessment of a food item's quality. If resource quality is important for maximizing fitness, then the duration of decision making may be in conflict with other crucial and time consuming tasks, such as anti-predator behaviours or competition monitoring. Individuals facing the risk of predation and/or competition should adjust the duration of decision making and, as a consequence, their level of choosiness for resources. When exposed to predation, the forager could either maintain its level of choosiness for food items but accept a reduction in the amount of food items consumed or it could reduce its level of choosiness and accept all prey items encountered. Under competition risk, individuals are expected to reduce their level of choosiness as slow decision making exposes individuals to a higher risk of opportunity costs. To test these predictions, the level of choosiness of a seed-eating carabid beetle, Harpalus affinis, was examined under 4 different experimental conditions of risk: i) predation risk; ii) intraspecific competition; iii) interspecific competition; and, iv) control. All the risks were simulated using chemical cues from individual conspecifics or beetles of different species that are predatory or granivorous. Our results show that when foraging under the risk of predation, H. affinis individuals significantly reduce their level of choosiness for seeds. Reductions in level of choosiness for food items might serve as a sensible strategy to reduce both the total duration of a foraging task and the cognitive load of the food quality assessment. No significant differences were observed when individuals were exposed to competition cues. Competition, (i.e opportunity cost) may not be perceived as risk high enough to induce changes in the level of choosiness. Our results suggest that considering the amount of items consumed, alone, would be a misleading metric when assessing individual response to a risk of predation. Foraging studies should therefore also take in account the decision making process.


Assuntos
Comportamento de Escolha , Preferências Alimentares , Alimentos , Comportamento Predatório/fisiologia , Animais , Estimativa de Kaplan-Meier , Movimento , Risco , Sementes
17.
Ambio ; 35(6): 297-303, 2006 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17240762

RESUMO

Intensification of farming practices is still a major driver of biodiversity loss in Europe, despite the implementation of policies that aim to reverse this trend. A conceptual framework called MIRABEL was previously developed that enabled a qualitative and expert-based assessment of the impact of agricultural intensification on ecologically valuable habitats. We present a quantitative update of the previous assessment that uses newly available pan-European spatially explicit data on pressures and habitats at risk. This quantitative assessment shows that the number of calcareous grasslands potentially at risk of eutrophication and overgrazing is rapidly increasing in Europe. Decreases in nitrogen surpluses and stocking densities that occurred between 1990 and 2000 have rarely led to values that were below the ecological thresholds. At the same time, a substantial proportion of calcareous grassland that has so far experienced low values for indicators of farming intensification has faced increases between 1990 and 2000 and could well become at high risk from farming intensification in the near future. As such, this assessment is an early warning signal, especially for habitats located in areas that have traditionally been farmed extensively. When comparing the outcome of this assessment with the previous qualitative MIRABEL assessment, it appears that if pan-European data are useful to assess the intensity of the pressures, more work is needed to identify regional variations in the response of biodiversity to such pressures. This is where a qualitative approach based on regional expertise should be used to complement data-driven assessments.


Assuntos
Agricultura , Monitoramento Ambiental , Eutrofização , Agricultura/tendências , Biodiversidade , Ecossistema , Europa (Continente) , Estudos de Avaliação como Assunto , Humanos , Modelos Teóricos , Medição de Risco
18.
Presse Med ; 34(7): 506-8, 2005 Apr 09.
Artigo em Francês | MEDLINE | ID: mdl-15903003

RESUMO

INTRODUCTION: Pulmonary complications of radiotherapy are rare, but bronchiolitis obliterans organizing pneumonia (BOOP) is observed in 2.5% of cases. It can develop after radiation treatment of breast cancer as well as, more rarely, lung cancer, sarcoma, Hodgkin's disease or malignant thymoma. CASE: Ten months after radiotherapy for breast cancer, a 52 year-old woman developed migratory alveolar opacities outside the radiation field. Their improvement with corticosteroid treatment led to the diagnosis of BOOP. DISCUSSION: BOOP, which resembles infectious pneumonia, can develop 2-7 months after the end of radiotherapy and is seen especially in women aged 50-60 years with fever and coughs resistant to antibiotics. Dyspnea is far rarer. Imaging reveals patchy infiltrates with widespread bilateral, mobile lesions extended over and above the radiation field. Biopsy is required to confirm diagnosis; sections, which may or may not come from the radiation field, reveal the nonspecific granulomatous alveolar infiltrates typical of BOOP. Other causes should be eliminated (toxic, immune, iatrogenic or even idiopathic infection and recurrent early neoplastic relapse). Association with hormone therapy does not influence the course of BOOP. Outcome with corticosteroid treatment is excellent.


Assuntos
Neoplasias da Mama/radioterapia , Pneumonia em Organização Criptogênica/etiologia , Lesões por Radiação , Corticosteroides/uso terapêutico , Tosse/etiologia , Pneumonia em Organização Criptogênica/tratamento farmacológico , Feminino , Febre/etiologia , Humanos , Pessoa de Meia-Idade
19.
C R Biol ; 326 Suppl 1: S200-9, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14558470

RESUMO

Comparison of dispersal rates of the bog fritillary butterfly between continuous and fragmented landscapes indicates that between patch dispersal is significantly lower in the fragmented landscape, while population densities are of the same order of magnitude. Analyses of the dynamics of the suitable habitat for the butterfly in the fragmented landscape reveal a severe, non linear increase in spatial isolation of patches over a time period of 30 years (i.e. 30 butterfly generations), but simulations of the butterfly metapopulation dynamics using a structured population model show that the lower dispersal rates in the fragmented landscape are far above the critical threshold leading to metapopulation extinction. These results indicate that changes in individual behaviour leading to the decrease of dispersal rates in the fragmented landscape were rapidly selected for when patch spatial isolation increased. The evidence of such an adaptive answer to habitat fragmentation suggests that dispersal mortality is a key factor for metapopulation persistence in fragmented landscapes. We emphasise that landscape spatial configuration and patch isolation have to be taken into account in the debate about large-scale conservation strategies.


Assuntos
Borboletas , Meio Ambiente , Animais , Bélgica , Conservação dos Recursos Naturais/métodos , Modelos Biológicos , Plantas/classificação , Densidade Demográfica
20.
PLoS One ; 9(6): e97922, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24887494

RESUMO

Reducing pesticide use is one of the high-priority targets in the quest for a sustainable agriculture. Until now, most studies dealing with pesticide use reduction have compared a limited number of experimental prototypes. Here we assessed the sustainability of 48 arable cropping systems from two major agricultural regions of France, including conventional, integrated and organic systems, with a wide range of pesticide use intensities and management (crop rotation, soil tillage, cultivars, fertilization, etc.). We assessed cropping system sustainability using a set of economic, environmental and social indicators. We failed to detect any positive correlation between pesticide use intensity and both productivity (when organic farms were excluded) and profitability. In addition, there was no relationship between pesticide use and workload. We found that crop rotation diversity was higher in cropping systems with low pesticide use, which would support the important role of crop rotation diversity in integrated and organic strategies. In comparison to conventional systems, integrated strategies showed a decrease in the use of both pesticides and nitrogen fertilizers, they consumed less energy and were frequently more energy efficient. Integrated systems therefore appeared as the best compromise in sustainability trade-offs. Our results could be used to re-design current cropping systems, by promoting diversified crop rotations and the combination of a wide range of available techniques contributing to pest management.


Assuntos
Agricultura/economia , Agricultura/métodos , Conservação dos Recursos Naturais/economia , Meio Ambiente , Praguicidas/análise , Produtos Agrícolas/economia , Produtos Agrícolas/crescimento & desenvolvimento
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