Laboratoire Chrono-Environnement

The ESC Guidelines represent the views of the ESC and were arrived at after careful consideration of the available evidence at the time they were written. Health professionals are encouraged to take them fully into account when exercising their clinical judgement. The guidelines do not, however, override the individual responsibility of health professionals to make appropriate decisions in the circumstances of the individual patients, in consultation with that patient, and where appropriate and necessary the patient's guardian or carer. It is also the health professional's responsibility to verify the rules and regulations applicable to drugs and devices at the time of prescription.

Over the past decade, a significant increase in the circulation of infectious agents was observed. With the spread and emergence of epizootics, zoonoses and epidemics, the risks of pandemics became more and more critical. Human and animal health has also been threatened by antimicrobial resistance, environmental pollution and the development of multifactorial and chronic diseases. This highlighted the increasing globalization of health risks and the importance of the human-animal-ecosystem interface in the evolution and emergence of pathogens. A better knowledge of causes and consequences of certain human activities, lifestyles and behaviors in ecosystems is crucial for a rigorous interpretation of disease dynamics and to drive public policies. As a global good, health security must be understood on a global scale and from a global and cross-cutting perspective, integrating human health, animal health, plant health, ecosystems health and biodiversity. In this paper, we discuss how crucial it is to consider ecological, evolutionary and environmental sciences in understanding the emergence and re-emergence of infectious diseases and in facing the challenges of antimicrobial resistance. We also discuss the application of the “One Health” concept to non-communicable chronic diseases linked to exposure to multiple stresses, including toxic stress, and new lifestyles. Finally, we draw up a list of barriers that need removing and the ambitions that we must nurture for the effective application of the “One Health” concept. We conclude that the success of this One Health concept now requires breaking down the interdisciplinary barriers that still separate human and veterinary medicine from ecological, evolutionary and environmental sciences. The development of integrative approaches should be promoted by linking the study of factors underlying stress responses to their consequences on ecosystem functioning and evolution. This knowledge is required for the development of novel control strategies inspired by environmental mechanisms leading to desired equilibrium and dynamics in healthy ecosystems and must provide in the near future a framework for more integrated operational initiatives.

The allohexaploid bread wheat genome consists of three closely related subgenomes (A, B, and D), but a clear understanding of their phylogenetic history has been lacking. We used genome assemblies of bread wheat and five diploid relatives to analyze genome-wide samples of gene trees, as well as to estimate evolutionary relatedness and divergence times. We show that the A and B genomes diverged from a common ancestor ~7 million years ago and that these genomes gave rise to the D genome through homoploid hybrid speciation 1 to 2 million years later. Our findings imply that the present-day bread wheat genome is a product of multiple rounds of hybrid speciation (homoploid and polyploid) and lay the foundation for a new framework for understanding the wheat genome as a multilevel phylogenetic mosaic.

Subfossil pollen and plant macrofossil data derived from 14C-dated sediment profiles can provide quantitative information on glacial and interglacial climates. The data allow climate variables related to growing-season warmth, winter cold, and plant-available moisture to be reconstructed. Continental-scale reconstructions have been made for the mid-Holocene (MH, around 6 ka) and Last Glacial Maximum (LGM, around 21 ka), allowing comparison with palaeoclimate simulations currently being carried out as part of the fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. The synthesis of the available MH and LGM climate reconstructions and their uncertainties, obtained using modern-analogue, regression and model-inversion techniques, is presented for four temperature variables and two moisture variables. Reconstructions of the same variables based on surface-pollen assemblages are shown to be accurate and unbiased. Reconstructed LGM and MH climate anomaly patterns are coherent, consistent between variables, and robust with respect to the choice of technique. They support a conceptual model of the controls of Late Quaternary climate change whereby the first-order effects of orbital variations and greenhouse forcing on the seasonal cycle of temperature are predictably modified by responses of the atmospheric circulation and surface energy balance.

Background: To correlate the appearance of Alveolar Echinococcosis (AE) hepatic lesions in Magnetic Resonance Imaging (MRI) as defined by Kodama, to the metabolic activity visualized in 18-Fluoro-DeoxyGlucose Positron Emission Tomography combined with Computed Tomography (PET/CT). Methods: Forty-two patients (25 men; mean age: 62.2) diagnosed with AE and who underwent both MRI and PET/CT were included. Three independent readers blinded with regard to the PET/CT information, divided the forty-two hepatic lesions into five types according to Kodama's classification. Concerning PET/CT, two independent readers, unaware of the MRI information, considered the results as positive when an increased FDG-uptake was observed at 1 or 3 hours after FDG injection, and as negative when no increased uptake was noted. Inter-observer agreement was assessed by using j statistics. Results: Forty-two lesions were counted and the mean diameter of overall evaluated lesions was 6.3 cm. One lesion (2.4%) was categorized as type 1, 11 (26.2%) as type 2, 24 (57.1%) as type 3, 3 (7.1%) as type 4 and 3 (7.1%) as type 5. The inter-observer analysis found a j coefficient of 0.96. All type-1, 90.9% of type-2 and 87.5% of type-3 lesions showed an increased FDG-uptake on PET/CT images. All non-microcystic AE liver lesions (types 4, 5) showed no abnormal increased FDG uptake on PET/CT images. The inter-observer analysis at one and three hours found a j coefficient of: 0.95 and 0.92, respectively. Conclusion: In patients with AE liver lesions, the absence of micro-cysts on MRI is strongly correlated to a metabolically inactive disease.

BACKGROUND: Observational studies showed that the profile of infective endocarditis (IE) significantly changed over the past decades. However, most studies involved referral centers. We conducted a population-based study to control for this referral bias. The objective was to update the description of characteristics of IE in France and to compare the profile of community-acquired versus healthcare-associated IE. METHODS: A prospective population-based observational study conducted in all medical facilities from 7 French regions (32% of French individuals aged ≥18 years) identified 497 adults with Duke-Li-definite IE who were first admitted to the hospital in 2008. Main measures included age-standardized and sex-standardized incidence of IE and multivariate Cox regression analysis for risk factors of in-hospital death. RESULTS: The age-standardized and sex-standardized annual incidence of IE was 33.8 (95% confidence interval [CI], 30.8-36.9) cases per million inhabitants. The incidence was highest in men aged 75-79 years. A majority of patients had no previously known heart disease. Staphylococci were the most common causal agents, accounting for 36.2% of cases (Staphylococcus aureus, 26.6%; coagulase-negative staphylococci, 9.7%). Healthcare-associated IE represented 26.7% of all cases and exhibited a clinical pattern significantly different from that of community-acquired IE. S. aureus as the causal agent of IE was the most important factor associated with in-hospital death in community-acquired IE (hazard ratio [HR], 2.82 [95% CI, 1.72-4.61]) and the single factor in healthcare-associated IE (HR, 2.54 [95% CI, 1.33-4.85]). CONCLUSIONS: S. aureus became both the leading cause and the most important prognostic factor of IE, and healthcare-associated IE appeared as a major subgroup of the disease.

On the basis of glacier and lake-level records, this paper attempts, for the first time, a comparison between high-resolution palaeohydrological and palaeoglaciological data in west-central Europe over the past 3500 years. A data set of tree-ring width, radiocarbon and archaeological data, in addition to historical sources, were used to reconstruct fluctuations of the Great Aletsch, the Gorner and the Lower Grindelwald glaciers in the Swiss Alps. The three ice-streams experienced nearly synchronous advances at c. 1000-600 BC and AD 500-600, 800-900, 1100-1200 and 1300-1860. These glacier fluctuations show strong correspondence with lake-level variations reconstructed in eastern France (Jura mountains and Pre-Alps) and on the Swiss Plateau. This supports the hypothesis of climatically driven fluctuations. Historical data available for the period since AD 1550 reveal, in detail, various meteorological conditions behind the successive glacier advances. However, in agreement with the general trend shown by the historical data, the synchroneity between glacier advances and periods of higher lake level suggests the impact of general winter cooling and an increase in summer moisture as responsible for reinforced feeding of both glaciers and lakes in west-central Europe over the past 3500 years. Finally, a comparison between the Great Aletsch glacier and the residual 14 C records supports the hypothesis that variations in solar activity were a major forcing factor of climatic oscillations in west-central Europe during the late Holocene.

Technical developments in molecular biology have found extensive applications in the field of microbial ecology. Among these techniques, fingerprinting methods such as denaturing gel electrophoresis (DGE, including the three options: DGGE, TGGE and TTGE) has been applied to environmental samples over this last decade. Microbial ecologists took advantage of this technique, originally developed for the detection of single mutations, for the analysis of whole bacterial communities. However, until recently, the results of these high quality fingerprinting patterns were restricted to a visual interpretation, neglecting the analytical potential of the method in terms of statistical significance and ecological interpretation. A brief recall is presented here about the principles and limitations of DGE fingerprinting analysis, with an emphasis on the need of standardization of the whole analytical process. The main content focuses on statistical strategies for analysing the gel patterns, from single band examination to the analysis of whole fingerprinting profiles. Applying statistical method make the DGE fingerprinting technique a promising tool. Numerous samples can be analysed simultaneously, permitting the monitoring of microbial communities or simply bacterial groups for which occurrence and relative frequency are affected by any environmental parameter. As previously applied in the fields of plant and animal ecology, the use of statistics provides a significant advantage for the non-ambiguous interpretation of the spatial and temporal functioning of microbial communities.

BACKGROUND: Dietary changes are suggested to play a role in the increasing prevalence of allergic diseases and asthma. Short-chain fatty acids (SCFAs) are metabolites present in certain foods and are produced by microbes in the gut following fermentation of fibers. SCFAs have been shown to have anti-inflammatory properties in animal models. Our objective was to investigate the potential role of SCFAs in the prevention of allergy and asthma. METHODS: We analyzed SCFA levels by high-performance liquid chromatography (HPLC) in fecal samples from 301 one-year-old children from a birth cohort and examined their association with early life exposures, especially diet, and allergy and asthma later in life. Data on exposures and allergic diseases were collected by questionnaires. In addition, we treated mice with SCFAs to examine their effect on allergic airway inflammation. RESULTS: Significant associations between the levels of SCFAs and the infant's diet were identified. Children with the highest levels of butyrate and propionate (≥95th percentile) in feces at the age of one year had significantly less atopic sensitization and were less likely to have asthma between 3 and 6 years. Children with the highest levels of butyrate were also less likely to have a reported diagnosis of food allergy or allergic rhinitis. Oral administration of SCFAs to mice significantly reduced the severity of allergic airway inflammation. CONCLUSION: Our results suggest that strategies to increase SCFA levels could be a new dietary preventive option for allergic diseases in children.

We constructed an 800,000-year synthetic record of Greenland climate variability based on the thermal bipolar seesaw model. Our Greenland analog reproduces much of the variability seen in the Greenland ice cores over the past 100,000 years. The synthetic record shows strong similarity with the absolutely dated speleothem record from China, allowing us to place ice core records within an absolute timeframe for the past 400,000 years. Hence, it provides both a stratigraphic reference and a conceptual basis for assessing the long-term evolution of millennial-scale variability and its potential role in climate change at longer time scales. Indeed, we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the Middle to Late Pleistocene.

The conventional waste management practices dispose or incinerate agricultural and forestry waste, contributing to the environmental pollution while misusing biomass, a valuable resource with a great potential of reuse. In fact, cultivation of agricultural crops and harvesting generate an abundant amount of waste (e.g., stones, shells, straw) that can be used for wastewater treatment. Waste biomass may be used as: (i) an adsorbent in its original, raw form, following ambient drying and grinding; (ii) modified bio-based sorbents; or (iii) a source material for the synthesis of activated carbon adsorbents through carbonization. Despite the numerous publications in this field examining the removal of a wide range of target pollutants (metals, metalloids, dyes, pesticides, as well as emerging contaminants) by several materials, more realistic studies are still required to evaluate the potential to remove residual compounds in complex matrices, by testing natural matrices, i.e., environmental samples without spiking the target compounds. This perspective paper highlights how an integrated-engineering approach may help solving environmental-pollution issues related to water, solid waste, and air pollution. Chiefly, the application of locally produced bio-waste as an adsorbent for wastewater treatment tackles water contamination, decreases the overall amount of agricultural waste, and reduces the potential gas emissions caused by waste transportation, treatment and/or disposal.

Summary Trait‐based approaches are increasingly being used to test mechanisms underlying species assemblages and biotic interactions across a wide range of organisms including terrestrial arthropods and to investigate consequences for ecosystem processes. Such an approach relies on the standardized measurement of functional traits that can be applied across taxa and regions. Currently, however, unified methods of trait measurements are lacking for terrestrial arthropods and related macroinvertebrates (terrestrial invertebrates hereafter). Here, we present a comprehensive review and detailed protocol for a set of 29 traits known to be sensitive to global stressors and to affect ecosystem processes and services. We give recommendations how to measure these traits under standardized conditions across various terrestrial invertebrate taxonomic groups. We provide considerations and approaches that apply to almost all traits described, such as the selection of species and individuals needed for the measurements, the importance of intraspecific trait variability, how many populations or communities to sample and over which spatial scales. The approaches outlined here provide a means to improve the reliability and predictive power of functional traits to explain community assembly, species diversity patterns and ecosystem processes and services within and across taxa and trophic levels, allowing comparison of studies and running meta‐analyses across regions and ecosystems. This handbook is a crucial first step towards standardizing trait methodology across the most studied terrestrial invertebrate groups, and the protocols are aimed to balance general applicability and requirements for special cases or particular taxa. Therefore, we envision this handbook as a common platform to which researchers can further provide methodological input for additional special cases. A lay summary is available for this article.

Abstract Part of the missing sink in the global CO 2 budget has been attributed to the positive effects of CO 2 fertilization and N deposition on carbon sequestration in Northern Hemisphere terrestrial ecosystems. The genus Sphagnum is one of the most important groups of plant species sequestrating carbon in temperate and northern bog ecosystems, because of the low decomposability of the dead material it produces. The effects of raised CO 2 and increased atmospheric N deposition on growth of Sphagnum and other plants were studied in bogs at four sites across Western Europe. Contrary to expectations, elevated CO 2 did not significantly affect Sphagnum biomass growth. Increased N deposition reduced Sphagnum mass growth, because it increased the cover of vascular plants and the tall moss Polytrichum strictum . Such changes in plant species composition may decrease carbon sequestration in Sphagnum ‐dominated bog ecosystems.

Importance: Atopic dermatitis is an inflammatory, pruritic skin disease that often occurs in early infancy with a chronic course. However, a specific description of subtypes of atopic dermatitis depending on the timing of onset and progression of the disease in childhood is lacking. Objective: To identify different phenotypes of atopic dermatitis using a definition based on symptoms before age 6 years and to determine whether some subtypes are more at risk for developing other allergic diseases. Design, Setting, and Participants: The Protection Against Allergy Study in Rural Environments (PASTURE) is a European birth cohort where pregnant women were recruited between August 2002 and March 2005 and divided in 2 groups dependent on whether they lived on a farm. Children from this cohort with data on atopic dermatitis from birth to 6 years of age were included. Exposures: Atopic dermatitis, defined as an itchy rash on typical locations from birth to 6 years. Main Outcomes and Measures: The latent class analysis was used to identify subtypes of atopic dermatitis in childhood based on the course of symptoms. Multivariable logistic regressions were used to analyze the association between atopic dermatitis phenotypes and other allergic diseases. Results: We included 1038 children; of these, 506 were girls. The latent class analysis model with the best fit to PASTURE data separated 4 phenotypes of atopic dermatitis in childhood: 2 early phenotypes with onset before age 2 years (early transient [n = 96; 9.2%] and early persistent [n = 67; 6.5%]), the late phenotype with onset at age 2 years or older (n = 50; 4.8%), and the never/infrequent phenotype (n = 825; 79.5%), defined as children with no atopic dermatitis. Children with both parents with history of allergies were 5 times more at risk to develop atopic dermatitis with an early-persistent phenotype compared with children with parents with no history of allergies. Both early phenotypes were strongly associated with food allergy. The risk of developing asthma was significantly increased among the early-persistent phenotype (adjusted odds ratio, 2.87; 95% CI, 1.31-6.31). The late phenotype was only positively associated with allergic rhinitis. Conclusions and Relevance: Using latent class analysis, 4 phenotypes of atopic dermatitis were identified depending on the onset and course of the disease. The prevalence of asthma and food allergy by 6 years of age was strongly increased among children with early phenotypes (within age 2 years), especially with persistent symptoms. These findings are important for the development of strategies in allergy prevention.

Abstract. On the basis of a multi-proxy approach and a strategy combining lacustrine and marine records along a north–south transect, data collected in the central Mediterranean within the framework of a collaborative project have led to reconstruction of high-resolution and well-dated palaeohydrological records and to assessment of their spatial and temporal coherency. Contrasting patterns of palaeohydrological changes have been evidenced in the central Mediterranean: south (north) of around 40° N of latitude, the middle part of the Holocene was characterised by lake-level maxima (minima), during an interval dated to ca. 10 300–4500 cal BP to the south and 9000–4500 cal BP to the north. Available data suggest that these contrasting palaeohydrological patterns operated throughout the Holocene, both on millennial and centennial scales. Regarding precipitation seasonality, maximum humidity in the central Mediterranean during the middle part of the Holocene was characterised by humid winters and dry summers north of ca. 40° N, and humid winters and summers south of ca. 40° N. This may explain an apparent conflict between palaeoclimatic records depending on the proxies used for reconstruction as well as the synchronous expansion of tree species taxa with contrasting climatic requirements. In addition, south of ca. 40° N, the first millennium of the Holocene was characterised by very dry climatic conditions not only in the eastern, but also in the central- and the western Mediterranean zones as reflected by low lake levels and delayed reforestation. These results suggest that, in addition to the influence of the Nile discharge reinforced by the African monsoon, the deposition of Sapropel 1 has been favoured (1) by an increase in winter precipitation in the northern Mediterranean borderlands, and (2) by an increase in winter and summer precipitation in the southern Mediterranean area. The climate reversal following the Holocene climate optimum appears to have been punctuated by two major climate changes around 7500 and 4500 cal BP. In the central Mediterranean, the Holocene palaeohydrological changes developed in response to a combination of orbital, ice-sheet and solar forcing factors. The maximum humidity interval in the south-central Mediterranean started ca. 10 300 cal BP, in correlation with the decline (1) of the possible blocking effects of the North Atlantic anticyclone linked to maximum insolation, and/or (2) of the influence of the remnant ice sheets and fresh water forcing in the North Atlantic Ocean. In the north-central Mediterranean, the lake-level minimum interval began only around 9000 cal BP when the Fennoscandian ice sheet disappeared and a prevailing positive NAO-(North Atlantic Oscillation) type circulation developed in the North Atlantic area. The major palaeohydrological oscillation around 4500–4000 cal BP may be a non-linear response to the gradual decrease in insolation, with additional key seasonal and interhemispheric changes. On a centennial scale, the successive climatic events which punctuated the entire Holocene in the central Mediterranean coincided with cooling events associated with deglacial outbursts in the North Atlantic area and decreases in solar activity during the interval 11 700–7000 cal BP, and to a possible combination of NAO-type circulation and solar forcing since ca. 7000 cal BP onwards. Thus, regarding the centennial-scale climatic oscillations, the Mediterranean Basin appears to have been strongly linked to the North Atlantic area and affected by solar activity over the entire Holocene. In addition to model experiments, a better understanding of forcing factors and past atmospheric circulation patterns behind the Holocene palaeohydrological changes in the Mediterranean area will require further investigation to establish additional high-resolution and well-dated records in selected locations around the Mediterranean Basin and in adjacent regions. Special attention should be paid to greater precision in the reconstruction, on millennial and centennial timescales, of changes in the latitudinal location of the limit between the northern and southern palaeohydrological Mediterranean sectors, depending on (1) the intensity and/or characteristics of climatic periods/oscillations (e.g. Holocene thermal maximum versus Neoglacial, as well as, for instance, the 8.2 ka event versus the 4 ka event or the Little Ice Age); and (2) on varying geographical conditions from the western to the eastern Mediterranean areas (longitudinal gradients). Finally, on the basis of projects using strategically located study sites, there is a need to explore possible influences of other general atmospheric circulation patterns than NAO, such as the East Atlantic–West Russian or North Sea–Caspian patterns, in explaining the apparent complexity of palaeoclimatic (palaeohydrological) Holocene records from the Mediterranean area.

Core Ideas OZCAR is a network of sites studying the critical zone. OZCAR covers various disciplines. OZCAR will help disciplines to work together for a better representation and modeling of the critical zone. The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique–Application et Recherche or Critical Zone Observatories–Application and Research) is a National Research Infrastructure (RI). OZCAR‐RI is a network of instrumented sites, bringing together 21 pre‐existing research observatories monitoring different compartments of the zone situated between “the rock and the sky,” the Earth's skin or critical zone (CZ), over the long term. These observatories are regionally based and have specific initial scientific questions, monitoring strategies, databases, and modeling activities. The diversity of OZCAR‐RI observatories and sites is well representative of the heterogeneity of the CZ and of the scientific communities studying it. Despite this diversity, all OZCAR‐RI sites share a main overarching mandate, which is to monitor, understand, and predict (“earthcast”) the fluxes of water and matter of the Earth's near surface and how they will change in response to the “new climatic regime.” The vision for OZCAR strategic development aims at designing an open infrastructure, building a national CZ community able to share a systemic representation of the CZ, and educating a new generation of scientists more apt to tackle the wicked problem of the Anthropocene. OZCAR articulates around: (i) a set of common scientific questions and cross‐cutting scientific activities using the wealth of OZCAR‐RI observatories, (ii) an ambitious instrumental development program, and (iii) a better interaction between data and models to integrate the different time and spatial scales. Internationally, OZCAR‐RI aims at strengthening the CZ community by providing a model of organization for pre‐existing observatories and by offering CZ instrumented sites. OZCAR is one of two French mirrors of the European Strategy Forum on Research Infrastructure (eLTER‐ESFRI) project.

Abstract Palaeoenvironmental and archaeological data from Arbon Bleiche, Lake Constance (Switzerland) give evidence of a rapid rise in lake‐level dated by tree‐ring and radiocarbon to 5320 cal. yr BP. This rise event was the latest in a series of three successive episodes of higher lake‐level between 5550 and 5300 cal. yr BP coinciding with glacier advance and tree‐limit decline in the Alps. This west‐central European climate change may have favoured the quick burial and the preservation of the Alpine Iceman recently found in the Tyrolean Alps. It has possible equivalents in many records from various regions in both hemispheres dating to 5600–5000 cal. yr BP and corresponds to global cooling and contrasting patterns of hydrological changes. This major mid‐Holocene climate event marks the Hypsithermal/Neoglaciation transition possibly resulting from a combination of different factors including orbital forcing, changes in ocean circulation and variations in solar activity. Copyright © 2004 John Wiley & Sons, Ltd.

Abstract Modern humans have populated Europe for more than 45,000 years 1,2 . Our knowledge of the genetic relatedness and structure of ancient hunter-gatherers is however limited, owing to the scarceness and poor molecular preservation of human remains from that period 3 . Here we analyse 356 ancient hunter-gatherer genomes, including new genomic data for 116 individuals from 14 countries in western and central Eurasia, spanning between 35,000 and 5,000 years ago. We identify a genetic ancestry profile in individuals associated with Upper Palaeolithic Gravettian assemblages from western Europe that is distinct from contemporaneous groups related to this archaeological culture in central and southern Europe 4 , but resembles that of preceding individuals associated with the Aurignacian culture. This ancestry profile survived during the Last Glacial Maximum (25,000 to 19,000 years ago) in human populations from southwestern Europe associated with the Solutrean culture, and with the following Magdalenian culture that re-expanded northeastward after the Last Glacial Maximum. Conversely, we reveal a genetic turnover in southern Europe suggesting a local replacement of human groups around the time of the Last Glacial Maximum, accompanied by a north-to-south dispersal of populations associated with the Epigravettian culture. From at least 14,000 years ago, an ancestry related to this culture spread from the south across the rest of Europe, largely replacing the Magdalenian-associated gene pool. After a period of limited admixture that spanned the beginning of the Mesolithic, we find genetic interactions between western and eastern European hunter-gatherers, who were also characterized by marked differences in phenotypically relevant variants.

The loss of biodiversity has become a matter of urgent concern and a better understanding of local drivers is crucial for conservation. Although environmental heterogeneity is recognized as an important determinant of biodiversity, this has rarely been tested using field data at management scale. We propose and provide evidence for the simple hypothesis that local species diversity is related to spatial environmental heterogeneity. Species partition the environment into habitats. Biodiversity is therefore expected to be influenced by two aspects of spatial heterogeneity: 1) the variability of environmental conditions, which will affect the number of types of habitat, and 2) the spatial configuration of habitats, which will affect the rates of ecological processes, such as dispersal or competition. Earlier, simulation experiments predicted that both aspects of heterogeneity will influence plant species richness at a particular site. For the first time, these predictions were tested for plant communities using field data, which we collected in a wooded pasture in the Swiss Jura mountains using a four‐level hierarchical sampling design. Richness generally increased with increasing environmental variability and “roughness” (i.e. decreasing spatial aggregation). Effects occurred at all scales, but the nature of the effect changed with scale, suggesting a change in the underlying mechanisms, which will need to be taken into account if scaling up to larger landscapes. Although we found significant effects of environmental heterogeneity, other factors such as history could also be important determinants. If a relationship between environmental heterogeneity and species richness can be shown to be general, recently available high‐resolution environmental data can be used to complement the assessment of patterns of local richness and improve the prediction of the effects of land use change based on mean site conditions or land use history.

La mort cellulaire programmée (MCP) dans le règne végétal a été sujette à controverses pendant plusieurs années. Des évidences formelles ne permettent plus aujourd'hui de douter d'un tel phénomène dans le développement végétal ainsi que lors des réponses de défense des plantes envers les pathogènes. La comparaison de ce phénomène avec la mort cellulaire par apoptose des cellules animales semble montrer quelques troublantes analogies de mécanismes bien gue la MCP végétale se présente sous des morphologies bien différentes selon les cas. A l'horizon semble pourtant commencer à se profiler l'idée d'une MCP végétale dont le mécanisme non encore élucidé serait commun à tous les cas de développement et de réponses aux pathogènes mais dont la manifestation morphologique différerait pour répondre précisément aux besoins de la plante.