Ibanez S.,Swiss Federal Institute of forest |
Lavorel S.,CNRS Alpine Ecology Laboratory |
Puijalon S.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Moretti M.,Swiss Federal Institute of forest
Functional Ecology | Year: 2013
Despite their potential to provide a mechanistic understanding of ecosystem processes, the functional traits that govern interaction networks remain poorly understood. We investigated the extent to which biomechanical traits are related to consumption in a plant-grasshopper herbivory network. Using a choice experiment, we assessed the feeding patterns of 26 grasshopper species for 24 common plant species from subalpine grasslands. We quantified shear and punch toughness for each plant species, while grasshopper incisive and molar strengths were estimated by a lever mechanics model, following the measurement of mandibular traits. Models incorporating co-phylogenetic effects showed that the ratio between the grasshopper incisive strength and plant toughness, that reflects the cutting effort, is correlated with the mass of plant eaten. Moreover, a strong relationship between the incisive strength of the grasshoppers and the weighed mean toughness of the plants they eat was found. Our results suggest that biomechanical constraints imposed by plants influence the evolution of grasshoppers' mandibular traits. Such scaling relationships offer promising avenues towards the understanding of trait - function links in interaction networks. © 2013 British Ecological Society.
Lamouroux N.,IRSTEA |
Gore J.A.,The University of Tampa |
Lepori F.,University of Applied Sciences and Arts Southern Switzerland |
Statzner B.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Freshwater Biology | Year: 2015
Effective environmental management needs models that reliably predict quantitative ecological changes as a function of restoration effort (e.g. cost) and meet expectations of stakeholders. Principal threats to large rivers are linked to human-caused modifications of discharge and morphology of channels and floodplains. However, comprehensive large-scale tests of the reliability of models predicting ecological consequences of restoring these elements are still lacking. Following a governmental decision, water managers, local authorities and the 'Compagnie Nationale du Rhône' financed a scientific programme to develop, test and subsequently use predictive models to assess the restoration (particularly minimum flow increases and reconnections of floodplain channels with the main channel) of eight regulated reaches of the French Rhône River. This approach was fostered by (i) the existence of local initiatives aimed at the ecological improvement of the Rhône; (ii) a history of interactions based on trust among stakeholders; and (iii) knowledge provided by a large interdisciplinary research group that studied the Rhône for two decades before the programme started in 1998. This Special Issue synthesises the insights gained over recent decades of research during which four river reaches (total length 47 km) were restored since 1999. It contains 11 articles including this overview. One article relates physical habitats in the floodplain to river hydrology and morphology; five articles test predictive models linking changes in habitat conditions to changes in taxa abundance, community metrics and biological traits of macroinvertebrates and fish; and four articles address the effects of restoration in larger contexts (long-term community trends, optimisation of sampling strategies, social processes and bioindication). We describe the Rhône restoration project, explain the conceptual framework used to predict the effects of restoration on river biota and describe the contents of the Special Issue, the main results and their implications. The Rhône restoration led to more lotic and diverse aquatic communities and renewed social links with the river. When reliable pre-restoration data are available, simple habitat models can be used to predict quantitative ecological changes as a function of restoration effort. The project illustrates the need to describe changes in hydraulic conditions in studies of physical river restoration and shows the effort required for a powerful assessment of restoration effects. © 2015 John Wiley & Sons Ltd.
Lamouroux N.,IRSTEA |
Olivier J.-M.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Freshwater Biology | Year: 2015
Projects that restore river flows can be considered as in situ experiments and should be used to test predictions of the effects of flow changes on fish populations and communities. However, flow restoration projects often lack appropriate monitoring and replication. The Rhône restoration project has included repeated flow changes, in four bypassed reaches of the river, where the increase in minimum daily flow varied from minimal change to a tenfold increase. Fish communities (>55 000 individuals of 36 species) were electrofished at nine sites in the main channels of the four bypassed reaches, for 2-9 years before and for 5-10 years after the flow restoration. An instream hydraulic habitat model, published before restoration and based on observations of fish microhabitat preferences in independent reaches, was applied to the bypassed reaches to predict density changes for 14 species that accounted for 94% of the total fish abundance. In the two bypassed reaches where minimum flow was considerably increased (fivefold and tenfold), the abundance of species preferring fast-flowing and deep microhabitats increased by factors of 1.9 and 2.4, respectively, whereas the abundance of other species strongly decreased. Predicted changes in density made using the habitat model for these two reaches agreed with the observations at several sites and involved several fish species. In contrast, in the two bypassed reaches where flow changes were less, the observed changes in density were weak and less related to the model predictions. Hydraulic habitat models predicted changes of fish populations and the predictions also explained observed community responses to the changed flows. Ten years after the first flow restoration, our results suggest that the Rhône restoration generated perennial changes of the fish community structure, reversing community patterns that were observed prior to the flow restoration. © 2015 John Wiley & Sons Ltd.
Mermillod-Blondin F.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Lemoine D.G.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Functional Ecology | Year: 2010
Positive interactions driven by ecosystem engineers have been determined to be important community forces in stressed environments. By ameliorating habitat conditions, ecosystem engineering can create available ecological niches for other species. In poorly oxygenated sediments of freshwater wetlands, small invertebrates such as tubificid worms and chironomid larvae are known to function as active bioturbators; however, their effects on the growth and physiology of organisms which are constrained by low oxygenation of sediments have never been studied. We examined whether the common bioturbator, Tubifex tubifex, significantly influences the growth and the physiological state of two plant species, Elodea canadensis and Myriophyllum spicatum, in experimental systems simulating a water-sediment interface of wetlands. We also quantified the influence of plant-animal interactions on biogeochemical processes (fluxes of oxygen and nitrogen at the water-sediment interface) and microbial compartment in sediments. Tubificid worms stimulated growth of aboveground and belowground biomasses of the two plants through reduction in the anoxic stress in sediments. Myriophyllum spicatum, which was the best adapted to sedimentary anaerobic conditions, essentially increased its biomass whereas E. canadensis, less adapted to anaerobic conditions, shifted its root metabolism from anaerobic to aerobic. Biogeochemical processes were not significantly influenced by plant-animal interactions: (i) oxygen flux from overlying water to sediments probably reached a threshold that could not be raised by the increased plant biomass induced by worms and (ii) nitrogen fluxes were essentially linked to bioturbation activities of worms. Our study confirmed that the reduction in constraining variables by physical habitat modifications (ecosystem engineering) may play a crucial role in community and ecosystem processes. The fact that positive interactions measured between ecosystem engineers and plant species in anoxic wetland sediments were highly dependent on the ecophysiology of plant species suggests an extension of this first study to a wide range of macrophytes in order to determine the main plant functional traits driving plant-animal interactions in wetland sediments. © 2009 The Authors. Journal compilation © 2009 British Ecological Society.
Peru N.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Doledec S.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Ecological Indicators | Year: 2010
While compositional diversity is a common metric for assessing human impacts on aquatic communities, functional diversity is scarcely employed, though highly desirable from the perspective of the European Water Framework Directive. Using abundance data from 99 minimally disturbed sites (i.e., no or very weak anthropogenic impact) from a national survey, we studied the spatial variability of compositional and functional biodiversity metrics across a predefined ecoregional classification. Metrics of compositional diversity comprised taxonomic and EPT richness and Simpson diversity. Functional diversity metrics were based on Rao's Quadratic Entropy (RQE), which described the differences among benthic invertebrate genera in eleven biological traits (e.g., size, life cycle, reproduction types, feeding habits). Using generalized linear models we show that taxonomic richness may vary greatly across ecoregions, contrasting with Simpson diversity and functional metrics that varied weakly in response to natural environmental variability. Functional diversity metrics, because of their stability in response to natural environmental variability, may be useful tools for assessing human impairment to ecosystem function. We further tested the response of functional diversity metrics to a specific human impact (sewage) and demonstrated significant modifications of functional diversity downstream of sewage pollution. Further investigations are required to test the ability of functional diversity metrics to precisely and accurately indicate different types of human impacts. © 2010 Elsevier Ltd. All rights reserved.
Richardson C.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Lengagne T.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Proceedings of the Royal Society B: Biological Sciences | Year: 2010
Effective acoustic communication in the face of intense conspecific background noise constitutes a constant sensory challenge in chorusing and colonial species. An evolutionary approach suggests that behavioural and environmental constraints in these species should have shaped signal design and signalling behaviour to enable communication in noisy conditions. This could be attained both through the use of multicomponent signals and through short-term adjustments in the spatial separation of calling males. We investigated these two hypotheses in a chorusing anuran, the hylid Hyla arborea, through a series of phonotaxis experiments conducted within a six-speaker arena in a high background noise situation, by presenting females with male calls containing either single or multiple attractive call components, and by modifying distances between speakers. We found that female ability to discriminate attractive calls increased when several attractive call components were available, providing novel evidence that the use of multicomponent signals enhances communication in complex acoustic conditions. Signal discrimination in females also improved with speaker separation, demonstrating that within natural choruses, spatial unmasking conditioned by male density and spatial separation probably improves female discrimination of competing males. Implications of these results for the accuracy of mate choice within choruses are discussed. © 2009 The Royal Society.
Orias F.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Perrodin Y.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Science of the Total Environment | Year: 2013
The multiple activities that take place in hospitals (surgery, drug treatments, radiology, cleaning of premises and linen, chemical and biological analysis laboratories, etc.), are a major source of pollutant emissions into the environment (disinfectants, detergents, drug residues, etc.). Most of these pollutants can be found in hospital effluents (HWW), then in urban sewer networks and WWTP (weakly adapted for their treatment) and finally in aquatic environments. In view to evaluating the impact of these pollutants on aquatic ecosystems, it is necessary to characterise their ecotoxicity. Several reviews have focused on the quantitative and qualitative characterisation of pollutants present in HWW. However, none have focused specifically on the characterisation of their experimental ecotoxicity. We have evaluated this according to two complementary approaches: (i) a "substance" approach based on the identification of the experimental data in the literature for different substances found in hospital effluents, and on the calculation of their PNEC (Predicted Non Effect Concentration), (ii) a "matrix" approach for which we have synthesised ecotoxicity data obtained from the hospital effluents directly. This work first highlights the diversity of the substances present within hospital effluents, and the very high ecotoxicity of some of them (minimum PNEC observed close to 0,01. pg/L). We also observed that the consumption of drugs in hospitals was a predominant factor chosen by authors to prioritise the compounds to be sought. Other criteria such as biodegradability, excretion rate and the bioaccumulability of pollutants are considered, though more rarely. Studies of the ecotoxicity of the particulate phase of effluents must also be taken into account. It is also necessary to monitor the effluents of each of the specialised departments of the hospital studied. These steps is necessary to define realistic environmental management policies for hospitals (replacement of toxic products by less pollutant ones, etc.). © 2013 Elsevier B.V.
Griebler C.,Helmholtz Center Munich |
Malard F.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Lefebure T.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Current Opinion in Biotechnology | Year: 2014
Groundwater ecosystems constitute the largest terrestrial freshwater biome. They are dark, extremely low in energy and do not provide much space but they contain an unexpectedly high diversity of living forms showing characteristic adaptive features. The restricted accessibility along with the enormous 'invisible' heterogeneity challenged for a long time testing of scientific theories and unraveling of ecosystem functioning. Triggered by an improved interdisciplinarity, comprehensive sampling strategies and current developments in biotechnology and statistical analysis, groundwater ecology gains momentum entering a new era of research. We are only beginning to understand adaptive mechanisms, species distribution patterns and ecosystem functioning. Ninety-five percent of global liquid freshwater is stored in the terrestrial subsurface constituting a major source of water for drinking, irrigation and industrial purposes. There is an urgent need to integrate evolutionary and ecological research for developing a holistic perspective of the functional roles of biodiversity and ecosystem services and predicting global changes under alternative groundwater resource use scenarios. © 2014 Elsevier Ltd.
Hamann E.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory |
Puijalon S.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Annals of Botany | Year: 2013
Background and AimsWetlands are impacted by changes in hydrological regimes that can lead to periods of low water levels. During these periods, aquatic plants experience a drastic change in the mechanical conditions that they encounter, fromlowgravitational and tensile hydrodynamic forces when exposed to flowunder aquatic conditions, to high gravitational and bending forces under terrestrial conditions. The objective of this studywas to test the capacity of aquatic plants to produce self-supporting growth forms when growing under aerial conditions by assessing their resistance to terrestrial mechanical conditions and the associated morpho-anatomical changes. Methods Plastic responses to aerial conditionswere assessed by sampling Berula erecta, Hippuris vulgaris, Juncus articulatus, Lythrum salicaria, Mentha aquatica, Myosotis scorpioides, Nuphar lutea and Sparganium emersum under submerged and emergent conditions. The cross-sectional area and dry matter content (DMC) were measured in the plant organs that bear the mechanical forces, and their biomechanical properties in tension and bending were assessed. Key Results All of the species except for two had significantly higher stiffness in bending and thus an increased resistance to terrestrial mechanical conditions when growing under emergent conditions. This response was determined either by an increased allocation to strengthening tissues and thus a higher DMC, or by an increased cross-sectional area. These morpho-anatomical changes also resulted in increased strength and stiffness in tension. Conclusions The capacity of the studied species to colonize this fluctuating environment can be accounted for by a high degree of phenotypic plasticity in response to emersion. Further investigation is however needed to disentangle the finer mechanisms behind these responses (e.g. allometric relations, tissue make-up), their costs and adaptive value. © The Author 2013.
Feio M.J.,University of Coimbra |
Doledec S.,CNRS Ecology of Natural and Anthropized Hydrosystems Laboratory
Ecological Indicators | Year: 2012
Biological traits are increasingly used for describing ecological functioning of stream benthic assemblages. Such approaches associate information on species distribution to their biological characteristics (e.g. life history, physiology, dispersal ability) providing a biological trait profile of communities. They may complement structural bioassessment measures using taxonomic composition by providing indirect information on stream ecological functioning, with the additional advantage of being less constrained by biogeographic differences. A multivariate predictive model, that provides a site-specific list of expected taxa at least disturbed conditions was recently developed for the bioassessment of Portuguese streams. Here, we tested if the inclusion of trait information in the model would also enable the detection of most common anthropogenic disturbances (i.e.; organic contamination, hydrological disturbance) and provide diagnostic hints for causal relationships. We used existing information on 11 invertebrate biological traits and their 54 categories to convert the observed and expected taxonomic composition at several test sites into expected and observed trait compositions. The first three axes of a normalised PCA (Principal Components Analysis) performed on disturbance variables accounted for 42.7% of explained variability. The proportion of variance in disturbance explained by the three types of trait-based metrics (overall observed/expected trait composition, trait-category profile difference and traits profile dissimilarity) ranged between 9% and 32%. Our predictions made on the response of observed to expected trait categories for organic contamination were generally confirmed and demonstrated that disturbances resulted in a change in those traits conferring species resilience capacity and sensitivity to oxygen depletion, as well as a shift in the proportion of animals with filter-feeding behaviour. Variations in observed to expected trait-category differences showed that even a small increase in organic contamination led to a significant change in the biological trait profile, as expected. By contrast, only two out of 11 trait category predictions were confirmed for hydrological disturbance. Finally, we found that 4/11 and 9/11 observed to expected trait differences showed a significant deviation with organic contamination and hydrological disturbance, respectively, whereas all 11 observed to expected trait differences responded to overall disturbance. These changes in trait profiles reflect changes in the performance of invertebrate communities to cope with disturbance, which potentially can alter ecosystem functioning (e.g.; energy flow or chemical cycling). In conclusion, the integration of biological trait information in an AUSRIVAS type predictive model allowed the detection of a general disturbance gradient and particularly organic contamination, which indicates their value in addition to taxonomic-based assessment. © 2011 Elsevier Ltd. All rights reserved.