Showing papers by "Régis Céréghino published in 2017"
TL;DR: In this article, the authors used chemical and ecological data collected in the Nestore river basin (Central Italy) to test whether there are generalities in the response of macroinvertebrate functional diversity to river pollution; water pollution filters certain functional traits and traits do better than chemical analyses at revealing ecological stress in rivers.
Abstract: Both physical–chemical and biological indicators are used to assess the ecological health of ecosystems. The functional trait composition of communities has the potential to predict the impact of environmental change on ecosystems, yet, we miss evidence that information on pollution can be used to forecast the functional responses of freshwater communities. We used chemical and ecological data collected in the Nestore river basin (Central Italy) to test whether (i) there are generalities in the response of macroinvertebrate functional diversity to river pollution; (ii) water pollution filters certain functional traits and (iii) traits do better than chemical analyses at revealing ecological stress in rivers. Due to interactions with hydrology, chemical variables showed higher seasonal variation at impacted sites, so occasional water samples represented snapshots. Functional traits did well at detecting water pollution by various chemicals, and there was a clear shift of trait combinations from unimpacted to impacted sites. Anthropogenic disturbances homogenized benthic communities in terms of taxonomic and functional composition, both in space (impacted sites) and time (seasons). Traits related to feeding habits (mainly reliance on fine particulate organic matter) and tolerance to organic pollution were prevalent at impacted reaches, and functional trait compositions were more stable than water chemistry over seasons because they integrate environmental conditions over longer time periods. Functional traits can play a relevant role in the bioassessment of polluted river ecosystems, even under low to moderate disturbance. Trait-based assessment can be complemented by chemical analyses, notably at highly polluted sites where biological diversity drops to its lowest levels. Copyright © 2016 John Wiley & Sons, Ltd.
36 citations
TL;DR: The results suggest that changes in species distribution that will affect population dynamics through biotic interactions in space and/or time could have greater effects on food webs and ecosystem functioning than changes in environmental factors per se.
Abstract: Tank bromeliads form a conspicuous, yet neglected freshwater habitat in Neotropical forests. Recent studies driven by interests in medical entomology, fundamental aspects of bromeliad ecology and experimental research on food webs have, however, prompted increasing interest in bromeliad aquatic ecosystems. As yet, there is nothing in the literature about the life histories and environmental drivers of invertebrate population dynamics in tank bromeliads. Based on fortnightly samples taken over oneyear, size frequency plots and individual dry masses allowed us to establish the life cycles and growth rates of the dominant aquatic invertebrates in a common bromeliad species of French Guiana. Linear mixed-effect models and Mantel tests were used to predict changes in density, biomass, and growth rates in relation to temperature, rainfall, humidity and detrital resources. Annual variations in invertebrate densities and biomasses could be described according to three types of distribution: unimodal, bimodal or almost constant. Despite seasonal variations, precipitation, temperature, relative humidity and detritus concentration accounted significantly for changes in density and biomass, but we found no significant responses in growth rates of most invertebrate species. Species rather displayed non-seasonal life cycles with overlapping cohorts throughout the year. There was also a trend for delayed abundance peaks among congeneric species sharing similar functional traits, suggesting temporal partitioning of available resources. Beyond novel knowledge, quantitative information on life histories is important to predict food-web dynamics under the influence of external forcing and self-organisation. Our results suggest that changes in species distribution that will affect population dynamics through biotic interactions in space and/or time could have greater effects on food webs and ecosystem functioning than changes in environmental factors per se.
32 citations
TL;DR: The results suggest that the plasticity of the tank bromeliad A. mertensii is mainly due to environment but also to genetic differences related to seed origin, as some traits are heritable.
Abstract: Plant germination and development depend upon a seed's successful dispersal into a suitable habitat and its ability to grow and survive within the surrounding biotic and abiotic environment. The seeds of Aechmea mertensii, a tank-bromeliad species, are dispersed by either Camponotus femoratus or Neoponera goeldii, two ant species that initiate ant gardens (AGs). These two mutualistic ant species influence the vegetative and reproductive traits of the bromeliad through their divergent ecological preferences (i.e. light and substrate). We hypothesised that the seeds dispersed by these two ant species have underlying genetic differences affecting germination, growth and survival of A. mertensii seedlings in different ways. To test this, we used an experimental approach consisting of sowing seeds of A. mertensii: (i) taken from the two AG-ant associations (i.e. seed origin), (ii) in two contrasting light conditions, and (iii) on three different substrates. Light and substrate had significant effects on germination, survival and on eight key leaf traits reflecting plant performance. Seed origin had a significant effect only on germination and on two leaf traits (total dry mass and relative growth rate). Overall, this bromeliad performs better (i.e. high growth and survival rates) when growing both in the shade and in the carton nest developed by C. femoratus ants. These results suggest that the plasticity of the tank bromeliad A. mertensii is mainly due to environment but also to genetic differences related to seed origin, as some traits are heritable. Thus, these two ant species may play contrasting roles in shaping plant evolution and speciation.
23 citations
TL;DR: This study shows that small monospecific stands are likely sustainable when embedded in the rainforest and that environmentally-friendly strategies can be planned accordingly.
20 citations
TL;DR: The results pose the question of when does environmental determinism matter for ecosystem functions, and when does it not.
Abstract: Decomposition experiments that control leaf litter species across environments help to disentangle the roles of litter traits and consumer diversity, but once we account for leaf litter effects, they tell us little about the variance in decomposition explained by shifts in environmental conditions versus food-web structure We evaluated how habitat, food-web structure, leaf litter species, and the interactions between these factors affect litter mass loss in a neotropical ecosystem We used water-filled bromeliads to conduct a reciprocal transplant experiment of two litter species between an open and a forested habitat in French Guiana, and coarse- and fine-mesh enclosures embedded within bromeliads to exclude invertebrates or allow them to colonize leaf litter disks Soft Melastomataceae leaves decomposed faster in their home habitat, whereas tough Eperua leaves decomposed equally in both habitats Bacterial densities did not differ significantly between the two habitats Significant shifts in the identity and biomass of invertebrate detritivores across habitats did not generate differences in leaf litter decomposition, which was essentially microbial Despite the obvious effects of habitats on food-web structure, ecosystem processes are not necessarily affected Our results pose the question of when does environmental determinism matter for ecosystem functions, and when does it not
17 citations
TL;DR: Investigation of the taxonomic and functional diversity patterns of the aquatic macroinvertebrate communities in tank bromeliads by comparing those found in a small Neotropical city with those from an adjacent rural site found changes in the quality of detrital inputs in relation to lower tree diversity and the presence of synanthropic species.
Abstract: Due to habitat fragmentation, resource disruption and pollution, urbanization is one of the most destructive forms of anthropization affecting ecosystems worldwide. Generally, human-mediated perturbations dramatically alter species diversity in urban sites compared to the surroundings, thus influencing the functioning of the entire ecosystem. We investigated the taxonomic and functional diversity patterns of the aquatic macroinvertebrate communities in tank bromeliads by comparing those found in a small Neotropical city with those from an adjacent rural site. Changes in the quality of detrital inputs in relation to lower tree diversity and the presence of synanthropic species are likely important driving forces behind the observed structural changes in the urban site. Leaf-litter processors (i.e., shredders, scrapers) were positively affected in the urban site, while filter-feeders that process smaller particles produced by the activity of the shredders were negatively affected. Because we cannot ascertain whether the decline in filter-feeders is related to food web-mediated effects or to competitive exclusion (Aedes aegypti mosquitoes were present in urban bromeliads only), further studies are necessary to account for the effects of intra-guild competition or inter-guild facilitation.
17 citations
TL;DR: In this article, a macroinvertebrate multimetric index that fulfills the requirements of the EU Water Framework Directive and measures ecological health as a deviation from a reference state, taking into consideration water and sediment contamination in streams of Central Italy.
Abstract: Environmental issues and their associated legislative pressures are demanding, especially regarding costs, limited budgets, and data collection efforts. The development of effective biotic indices for monitoring generated via comprehensive data collection within human-impacted landscapes can support district- to regional-level environmental management plans. We designed a macroinvertebrate multimetric index that fulfills the requirements of the EU Water Framework Directive and measures ecological health as a deviation from a reference state, taking into consideration water and sediment contamination in streams of Central Italy. Macroinvertebrate samples were obtained by a semi-quantitative technique. The Semi-quantitative Multimetric Index (SMI) we developed has a high discrimination efficiency (reference vs. impacted sites), high stability (i.e., low coefficient of variation) at reference sites, and low specificity regarding the environmental variables reflecting contamination. The SMI is compose...
11 citations
TL;DR: In this article, the aerial dispersal of multiple interacting species and the formation of aquatic communities are linked by a process occurring in both the aquatic and terrestrial compartments of the ecosystem.
Abstract: Context
Many aquatic communities are linked by the aerial dispersal of multiple, interacting species and are thus structured by processes occurring in both the aquatic and terrestrial compartments of the ecosystem.
8 citations