Biology subjects

Danger, M.

Publications and source records attributed to Danger, M..

4 recordsLinked to original sources

bioRxiv2024

Effects of water nutrient concentrations on stream macroinvertebrate community stoichiometry: a large-scale study

Basal resources generally mirror environmental nutrient concentrations in the elemental composition of their tissue, meaning that nutrient alterations can directly reach consumer level. An increased nutrient content (e.g. phosphorus) in primary and detrital resources under nutrient enriched conditions should favour taxa with a high demand for this nutrient. With the nutrient demand of a taxon being correlated to the elemental composition of its body tissue (e.g. phosphorus content), such above described species shifts likely alter the overall community stoichiometry. However, studies addressing stoichiometry at community level are rare and most often restricted to lacustrine planktonic systems, single streams or limited experimental setups. Relying on a stoichiometric database for >200 taxa and >1300 standardized sampling events of macroinvertebrate assemblages from the French national monitoring programme, we investigated the effect of water phosphorus and nitrogen load on stream macroinvertebrate community stoichiometry. Community stoichiometry was significantly affected by water phosphorus concentration and the effect was strongest at low levels of nitrogen. While we could not confirm our hypothesis of increasing community %P (and decreasing C:P, N:P) with increasing water phosphorus concentrations for the overall community, it clearly followed this pattern for both Insecta and Malacostraca. General differences in the elemental composition among major taxonomic groups and a shift among these groups over the nutrient gradient probably explain the response of community stoichiometry. Our results show that assumptions from Ecological Stoichiometry Theory also hold at the community level, at least for two dominant taxa, and on a large spatial scale, with likely consequences for nutrient cycling and ecosystem function.

ecology↗

bioRxiv2020

Body stoichiometry of heterotrophs: assessing drivers of interspecific variations in elemental composition.

AimTo document how body stoichiometry of heterotrophs varies globally and to assess phylogenetic, trophic, habitat and body mass drivers of this interspecific variation in elemental composition, focusing on carbon (C), nitrogen (N) and phosphorus (P). LocationWorldwide. Time period1930 - 2018. Major taxa studiedAmphibians, fishes (Euteleosteomorpha and Otomorpha), invertebrates, mammals, microbes and sauropsids (birds and reptiles). MethodsWe compiled from the scientific literature a global database of body elemental composition of heterotrophs in marine, freshwater and terrestrial realms. We used model selection and ANCOVA analyses to investigate the proportion of variance in elemental composition explained by taxonomic groups, diet, habitat and body mass. We assessed the phylogenetic signal in body stoichiometry using Blombergs K and Pagels {lambda} statistics. We assessed the phylogenetic structure of interspecific variation in body stoichiometry using mixed models with nested taxonomic levels as random factors. We finally assessed the co-variation in elemental composition using linear models. ResultsOur database currently gathers 17848 independent observations on 1491 species. Body elemental composition was found to be widely variable among species with the four assessed drivers significantly contributing to this variation. Taxonomic group is the strongest contributor to interspecific variance for the stoichiometric traits studied, followed by habitat, diet and body mass. More precisely, stoichiometric traits are generally variable at the three taxonomic levels studied (class, order and family), resulting in a significant but relatively modest phylogenetic signal. Finally, we found significant co-variation among the three body elemental contents, resulting in taxonomic group-specific C:N:P spectrums. Main conclusionsOur global synthesis of body stoichiometry of heterotrophs reveals a strong interspecific variability that is only modestly explained by the species attributes investigated: body mass, habitat and diet. It further reveals that this taxonomically structured residual variation in body stoichiometry seems to be constrained along taxonomic group-specific elemental spectrums.

ecology↗

bioRxiv2019

The Threshold Elemental Ratio of an ectotherm decreases then increases with rising temperature

Earth is currently facing unprecedented global changes, hurrying scientists to provide predictive tools to explore the futures responses of ecosystems. Among those changes, temperature increase and alterations of nutrient availabilities largely drive consumer performances, yet their interactive effect remains poorly understood. Here we investigate how the dietary C:P ratio that optimizes consumer growth (TERC:P: Threshold Elemental Ratio) changes along temperature gradients by combining a TERC:P model and growth experiments on the model organism Daphnia magna. Both lines of evidence show that the TERC:P responds to temperature in an U-shaped fashion. This shape reconciles previous contradictive observations into a common framework, thereby improving our capacity to forecast the combined effects of nutrient cycle and climatic alterations on ectotherms.

ecology↗

bioRxiv2018

A microcalorimetric approach for investigating stoichiometric constraints on the standard metabolic rate of a small invertebrate

1: Understanding the determinant of metabolism is a core ecological topic since it permits to link individuals energetic requirements to the ecology of communities and ecosystems. Yet, besides temperature, the effects of environmental factors on metabolism remain poorly understood. For example, dietary stoichiometric constraints have been hypothesized to increase maintenance metabolism of small invertebrates, yet experimental support remains scarce.\n\n2: Here, we used microcalorimetric heat flow measurements to determine the standard metabolic rate (SMR) of Daphnia magna throughout its ontogeny when fed stoichiometrically balanced (C/P ratio:166) or imbalanced (C/P ratio:1439) diets.\n\n3: When fed a stoichiometrically imbalanced diet, daphnids were able to maintain the stoichiometric homeostasis within narrow boundaries. However, they consistently increased their SMR while decreasing their somatic growth rate. Our measurements unequivocally demonstrate that homeostatic regulation implies higher metabolic costs and thereby reduces the portion of energy that can be allocated to growth.\n\n4: Our study demonstrates that microcalorimetry is a powerful and precise tool for measuring the metabolic rate of small-sized organisms and opens promising perspectives for understanding how environmental factors, such as nutritional constraints, affect organismal metabolism.

ecology↗