Résumé
The isotopic composition of dioxygen in the atmosphere is a global tracer which depends on the biosphere flux of dioxygen toward and from the atmosphere (photosynthesis and respiration) as well as exchanges with the stratosphere. When measured in fossil air trapped in ice cores, the relative concentration of 16O, 17O, and 18O of O2 can be used for several applications such as ice core dating and past global productivity reconstruction. However, there are still uncertainties about the accuracy of these tracers as they depend on the integrated isotopic discrimination of different biological processes of dioxygen production and uptake, for which we currently have very few independent estimates. Here we determined the respiration and photosynthesis fractionation factors for atmospheric dioxygen from experiments carried out in a replicated vegetation–soil–atmosphere analogue of the terrestrial biosphere in closed chambers with growing Festuca arundinacea. The values for 18O discrimination during soil respiration and dark respiration in leaves are equal to -12.3±1.7 ‰ and -19.1±2.4 ‰, respectively. In these closed biological chambers, we also found a value attributed to terrestrial photosynthetic isotopic discrimination equal to +3.7±1.3 ‰. This last estimate suggests that the contribution of terrestrial productivity in the Dole effect may have been underestimated in previous studies.
Auteurs, date et publication :
Auteurs Clémence Paul , Clément Piel , Joana Sauze , Nicolas Pasquier , Frédéric Prié , Sébastien Devidal , Roxanne Jacob , Arnaud Dapoigny , Olivier Jossoud , Alexandru Milcu , Amaëlle Landais
Publication : Biogeosciences
Date : 2023
Volume : 20
Issue : 5
Pages : 1047-1062
Catégorie(s)
#ANR-Citation #CNRS #Ecotron de MontpellierRésumé
Abstract
Turbidity challenges the visual performance of aquatic animals. During development, environments with limited visibility may affect the fine-tuning of visual systems and thus the perception of, and response to, risk. While turbidity has frequently been used to characterise permanent aquatic habitats, it has been an overlooked feature of ephemeral ones.
Here, we use the natural diversity of ephemeral rearing sites (phytotelmata) in which the tadpoles of two poison frog species are deposited and confined until metamorphosis to explore the relationship between environments with limited visibility and response to perceived risk.
We sampled wild tadpoles of
Dendrobates tinctorius
, a rearing-site generalist with facultatively cannibalistic tadpoles, and
Oophaga
(formerly
Dendrobates
)
pumilio
, a small-phytotelm specialist dependent on maternal food-provisioning, to investigate how the visual environment in rearing sites influences tadpole behaviour. We hypothesised that turbid rearing conditions negatively impact both species’ ability to perceive risk, decreasing response strength to predatory visual stimuli. Using experimental arenas, we measured tadpole activity and space first on a black and white background, and then on either black or white backgrounds where tadpoles were exposed to visual stimuli of (potentially cannibalistic) conspecifics or potential predators.
When placed in a novel arena, the effects of rearing environment on
D. tinctorius
tadpoles were clear: tadpoles from darker pools were less active than tadpoles from brighter pools, and did not respond to either visual stimuli, whereas tadpoles from brighter pools swam more when paired with conspecifics versus odonate larvae, suggesting that tadpoles can visually discriminate between predators. For
O. pumilio
, tadpoles were more active on experimental backgrounds that more closely matched the luminosity of their rearing sites, but their responses to the two visual stimuli did not differ.
Larval specialisation associated with species-specific microhabitat use may underlie the observed responses to visual stimuli, which has implications for the stability of species interactions and trophic dynamics in pool communities. Together, our findings demonstrate that light availability of wild larval rearing conditions influences the perception of risk in novel contexts, and provide insight into how visually guided animals may respond to sudden environmental disturbances.
Auteurs, date et publication :
Auteurs Chloe A. Fouilloux , Jennifer L. Stynoski , Carola A. M. Yovanovich , Bibiana Rojas
Date : 2023
Catégorie(s)
#CNRS #FORET NouraguesRésumé
The predicted increases in drought in many forest ecosystems may alter soil microbial community diversity and activity, which may further depend on tree species richness. Shifts in microbial community composition and activity could engender changes in ecosystem function, notably, in soil greenhouse gas emissions and C storage. Using soils from mono-specific and mixed three-species forest stands from across Europe, we performed a microcosm experiment to test how soil microbial taxonomic and catabolic diversity are affected by repeated drying-rewetting (DRW) cycles and tree species mixing. We used Illumina sequencing and MicroResp™ analyses to explore community-level changes between microbial functional groups. DRW decreased bacterial richness and carbon substrate use diversity and increased fungal Shannon diversity. Additionally, microbial communities exposed to DRW changed their consumption of 11 out of 15 substrates significantly, suggesting microbial functional shifts. The legacy effect of tree species mixing influenced the structure of the microbial communities (i.e. taxonomic differential abundance) although, community weighted mean (CWM) values of absorptive root traits appeared to affect more strongly microbial richness, relative abundance, and Shannon diversity. No significant tree species mixing:DRW interaction was found for most microbial variables, except for the use of certain substrates and potentially differential abundance. Our data from a laboratory experiment with soils from different forest ecosystems underline that drought may cause shifts in microbial taxonomic and catabolic diversity, while tree species influences primarily taxonomic diversity through root traits.
Auteurs, date et publication :
Auteurs Lauren M. Gillespie , Luis Daniel Prada-Salcedo , Ammar Shihan , Nathalie Fromin , Kezia Goldmann , Alexandru Milcu , François Buscot , Bruno Buatois , Stephan Hättenschwiler
Publication : Pedobiologia
Date : 2023
Volume : 97-98
Pages : 150875
Catégorie(s)
#ANR-Citation #CNRS #Ecotron de MontpellierRésumé
Causal effects of biodiversity on ecosystem functions can be estimated using experimental or observational designs — designs that pose a tradeoff between drawing credible causal inferences from correlations and drawing generalizable inferences. Here, we develop a design that reduces this tradeoff and revisits the question of how plant species diversity affects productivity. Our design leverages longitudinal data from 43 grasslands in 11 countries and approaches borrowed from fields outside of ecology to draw causal inferences from observational data. Contrary to many prior studies, we estimate that increases in plot-level species richness caused productivity to decline: a 10% increase in richness decreased productivity by 2.4%, 95% CI [−4.1, −0.74]. This contradiction stems from two sources. First, prior observational studies incompletely control for confounding factors. Second, most experiments plant fewer rare and non-native species than exist in nature. Although increases in native, dominant species increased productivity, increases in rare and non-native species decreased productivity, making the average effect negative in our study. By reducing the tradeoff between experimental and observational designs, our study demonstrates how observational studies can complement prior ecological experiments and inform future ones.
Auteurs, date et publication :
Auteurs Laura E. Dee , Paul J. Ferraro , Christopher N. Severen , Kaitlin A. Kimmel , Elizabeth T. Borer , Jarrett E. K. Byrnes , Adam Thomas Clark , Yann Hautier , Andrew Hector , Xavier Raynaud , Peter B. Reich , Alexandra J. Wright , Carlos A. Arnillas , Kendi F. Davies , Andrew MacDougall , Akira S. Mori , Melinda D. Smith , Peter B. Adler , Jonathan D. Bakker , Kate A. Brauman
Publication : Nature Communications
Date : 2023
Volume : 14
Issue : 1
Pages : 2607
Catégorie(s)
#ANR-Citation #CEREEP #CNRS #ENSRésumé
A new species of Hypaeus Simon 1900 is described from French Guiana based on both sexes, Hypaeus olympeae sp. nov. We employed morphological evidence, field observation, as well as the mitochondrial COI rapidly evolving loci to confirm that both males and females belong to the same species. Finally, nine species are newly recorded for the salticid fauna of French Guiana, Cyllodania fasciata (Caporicaco, 1954) syn. nov. is considered junior synonym of Gypogyna forceps Simon, 1900 and 12 COI sequences corresponding to four previously unsequenced Hypaeus species are added to GenBank.
Auteurs, date et publication :
Auteurs Cyril Courtial , Kaïna Privet , Xavier Aubriot , Lionel Picard , Julien Pétillon
Publication : Studies on Neotropical Fauna and Environment
Date : 2023
Volume : 58
Issue : 2
Pages : 439-447
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Microalgae remain an exciting target for biotechnology as they offer a largely unexploited reservoir of novel and valuable bioactive compounds. Strain improvement programs are an expanding research field aiming to multiply microalgal potential. This study evaluates the genetic diversity created in populations of the diatom Phaeodactylum tricornutum subjected to random mutagenesis. We explored the genetic diversity using genotyping-by-sequencing (GBS) to estimate and compare the impact of the most common chemical mutagen (ethyl methanesulfonate, EMS). Five microalga populations obtained following EMS treatment had survival rates between 1 and 98 %. High genetic diversity was obtained for only one of these P. tricornutum populations, with a survival rate close to 30 %.
Auteurs, date et publication :
Auteurs Judith Rumin , Grégory Carrier , Catherine Rouxel , Aurélie Charrier , Virginie Raimbault , Jean-Paul Cadoret , Gaël Bougaran , Bruno Saint-Jean
Publication : Algal Research
Date : 2023
Volume : 74
Pages : 103148
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
The neotropical Apicotermitinae is a common and widespread clade of mostly soil-feeding soldierless termites. With few exceptions, species of this group were originally assigned to the genus Anoplotermes Müller, 1873. The application of internal worker morphology coupled with genetic sequencing has recently shed light on the true diversity of this subfamily. Herein, Anoplotermes susanae Scheffrahn, Carrijo & Castro, sp. nov. and four new species in four new genera are described: Hirsutitermes kanzakii Scheffrahn, Carrijo & Castro, gen. nov. et sp. nov., Krecekitermes daironi Scheffrahn, Carrijo & Castro, gen. nov. et sp. nov., Mangolditermes curveileum Scheffrahn, Carrijo & Castro, gen. nov. et sp. nov., and Ourissotermes giblinorum Scheffrahn, Carrijo & Castro, gen. nov. et sp. nov. Worker descriptions are based mainly on worker gut morphology, including the enteric valve, while imagoes were described based on external characters. A Bayesian phylogenetic tree of New World Apicotermitinae was constructed using the complete mitogenome to infer genera relationships and corroborate the taxonomic decisions. Distribution maps and a dichotomic key to the known Neotropical Apicotermitinae genera are provided.
Auteurs, date et publication :
Auteurs Tiago F. Carrijo , Daniel Castro , Menglin Wang , Joice P. Constantini , Thomas Bourguignon , Eliana M. Cancello , Yves Roisin , Rudolf H. Scheffrahn
Publication : ZooKeys
Date : 2023
Volume : 1167
Pages : 317-352
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Triple oxygen isotopes (17O-excess) of water are useful to trace evaporation at the soil–plant–atmosphere interface. The 17O-excess of plant silica, i.e., phytoliths, inherited from leaf water, was previously calibrated in growth chambers as a proxy of atmospheric relative humidity (RH). Here, using a model–data approach, we examine the parameters that control the triple oxygen isotope composition of bulk grass leaf water and phytoliths in natura, at the O3HP experimental platform located in the French Mediterranean area. A grass plot was equipped to measure for 1 year, all environmental and plant physiological parameters relevant for modeling the isotope composition of the grass leaf water. In particular, the triple oxygen and hydrogen isotope composition of atmospheric water vapor above the grass was measured continuously using a cavity ring-down spectrometer, and the grass leaf temperature was monitored at plot scale using an infrared (IR) radiometer. Grass leaves were collected in different seasons of the year and over a 24 h period in June. Grass leaf water was extracted by cryogenic vacuum distillation and analyzed by isotope ratio mass spectrometry (IRMS). Phytoliths were analyzed by IR–laser fluorination–IRMS after chemical extraction. We showed that the traditional Craig–Gordon steady-state model modified for grass leaves reliably predicts the triple oxygen isotope composition of leaf water during daytime but is sensitive to uncertainties on the leaf-to-air temperature difference. Deviations from isotope steady state at night are well represented in the triple oxygen isotope system and predictable by a non-steady-state model. The 17O-excess of phytoliths confirms the applicability of the 17O-excessphyto vs. RH equation established in previous growth chamber experiments. Further, it recorded average daytime RH over the growth period rather than daily RH, related to low transpiration and silicification during the night. This model–data approach highlights the utility of the triple oxygen isotope system to improve the understanding of water exchange at the soil–plant–atmosphere interface. The in natura experiment underlines the applicability of 17O-excess of phytoliths as a RH proxy.
Auteurs, date et publication :
Auteurs Claudia Voigt , Anne Alexandre , Ilja M. Reiter , Jean-Philippe Orts , Christine Vallet-Coulomb , Clément Piel , Jean-Charles Mazur , Julie C. Aleman , Corinne Sonzogni , Helene Miche , Jérôme Ogée
Publication : Biogeosciences
Date : 2023
Volume : 20
Issue : 11
Pages : 2161-2187
Catégorie(s)
#ANR-Citation #CNRS #Ecotron de Montpellier #FORET O3HPRésumé
Clonostachys (Bionectriaceae, Hypocreales) species are common soil-borne fungi, endophytes, epiphytes, and saprotrophs. Sexual morphs of Clonostachys spp. were placed in the genus Bionectria, which was further segregated into the six subgenera Astromata, Bionectria, Epiphloea, Myronectria, Uniparietina, and Zebrinella. However, with the end of dual nomenclature, Clonostachys became the single depository for sexual and asexual morphtypified species. Species of Clonostachys are typically characterised by penicillate, sporodochial, and, in many cases, dimorphic conidiophores (primary and secondary conidiophores). Primary conidiophores are mononematous, either verticillium-like or narrowly penicillate. The secondary conidiophores generally form imbricate conidial chains that can collapse to slimy masses, particularly on sporodochia. In the present study, we investigated the species diversity within a collection of 420 strains of Clonostachys from the culture collection of, and personal collections at, the Westerdijk Fungal Biodiversity Institute in Utrecht, the Netherlands. Strains were analysed based on their morphological characters and molecular phylogeny. The latter used DNA sequence data of the nuclear ribosomal internal transcribed spacer regions and intervening 5.8S nrDNA (ITS) and partial 28S large subunit (LSU) nrDNA and partial protein encoding genes including the RNA polymerase II second largest subunit (RPB2), translation elongation factor 1-alpha (TEF1) and β-tubulin (TUB2). Based on these results, the subgenera Astromata, Bionectria, Myronectria and Zebrinella are supported within Clonostachys. Furthermore, the genus Sesquicillium is resurrected to accommodate the former subgenera Epiphloea and Uniparietina. The close relationship of Clonostachys and Sesquicillium is strongly supported as both are inferred phylogenetically as sister-genera. New taxa include 24 new species and 10 new combinations. Recognition of Sesquicillium distinguishes species typically forming a reduced perithecial stroma superficially on plant tissue from species in Clonostachys often forming well-developed, through bark erumpent stromata. The patterns of observed perithecial wall anatomies, perithecial wall and stroma interfaces, and asexual morph diversifications described in a previously compiled monograph are used for interpreting ancestral state reconstructions. It is inferred that the common ancestor of Clonostachys and Sesquicillium may have formed perithecia superficially on leaves, possessed a perithecial wall consisting of a single region, and formed intercalary phialides in penicilli of conidiophores. Character interpretation may also allow hypothesising that diversification of morphs occurred then in the two genera independently and that the frequently stroma-linked Clonostachys morphs evolved together with the occupation of woody host niches and mycoparasitism.
Auteurs, date et publication :
Auteurs L. Zhao , J.Z. Groenewald , M. Hernández-Restrepo , H.-J. Schroers , P.W. Crous
Publication : Studies in Mycology
Date : 2023
Volume : 105
Issue : 1
Pages : 204-265
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Abstract. Saharan dust outbreaks have profound effects on ecosystems, climate, human health, and the cryosphere in Europe. However, the spatial deposition pattern of Saharan dust is poorly known due to a sparse network of ground measurements. Following the extreme dust deposition event of February 2021 across Europe, a citizen science campaign was launched to sample dust on snow over the Pyrenees and the European Alps. This somewhat improvised campaign triggered wide interest since 152 samples were collected from the snow in the Pyrenees, the French Alps, and the Swiss Alps in less than 4 weeks. Among the 152 samples, 113 in total could be analysed, corresponding to 70 different locations. The analysis of the samples showed a large variability in the dust properties and amount. We found a decrease in the deposited mass and particle sizes with distance from the source along the transport path. This spatial trend was also evident in the elemental composition of the dust as the iron mass fraction decreased from 11 % in the Pyrenees to 2 % in the Swiss Alps. At the local scale, we found a higher dust mass on south-facing slopes, in agreement with estimates from high-resolution remote sensing data. This unique dataset, which resulted from the collaboration of several research laboratories and citizens, is provided as an open dataset to benefit a large community and to enable further scientific investigations. Data presented in this study are available at https://doi.org/10.5281/zenodo.7969515 (Dumont et al., 2022a).
Auteurs, date et publication :
Auteurs Marie Dumont , Simon Gascoin , Marion Réveillet , Didier Voisin , François Tuzet , Laurent Arnaud , Mylène Bonnefoy , Montse Bacardit Peñarroya , Carlo Carmagnola , Alexandre Deguine , Aurélie Diacre , Lukas Dürr , Olivier Evrard , Firmin Fontaine , Amaury Frankl , Mathieu Fructus , Laure Gandois , Isabelle Gouttevin , Abdelfateh Gherab , Pascal Hagenmuller
Publication : Earth System Science Data
Date : 2023
Volume : 15
Issue : 7
Pages : 3075-3094