Résumé
Individual-based forest models (IBMs) are useful to investigate the effect of environment on forest structure and dynamics, but they are often restricted to site-specific applications. To build confidence for spatially distributed simulations, model transferability, i.e. the ability of the same model to provide reliable predictions at contrasting sites, has to be thoroughly tested. We tested the transferability of a spatially explicit forest IBM, TROLL, with a trait-based species parameterization and global gridded climate forcing, by applying it to two sites with sharply contrasting climate and floristic compositions across the tropics, one in South America and one in Southeast Asia. We identified which parameters are most influential for model calibration and assessed the model sensitivity to climatic conditions for a given calibration. TROLL produced realistic predictions of forest structure and dynamics at both sites and this necessitates the recalibration of only three parameters, namely photosynthesis efficiency, crown allometry and mortality rate. All three relate to key processes that constrain model transferability and warrant further model development and data acquisition, with mortality being a particular priority of improvement for the current generation of vegetation models. Varying the climatic conditions at both sites demonstrate similar, and expected, model responses: GPP increased with temperature and irradiance, while stem density and aboveground biomass declined as temperature increased. The climate dependence of productivity and biomass was mediated by plant respiration, carbon allocation and mortality, which has implications both on model development and on forecasting of future carbon dynamics. Our detailed examination of forest IBM transferability unveils key processes that need to improve in genericity before reliable large-scale implementations can be envisioned.
Auteurs, date et publication :
Auteurs E-Ping Rau , Fabian Fischer , Émilie Joetzjer , Isabelle Maréchaux , I Fang Sun , Jérôme Chave
Publication : Ecological Modelling
Date : 2022
Volume : 463
Pages : 109801
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Soil organic carbon is regulated by a dynamic interaction of vegetation inputs, organic matter degradation and stabilization processes in soils, and its redistribution in the landscape. Tropical ecosystems are highly important in terms of carbon stored in vegetation and soil, but many processes of the soil carbon cycle in the tropics are yet to be fully understood. Here, we studied soil organic carbon stocks and quality in small-scale tropical, sub-humid and semi-arid watersheds along a climate gradient in southwestern India with varying vegetation and geology to identify major drivers of soil organic carbon dynamics in three prevalent soil types (Lixisol, Vertisol and Ferralsol) under shrubland and dry deciduous forest. We used a combination of organic carbon analysis (total organic carbon content, 13C, C:N), mid-infrared spectroscopy and soil property information (bulk density, texture, oxides, pH, cation-exchange capacity). Soil organic carbon stocks in these watersheds showed a substantial range from 58.2 to 169.4 MgCha−1 in the first 60 cm, and the differences depended on local- to watershed-scale variations in vegetation type and history, geology, soil physio-chemical (clay, oxides) and biological (bioturbation) properties. Considerable parts of the organic carbon stored in these soils was found below 30 cm (up to 40%), stressing the importance of tropical subsoils. From our analysis of the soil organic carbon quality and literature data on paleoclimate and vegetation, we could identify land-use changes in these watersheds, from tropical moist evergreen forests, forest-savannah transitions and plantations to secondary regrowth forest over time. Our study provides new data and insights into the local-scale drivers of soil organic carbon quantity and quality of tropical, sub-humid and semi-arid watersheds under shrubland and dry deciduous forest with varying geology and soil types.
Auteurs, date et publication :
Auteurs Severin-Luca Bellè , Jean Riotte , Muddu Sekhar , Laurent Ruiz , Marcus Schiedung , Samuel Abiven
Publication : Geoderma
Date : 2022
Volume : 409
Pages : 115606
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSRésumé
The intestines of wild Caenorhabditis nematodes are inhabited by a variety of microorganisms, including gut microbiome bacteria and pathogens, such as microsporidia and viruses. Because of the similarities between Caenorhabditis elegans and mammalian intestinal cells, as well as the power of the C. elegans system, this host has emerged as a model system to study host intestinemicrobe interactions in vivo. While it is possible to observe some aspects of these interactions with bright-field microscopy, it is difficult to accurately classify microbes and characterize the extent of colonization or infection without more precise tools.
Auteurs, date et publication :
Auteurs Dalaena E Rivera , Vladimir Lažetić , Emily R Troemel , Robert J Luallen
Publication : Journal of Visualized Experiments
Date : 2022
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Although irrigation water is frequently assessed for the presence of plant pathogens, large spatial and temporal surveys that provide clues on the diversity and circulation of pathogens is missing. We evaluate the diversity of soft rot Pectobacteriaceae (SRP) of the genera Dickeya and Pectobacterium over two years in a temperate, mixed use watershed. The abundance of isolated strains correlates with the agricultural gradient along the watershed with a positive correlation found with temperature, nitrate and dissolved organic carbon water concentration. We characterized 582 strains by amplification and sequencing of the gapA gene. MLSA analysis performed with 3 housekeeping genes for 99 strains and core genome analysis of 38 sequenced strains confirmed for all the strains but one the taxonomic assignation obtained with the sole gapA sequence. Pectobacterium spp. (549 isolates) were far more abundant than Dickeya spp. (33 isolates). Dickeya spp. were only observed in the lower part of the river when water temperature was above 19°C and we experimentally confirmed a decreased fitness of several Dickeya spp. at 8°C in river water. D. oryzae dominates the Dickeya spp. P. versatile and P. aquaticum dominate the Pectobacterium spp. but their repartition along the watershed was different, P. versatile being the only species regularly recovered all along the watershed. Excepting P. versatile, Dickeya and Pectobacterium spp. responsible for disease outbreak on crops were less abundant or rarely detected. This work sheds light on the various ecological behaviours of different SRP in stream water and indicates that SRP occupation is geographically structured.
Auteurs, date et publication :
Auteurs Hajar Ben Moussa , Claire Bertrand , Emma Rochelle-Newall , Sarah Fiorini , Jacques Pédron , Marie-Anne Barny
Publication : Phytopathology
Date : 2022
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENS #PLANAQUARésumé
Precise identification of anopheline species is paramount for incrimination of malaria vectors and implementation of a sustainable control program. Anopheline mosquitoes are routinely identified morphologically, a technique that is time-consuming, needs high level of expertise, and prone to misidentifications especially when considering Amazonian species. The aim of this study was therefore to develop a DNA-based identification technique to supplement traditional morphological identification methods for the discrimination of anopheline mosquitoes collected in French Guiana.The internal transcribed spacer 2 (ITS2) region of ribosomal DNA (rDNA) for anopheline species was amplified by polymerase chain reaction (PCR), and digested with AluI/MspI restriction enzymes. PCR-restriction fragments length polymorphism (RFLP) assay was compared to sequencing of the ITS2 region for validation. Fifteen Anopheles species have shown distinct PCR-RFLP profiles. A concordance of 100% was obtained when identification by PCR-RFLP was compared to sequencing of ITS2. A high throughput, fast, and cost-effective PCR-RFLP assay has been developed for unambiguous discrimination of fifteen anopheline mosquito species from French Guiana including primary and suspected secondary malaria vectors.
Auteurs, date et publication :
Auteurs S B Vezenegho , J Issaly , R Carinci , P Gaborit , R Girod , Isabelle Dusfour , S Briolant , Maria Anice Sallum
Publication : Journal of Medical Entomology
Date : 2022
Volume : 59
Issue : 3
Pages : 1060-1064
Catégorie(s)
#CNRS #FORET NouraguesRésumé
The genus Pipa is a species-poor clade of Neotropical frogs and one of the most bizarre-looking due to many highly derived anatomical traits related to their fully aquatic lifestyle. With their African relatives, they form the Pipidae family, which has attracted much attention, especially regarding its anatomy, reproductive biology, paleontology and biogeography. However, the actual diversity and phylogenetic relationships within Pipa remain poorly understood, and thus so do their historical biogeography and the evolution of striking features, such as the absence of teeth and endotrophy in some species. Using short mtDNA sequences across the distribution of the genus, we identified 15 main lineages (Operational Taxonomic Units - OTUs). This more than doubles the number of the currently seven valid nominal species. Several closely related OTUs do not share nuDNA alleles, confirming species divergence. Time-calibrated phylogenies obtained from mitogenomes and from 10 nuclear loci provide highly similar topologies but strikingly distinct node ages for Pipa. High dN/dS ratios and the variation of substitution rates across the trees suggest a strong effect of saturation on fast evolving positions of mtDNA, producing a substantially shorter stem branch of Pipa. Focusing on the nuDNA topology, we inferred an early Neogene Amazonian origin of the diversification of Pipa, with an initial split between the Guiana-Brazilian Shields and Western Amazonia, a pattern observed in many other co-distributed groups. All the western species are edentate, suggesting a single loss in the genus. Each of these groups diversified further out of Amazonia, toward the Atlantic Forest and toward trans-Andean forests, respectively. These events are concomitant with paleogeographic changes and match patterns observed in other co-distributed taxonomic groups. The two Amazonian lineages have probably independently acquired endotrophic larval development.
Auteurs, date et publication :
Auteurs Antoine Fouquet , Josselin Cornuault , Miguel T. Rodrigues , Fernanda P. Werneck , Tomas Hrbek , Andres R. Acosta-Galvis , David Massemin , Philippe J. R. Kok , Raffael Ernst
Publication : MOLECULAR PHYLOGENETICS AND EVOLUTION
Date : 2022
Volume : 170
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Wolbachia are maternally transmitted intracellular bacteria that are not only restricted to the reproductive organs but also found in various somatic tissues of their native hosts. The abundance of the endosymbiont in the soma, usually a dead end for vertically transmitted bacteria, causes a multitude of effects on life history traits of their hosts, which are still not well understood. Thus, deciphering the host-symbiont interactions on a cellular level throughout a host’s life cycle is of great importance to understand their homeostatic nature, persistence, and spreading success. Using fluorescent and transmission electron microscopy, we conducted a comprehensive analysis of Wolbachia tropism in soma and germ line of six Drosophila species at the intracellular level during host development. Our data uncovered diagnostic patterns of infections to embryonic primordial germ cells and to particular cells of the soma in three different neotropical Drosophila species that have apparently evolved independently. We further found that restricted patterns of Wolbachia tropism are determined in early embryogenesis via selective autophagy, and their spatially restricted infection patterns are preserved in adult flies. We observed tight interactions of Wolbachia with membranes of the endoplasmic reticulum, which might play a scaffolding role for autophagosome formation and subsequent elimination of the endosymbiont. Finally, by analyzing D. simulans lines transinfected with nonnative Wolbachia, we uncovered that the host genetic background regulates tissue tropism of infection. Our data demonstrate a novel and peculiar mechanism to limit and spatially restrict bacterial infection in the soma during a very early stage of host development.
Auteurs, date et publication :
Auteurs Anton Strunov , Katy Schmidt , Martin Kapun , Wolfgang J. Miller , Bruno Lemaitre
Publication : mBio
Date : 2022
Volume : 13
Issue : 2
Pages : e03863-21
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Major historical landscape changes have left significant signatures on species diversification. However, how these changes have affected the build-up and maintenance of Amazonia's megadiversity continues to be debated. Here, we addressed this issue by focusing on the evolutionary history of a pan-Amazonian toad genus that has diversified throughout the Neogene (Amazophrynella). Based on a comprehensive spatial and taxonomic sampling (286 samples, all nominal species), we delimited operational taxonomic units (OTUs) from mitochondrial DNA sequences. We delimited 35 OTUs, among which 13 correspond to nominal species, suggesting a vast underestimation of species richness. Next, we inferred time-calibrated phylogenetic relationships among OTUs based on complete mitogenomic data, which confirmed an ancient divergence between two major clades distributed in eastern and western Amazonia, respectively. Ancestral area reconstruction analyses suggest that the Andean foothills and the Brazilian Shield region represent the ancient core areas for their diversification. These two clades, probably isolated from one other by lacustrine ecosystems in western Amazonia during the Miocene, display a pattern of northward and eastward dispersals throughout the Miocene-Pliocene. Given the ecological association of Amazophrynella with non-flooded forests, our results reinforce the perception that ancient Amazonian landscape changes had a major impact on the diversification of terrestrial vertebrates.
Auteurs, date et publication :
Auteurs Leandro J. C. L. Moraes , Fernanda P. Werneck , Alexandre Rejaud , Miguel T. Rodrigues , Ivan Prates , Frank Glaw , Philippe J. R. Kok , Santiago R. Ron , Juan C. Chaparro , Mariela Osorno-Munoz , Francisco Dal Vechio , Renato S. Recoder , Sergio Marques-Souza , Rommel R. Rojas , Lea Demay , Tomas Hrbek , Antoine Fouquet
Publication : BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY
Date : 2022
Volume : 136
Issue : 1
Pages : 75-91
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Isabelle Braud , Chloé Martin , Isabelle Charpentier , Jean-François Le Gaillard
Date : 2022
Catégorie(s)
#CNRS #Ecotron IleDeFrance #ENSRésumé
The occurrence and distribution of the various species of the genus Pelecocera Meigen, 1822 (Diptera: Syrphidae) occurring in France are revised and a new species, Pelecocera garrigae Lair & Nève, 2022 sp. nov., is described from Mediterranean France. Distribution and ecological data of the six French species of Pelecocera are provided and an identification key is given to all these species. Sequences of the cytochrome c oxidase subunit I (COI) from all European Pelecocera species support the morphological species concept, except for Pelecocera scaevoides (Fallén, 1817). The binomen Pelecocera lugubris Perris, 1839 is recovered to name the Pelecocera lusitanica (Mik, 1898) of authors in France.
Auteurs, date et publication :
Auteurs Xavier Lair , Lise Ropars , Jeffrey H. Skevington , Scott Kelso , Benoît Geslin , Elise Minssieux , Gabriel Nève
Publication : Zootaxa
Date : 2022
Volume : 5141
Issue : 1
Pages : 1-24