Résumé
Abstract
Loss in intraspecific diversity can alter ecosystem functions, but the underlying mechanisms are still elusive, and intraspecific biodiversity-ecosystem function relationships (iBEF) have been restrained to primary producers. Here, we manipulated genetic and functional richness of a fish consumer (Phoxinus phoxinus), to test whether iBEF relationships exist in consumer species, and whether they are more likely sustained by genetic or functional richness. We found that both genotypic and functional richness affected ecosystem functioning, either independently or in interaction. Loss in genotypic richness reduced benthic invertebrate diversity consistently across functional richness treatments, whereas it reduced zooplankton diversity only when functional richness was high. Finally, both losses in genotypic and functional richness altered essential functions (e.g. decomposition) through trophic cascades. We concluded that iBEF relationships lead to substantial top-down effects on entire food chains. The loss of genotypic richness impacted ecological properties as much as the loss of functional richness, probably because it sustains “cryptic” functional diversity.
Auteurs, date et publication :
Auteurs Allan Raffard , Julien Cucherousset , José M. Montoya , Murielle Richard , Samson Acoca-Pidolle , Camille Poésy , Alexandre Garreau , Frédéric Santoul , Simon Blanchet
Publication : bioRxiv
Date : 2020
Pages : 2020.06.10.144337
Catégorie(s)
#CNRS #Metatron aquatiqueAuteurs, date et publication :
Auteurs Aurélie Lacoeuilhe , Katia Hérard , Laurent Poncet , Julien Touroult
Publication : PatriNat (OFB-MNHN-CNRS-IRD)
Date : 2025
Pages : 52
Catégorie(s)
#⛔ No DOI found #CNRS #FORET NouraguesRésumé
Responses of ecosystems to modifications of their environmental conditions are usually considered in terms of biodiversity or function. Maybe because they represent a hidden part of ecosystems, responses of ecological interactions are rarely studied. A more comprehensive view of the processes underlying the restructuring of food webs under environmental gradients appears crucial to understand how ecosystems functionalities are altered. We address this general issue in an experiment where trophic interactions are reorganized under a gradient of top–down effects (predation pressure) and bottom–up effects (nutrient availability). Unimodal relationships of species diversity are pervasive in ecology; we extend this principle to food-web topology: in our study, most topological descriptor values peak at intermediate predation intensity. The same unimodal pattern holds for network complexity, measured by entropy and scaled entropy (a measure independent of species diversity). Moreover, food web complexity is maximized at higher fish abundance when nutrient availability is increased. We infer that whereas in absence of top predators, a mechanism of competitive exclusion takes place, and indirect facilitation process underlies systems with a moderate predation pressure. These results highlight the importance of the dynamic reorganization of trophic links in response to bottom–up and top–down effects. Interaction between bottom–up and top–down forces argue for multifactorial studies of ecological effects.
Auteurs, date et publication :
Auteurs Benoit Gauzens , Stéphane Legendre , Xavier Lazzaro , Gérard Lacroix
Publication : Oikos
Date : 2016
Volume : 125
Issue : 4
Pages : 595-603
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
Runt-related transcription factor 1 (RUNX1) is a well-known master regulator of hematopoietic lineages but its mechanisms of action are still not fully understood. Here, we found that RUNX1 localizes on active chromatin together with Far Upstream Binding Protein 1 (FUBP1) in human B-cell precursor lymphoblasts, and that both factors interact in the same transcriptional regulatory complex. RUNX1 and FUBP1 chromatin localization identified c-KIT as a common target gene. We characterized two regulatory regions, at +700 bp and +30 kb within the first intron of c-KIT, bound by both RUNX1 and FUBP1, and that present active histone marks. Based on these regions, we proposed a novel FUBP1 FUSE-like DNA-binding sequence on the +30 kb enhancer. We demonstrated that FUBP1 and RUNX1 cooperate for the regulation of the expression of the oncogene c-KIT. Notably, upregulation of c-KIT expression by FUBP1 and RUNX1 promotes cell proliferation and renders cells more resistant to the c-KIT inhibitor imatinib mesylate, a common therapeutic drug. These results reveal a new mechanism of action of RUNX1 that implicates FUBP1, as a facilitator, to trigger transcriptional regulation of c-KIT and to regulate cell proliferation. Deregulation of this regulatory mechanism may explain some oncogenic function of RUNX1 and FUBP1.
Auteurs, date et publication :
Auteurs Lydie Debaize , Hélène Jakobczyk , Stéphane Avner , Jérémie Gaudichon , Anne-Gaëlle Rio , Aurélien A Sérandour , Lena Dorsheimer , Frédéric Chalmel , Jason S Carroll , Martin Zörnig , Michael A Rieger , Olivier Delalande , Gilles Salbert , Marie-Dominique Galibert , Virginie Gandemer , Marie-Bérengère Troadec
Publication : Nucleic Acids Research
Date : 2018
Volume : 46
Issue : 21
Pages : 11214-11228
Catégorie(s)
#CNRS #EcoGenO #Université de RennesRésumé
Rock glaciers are creeping bodies of ice and rock that account for an important part of the mountain cryosphere. In this study, we investigated long-term changes of the Laurichard rock glacier (French Alps), to understand how this rock glacier is responding to climate change. Using feature-tracking and photogrammetric measurements between 1952 and 2019, we quantified changes in thickness, flow velocities and from which we derived the ice/rock flux of the rock glacier at a decadal time scale. This is the first time that emergence velocity and surface mass balance changes have been reconstructed for a rock glacier. Our results reveal a very small surface mass balance ranging from −0.1 m a−1 to +0.05 m a−1, reflecting the role of debris in damping the melt rate of the underlying ice. Surprisingly, we found a more negative surface mass balance in the upper part than in the lower part of the rock glacier during the 1952–1971 cold period, likely due to a reduction in rock and snow mass accumulation. Our study shows that thickness changes are mainly driven by changes in surface mass balance except during the most recent period in the lower part of the rock glacier, which was also influenced by a compressive flow related to a protrusion that prevented the rock glacier from advancing. We conclude that the period 1994–2019 witnessed a marked acceleration in rock glacier flow, in agreement with the observations of other rock glaciers in the European Alps. This strong increase in surface speed is likely a consequence of changes in the basal conditions.
Auteurs, date et publication :
Auteurs Diego Cusicanqui , Antoine Rabatel , Christian Vincent , Xavier Bodin , Emmanuel Thibert , Bernard Francou
Publication : Journal of Geophysical Research: Earth Surface
Date : 2025
Volume : 126
Issue : 9
Pages : e2021JF006161
Catégorie(s)
#CNRS #Lautaret #UGARésumé
Plant phenological development is orchestrated through subtle changes in photoperiod, temperature, soil moisture and nutrient availability. Presently, the exact timing of plant development stages and their response to climate and management practices are crudely represented in land surface models. As visual observations of phenology are laborious, there is a need to supplement long-term observations with automated techniques such as those provided by digital repeat photography at high temporal and spatial resolution. We present the first synthesis from a growing observational network of digital cameras installed on towers across Europe above deciduous and evergreen forests, grasslands and croplands, where vegetation and atmosphere CO2 fluxes are measured continuously. Using colour indices from digital images and using piecewise regression analysis of time series, we explored whether key changes in canopy phenology could be detected automatically across different land use types in the network. The piecewise regression approach could capture the start and end of the growing season, in addition to identifying striking changes in colour signals caused by flowering and management practices such as mowing. Exploring the dates of green-up and senescence of deciduous forests extracted by the piecewise regression approach against dates estimated from visual observations, we found that these phenological events could be detected adequately (RMSE < 8 and 11 days for leaf out and leaf fall, respectively). We also investigated whether the seasonal patterns of red, green and blue colour fractions derived from digital images could be modelled mechanistically using the PROSAIL model parameterised with information of seasonal changes in canopy leaf area and leaf chlorophyll and carotenoid concentrations. From a model sensitivity analysis we found that variations in colour fractions, and in particular the late spring ‘green hump’ observed repeatedly in deciduous broadleaf canopies across the network, are essentially dominated by changes in the respective pigment concentrations. Using the model we were able to explain why this spring maximum in green signal is often observed out of phase with the maximum period of canopy photosynthesis in ecosystems across Europe. Coupling such quasi-continuous digital records of canopy colours with co-located CO2 flux measurements will improve our understanding of how changes in growing season length are likely to shape the capacity of European ecosystems to sequester CO2 in the future.
Auteurs, date et publication :
Auteurs L Wingate , J Ogée , E Cremonese , G Filippa , T Mizunuma , M Migliavacca , C Moisy , M Wilkinson , C Moureaux , G Wohlfahrt , A Hammerle , L Hörtnagl , C Gimeno , A Porcar-Castell , M Galvagno , T Nakaji , J Morison , O Kolle , A Knohl , W Kutsch
Publication : Biogeosciences
Date : 2025
Volume : 12
Pages : 5995-6015
Catégorie(s)
#ACBB #ACBB Theix #CNRS #FORET PuechabonRésumé
Annual plants usually flower and set seed once before senescence results in the death of the whole plant (monocarpic senescence). Leaf senescence also occurs in polycarpic perennials; even in “evergreen” species individual leaves senesce. In the annual model Arabidopsis thaliana sugars accumulate in the senescent leaves and senescence is accelerated by high sugar availability. Similar to A. thaliana, sugar contents increased with leaf age in the perennial Arabis alpina grown under warm conditions (22 ◦C day/18 night). At 5 ◦C, sugar contents in non-senescent leaves were higher than at a warm temperature, but dependent on the accession, either sugars did not accumulate or their contents decreased in old leaves. In A. alpina plants grown in their natural habitat in the Alps, sugar contents declined with leaf age. Growth at a cold temperature slightly delayed senescence in A. alpina. In both warm and cold conditions, an external glucose supply accelerated senescence, but natural variation was found in this response. In conclusion, sugar accumulation under warm conditions could accelerate leaf senescence in A. alpina plants, but genotype-specific responses and interactions with growth temperature are likely to influence senescence under natural conditions.
Auteurs, date et publication :
Auteurs Astrid Wingler , Emma Josefine Stangberg , Triambak Saxena , Rupal Mistry
Publication : Journal of Integrative Plant Biology
Date : 2025
Volume : 54
Issue : 8
Pages : 595-605
Catégorie(s)
#CNRS #Lautaret #UGAAuteurs, date et publication :
Auteurs Kejun Zou , Elisa Thébault , Gérard Lacroix , Sébastien Barot , Shawn Leroux
Publication : Functional Ecology
Date : 2025
Volume : 30
Issue : 8
Pages : 1454-1465
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
Soil organisms play a key role in carbon and nutrient cycling in forest ecosystems. While soil organisms are strongly influenced by litter chemistry and are highly sensitive to abiotic conditions, little is known about the interactive effects of these two factors. To address this gap in knowledge, we conducted a 10 week microcosm experiment in which we simulated the effects of climate change on soil ecology. More specifically, we studied relationships among litter nutrient concentration, microbial biomass, Collembola demographic parameters, and litter decomposition, exploring the potential impacts of increasing air temperature and decreasing soil moisture. To develop a gradient of nutrient concentrations, we created six tree litter mixtures with materials gathered from Quercus pubescens and its companion species. In contrast to microbes, we observed that Collembola abundance and litter decomposition were interactively affected by soil moisture and air temperature: the negative effect of increasing air temperature on Collembola abundance was amplified by reduced soil moisture, whereas the positive effect of increasing air temperature on litter decomposition disappeared under reduced soil moisture conditions. In contrast to fungi, the response of bacterial biomass and Collembola abundance to litter nutrient concentration was dependent on abiotic conditions. More specifically, the relationships between nutrients, especially calcium and magnesium, and bacterial biomass and Collembola abundance were less robust or disappeared under drier or warmer conditions. In conclusion, our findings underscore that ongoing climate change could affect soil organisms directly as well as indirectly, by altering their responses to litter nutrient concentrations. In addition, we found that nutrient-rich habitats might be more affected than nutrient-poor habitats by altered climatic conditions.
Auteurs, date et publication :
Auteurs Charlotte Biryol , Adriane Aupic-Samain , Caroline Lecareux , Thierry Gauquelin , Virginie Baldy , Mathieu Santonja
Publication : OIKOS
Date : 2024
Volume : 2024
Issue : 7
Catégorie(s)
#ANR-Citation #CNRS #FORET O3HPRésumé
The accumulation of studies delimiting species in Amazonia has not only shed light on the patterns of its outstanding species richness but also allowed a better understanding of the processes of diversification within this immense region. Nevertheless, vast knowledge gaps remain even for prominent anuran species complexes, such as the Rhinella margaritifera species group. This clade of toads comprises 23 valid species-level taxa, mainly distributed in Amazonia but also in South America's Dry Diagonal and Atlantic and trans-Andean rainforests. Species boundaries and taxonomy in this group are notoriously complex, with studies suggesting the existence of several unnamed species. Available phylogenetic information suggests an Andean-western Amazonian origin of the group with subsequent diversification within Amazonian lowlands during the last 10 Myr and secondary dispersals into other Neotropical regions. To further test this biogeographic scenario and improve knowledge on species diversity, we used an unprecedentedly large mtDNA sampling (>800 16S sequences) across the clade's distribution and comprising all but one described species. We delimited 54 Molecular Operational Taxonomic Units, which we tested further based on patterns of variation of a nuclear locus and acoustic and morphological data. This approach confirmed the existence of at least 25 candidate species, 19 of which correspond to currently recognized taxa whereas 30 remained `unconfirmed'. Our results clarify the taxonomic status of some species but also suggest multiple introgression events that blur some mtDNA-based species boundaries. Lastly, to provide a temporal framework for the clade's diversification, we generated a time-calibrated phylogenetic tree based on a mitogenomic matrix, which confirmed a Miocene (similar to 9 Ma) western Amazonian origin and six major clades in the group, each having initially diversified in different regions within Amazonia. Most of these clades have later dispersed throughout Amazonia during the establishment of the modern Amazonian hydrographic system, i.e., in the last 6 Myr.
Auteurs, date et publication :
Auteurs Antoine Fouquet , Miqueias Ferrao , Miguel T. Rodrigues , Fernanda P. Werneck , Ivan Prates , Leandro J. C. L. Moraes , Tomas Hrbek , Juan C. Chaparro , Albertina P. Lima , Renata Perez , Andre Pansonato , Vinicius T. Carvalho , Alexandre P. Almeida , Marcelo Gordo , Izeni P. Farias , Konstantin D. Milto , Igor J. Roberto , Rommel R. Rojas , Santiago R. Ron , Vinicius Guerra
Publication : SYSTEMATICS AND BIODIVERSITY
Date : 2024
Volume : 22
Issue : 1