Résumé
Phenotypic effects of global warming have been documented in many different taxa. However, the importance of transgenerational phenotypic plasticity in these adaptations are seldom studied. In birds, temperature could affect egg characteristics. Higher temperatures during egg-laying may reduce maintenance costs for females and allow a higher investment in reproduction. Yet, females may also use temperatures as a cue for the risk of mismatch latter in the season. Thus, higher temperatures may be correlated to an acceleration of embryonic development (e.g. via hormonal manipulation). We performed an experiment in which night-time temperature was increased in the nestbox by approximately 1 degrees C throughout the entire laying period in great tits (Parus major). We collected one pre-treatment egg (beginning of the laying sequence) and one post-treatment egg (end of the laying sequence). Egg content (yolk androgens and lysozymes in the albumen), eggshell coloration, eggshell mass, egg mass, and shape were not affected by the treatment. However, last-laid eggs in clutches from control nestboxes had a thicker eggshell than last-laid eggs from heated nestboxes, suggesting a putative slight decrease of maternal investment with the experimental increase of temperature. We also observed effects of the laying sequence on egg characteristics. Eggs that were laid late in the laying sequence were heavier, larger, had larger spots and higher yolk androgens than eggs laid earlier. Lysozyme concentration decrease with the laying sequence in late clutches only. Thus, effects of temperature may also change with the laying sequence and it would be interesting in the future to tests the effects on first-laid eggs.
Auteurs, date et publication :
Auteurs Josefa Bleu , Simon Agostini , Frederic Angelier , Clotilde Biard
Publication : GENERAL AND COMPARATIVE ENDOCRINOLOGY
Date : 2019
Volume : 275
Pages : 73-81
Catégorie(s)
#ANR-Citation #CEREEP #CNRS #ENSRésumé
The primary objective of the European Space Agency's 7th Earth Explorer mission, BIOMASS, is to determine the worldwide distribution of forest above-ground biomass (AGB) in order to reduce the major uncertainties in calculations of carbon stocks and fluxes associated with the terrestrial biosphere, including carbon fluxes associated with Land Use Change, forest degradation and forest regrowth. To meet this objective it will carry, for the first time in space, a fully polarimetric P-band synthetic aperture radar (SAR). Three main products will be provided: global maps of both AGB and forest height, with a spatial resolution of 200 m, and maps of severe forest disturbance at 50 m resolution (where “global” is to be understood as subject to Space Object tracking radar restrictions). After launch in 2022, there will be a 3-month commissioning phase, followed by a 14-month phase during which there will be global coverage by SAR tomography. In the succeeding interferometric phase, global polarimetric interferometry Pol-InSAR coverage will be achieved every 7 months up to the end of the 5-year mission. Both Pol-InSAR and TomoSAR will be used to eliminate scattering from the ground (both direct and double bounce backscatter) in forests. In dense tropical forests AGB can then be estimated from the remaining volume scattering using non-linear inversion of a backscattering model. Airborne campaigns in the tropics also indicate that AGB is highly correlated with the backscatter from around 30 m above the ground, as measured by tomography. In contrast, double bounce scattering appears to carry important information about the AGB of boreal forests, so ground cancellation may not be appropriate and the best approach for such forests remains to be finalized. Several methods to exploit these new data in carbon cycle calculations have already been demonstrated. In addition, major mutual gains will be made by combining BIOMASS data with data from other missions that will measure forest biomass, structure, height and change, including the NASA Global Ecosystem Dynamics Investigation lidar deployed on the International Space Station after its launch in December 2018, and the NASA-ISRO NISAR L- and S-band SAR, due for launch in 2022. More generally, space-based measurements of biomass are a core component of a carbon cycle observation and modelling strategy developed by the Group on Earth Observations. Secondary objectives of the mission include imaging of sub-surface geological structures in arid environments, generation of a true Digital Terrain Model without biases caused by forest cover, and measurement of glacier and icesheet velocities. In addition, the operations needed for ionospheric correction of the data will allow very sensitive estimates of ionospheric Total Electron Content and its changes along the dawn-dusk orbit of the mission.
Auteurs, date et publication :
Auteurs Shaun Quegan , Thuy Le Toan , Jerome Chave , Jorgen Dall , Jean-François Exbrayat , Dinh Ho Tong Minh , Mark Lomas , Mauro Mariotti D'Alessandro , Philippe Paillou , Kostas Papathanassiou , Fabio Rocca , Sassan Saatchi , Klaus Scipal , Hank Shugart , T. Luke Smallman , Maciej J. Soja , Stefano Tebaldini , Lars Ulander , Ludovic Villard , Mathew Williams
Publication : Remote Sensing of Environment
Date : 2019
Volume : 227
Pages : 44-60
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Synthetic aperture radar (SAR) tomography (TomoSAR) is an emerging technology to image the 3D structure of the illuminated media. TomoSAR exploits the key feature of microwaves to penetrate into vegetation, snow, and ice, hence providing the possibility to see features that are hidden to optical and hyper-spectral systems. The research on the use of P-band waves, in particular, has been largely propelled since 2007 in experimental studies supporting the future spaceborne Mission BIOMASS, to be launched in 2022 with the aim of mapping forest aboveground biomass (AGB) accurately and globally. The results obtained in the frame of these studies demonstrated that TomoSAR can be used for accurate retrieval of geophysical variables such as forest height and terrain topography and, especially in the case of dense tropical forests, to provide a more direct link to AGB. This paper aims at providing the reader with a comprehensive understanding of TomoSAR and its application for remote sensing of forested areas, with special attention to the case of tropical forests. We will introduce the basic physical principles behind TomoSAR, present the most relevant experimental results of the last decade, and discuss the potentials of BIOMASS tomography.
Auteurs, date et publication :
Auteurs Stefano Tebaldini , Dinh Ho Tong Minh , Mauro Mariotti d’Alessandro , Ludovic Villard , Thuy Le Toan , Jerome Chave
Publication : Surveys in Geophysics
Date : 2019
Volume : 40
Issue : 4
Pages : 779-801
Catégorie(s)
#CIRAD #CNRS #FORET Nouragues #FORET ParacouRésumé
Studying variation in life-history traits and correlated behaviours, such as boldness and foraging (i.e., pace-of-life syndrome), allows us to better understand how these traits evolve in a changing environment. In fish, it is particularly relevant studying the interplay of resource abundance and size-selection. These are two environmental stressors affecting fish in natural conditions, but also associated with human-induced environmental change. For instance, fishing, one of the most important threats for freshwater and marine populations, results in both higher mortality on large-sized fish and reduced population density.
Auteurs, date et publication :
Auteurs Beatriz Diaz Pauli , Sarah Garric , Charlotte Evangelista , L. Asbjørn Vøllestad , Eric Edeline
Publication : BMC Evolutionary Biology
Date : 2019
Volume : 19
Issue : 1
Pages : 127
Catégorie(s)
#CNRS #ENS #PLANAQUARésumé
Changes in terrestrial tropical carbon stocks have an important role in the global carbon budget. However, current observational tools do not allow accurate and large-scale monitoring of the spatial distribution and dynamics of carbon stocks'. Here, we used low-frequency L-band passive microwave observations to compute a direct and spatially explicit quantification of annual aboveground carbon (AGC) fluxes and show that the tropical net AGC budget was approximately in balance during 2010 to 2017, the net budget being composed of gross losses of -2.86 PgC yr(-1) offset by gross gains of -2.97 PgC yr(-1) between continents. Large interannual and spatial fluctuations of tropical AGC were quantified during the wet 2011 La Nina year and throughout the extreme dry and warm 2015-2016 El Nino episode. These interannual fluctuations, controlled predominantly by semiarid biomes, were shown to be closely related to independent global atmospheric CO2 growth-rate anomalies (Pearson's r = 0.86), highlighting the pivotal role of tropical AGC in the global carbon budget.
Auteurs, date et publication :
Auteurs Lei Fan , Jean-Pierre Wigneron , Philippe Ciais , Jerome Chave , Martin Brandt , Rasmus Fensholt , Sassan S. Saatchi , Ana Bastos , Amen Al-Yaari , Koen Hufkens , Yuanwei Qin , Xiangming Xiao , Chi Chen , Ranga B. Myneni , Roberto Fernandez-Moran , Arnaud Mialon , N. J. Rodriguez-Fernandez , Yann Kerr , Feng Tian , Josep Penuelas
Publication : NATURE PLANTS
Date : 2019
Volume : 5
Issue : 9
Pages : 944-951
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Continental relative humidity (RH) is a key climate parameter, but there is a lack of quantitative RH proxies suitable for climate model-data comparisons. Recently, a combination of climate chamber and natural transect calibrations have laid the groundwork for examining the robustness of the triple oxygen isotope composition (delta O-'18 and O-17-excess) of phytoliths, that can preserve in sediments, as a new proxy for past changes in RH. However, it was recommended that besides RH, additional factors that may impact delta'O-18 and O-17-excess of plant water and phytoliths be examined. Here, the effects of grass leaf length, leaf development stage and day-night alternations are addressed from growth chamber experiments. The triple oxygen isotope compositions of leaf water and phytoliths of the grass species F. arundinacea are analysed. Evolution of the leaf water delta'O-18 and O-17-excess along the leaf length can be modelled using a string-of-lakes approach to which an unevaporated-evaporated mixing equation must be added. We show that for phytoliths to record this evolution, a kinetic fractionation between leaf water and silica, increasing from the base to the apex, must be assumed. Despite the isotope heterogeneity of leaf water along the leaf length, the bulk leaf phytolith delta'O-18 and O-17-excess values can be estimated from the Craig and Gordon model and a mean leaf water-phytolith fractionation exponent (lambda(Phyto-LW)) of 0.521. In addition to not being leaf length dependent, delta'O-18 and O-17-excess of grass phytoliths are expected to be impacted only very slightly by the stem vs. leaf biomass ratio. Our experiment additionally shows that because a lot of silica polymerises in grasses when the leaf reaches senescence (58 % of leaf phytoliths in mass), RH prevailing during the start of senescence should be considered in addition to RH prevailing during leaf growth when interpreting the O-17-excess of grass bulk phytoliths. Although under the study conditions O-17-excess(Phyto) do not vary significantly from constant day to day-night conditions, additional monitoring at low RH conditions should be done before drawing any generalisable conclusions. Overall, this study strengthens the reliability of the O-17-excess of phytoliths to be used as a proxy of RH. If future studies show that the mean value of 0.521 used for the grass leaf water-phytolith fractionation exponent lambda(Phyto-LW) is not climate dependent, then grassland leaf water O-17-excess obtained from grassland phytolith O-17-excess would inform on isotope signals of several soil-plant-atmosphere processes.
Auteurs, date et publication :
Auteurs Anne Alexandre , Elizabeth Webb , Amaelle Landais , Clement Piel , Sebastien Devidal , Corinne Sonzogni , Martine Couapel , Jean-Charles Mazur , Monique Pierre , Frederic Prie , Christine Vallet-Coulomb , Clement Outrequin , Jacques Roy
Publication : BIOGEOSCIENCES
Date : 2019
Volume : 16
Issue : 23
Pages : 4613-4625
Catégorie(s)
#ANR-Citation #CNRS #Ecotron de MontpellierRésumé
Prolonged and complex courtship behaviors, involving tactile, acoustic, and visual signals, are common in Neotropical poison frogs (Dendrobatidae). Courtship is an important precursor to mating, but courtship components vary across species. In Brilliant-Thighed Poison Frogs (Allobates femorlis [Boulanger 1883]), males guide females to oviposition sites in a so-called “courtship march.” The courtship duration in A. femorlis is among the longest known in poison frogs. To gain insights into the functions of courtship, we observed 29 courtship events in an A. femorlis population in French Guiana. In addition, we observed multiple courtships of 7 males to assess intra- and interindividual variations in courtship behavior. We recorded temporal, spatial, and behavioral characteristics of courtship and searched for previously deposited clutches in the males' territories. Courtships started in the afternoon and ended on the following morning. During courtship, pairs moved an average of 19 m within an area of about 6 m(2). Twenty-seven out of 29 courtships (93.1%) resulted in successful oviposition, indicating that females rarely reject males once engaged in courtship. Contrary to previous studies of A. femoralis, the spatial and temporal extent of the courtship march did not correlate with the size of a male's territory. Our results indicate that females do not evaluate male quality during courtship but might need an extended courtship phase to verify territory ownership of the courting male and to stimulate ovulation. The prolonged courtship might also be beneficial for spatial learning by females, allowing them to find clutches again in cases of mate loss. Temporal and spatial characteristics vary considerably within and among individuals, and males do not use the same routes in consecutive courtships. However, they probably show females previous clutches. Several courtship traits in our study population differ from A. femoralis courtship previously described from Peru and Brazil, indicating that dendrobatid courtship is variable among populations.
Auteurs, date et publication :
Auteurs Susanna Stueckler , Max Ringler , Andrius Pasukonis , Steffen Weinlein , Walter Hoedl , Eva Ringler
Publication : HERPETOLOGICA
Date : 2019
Volume : 75
Issue : 4
Pages : 268-279
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesAuteurs, date et publication :
Auteurs Sruthi M Krishna Moorthy , Pasi Raumonen , Jan Van den Bulcke , Kim Calders , Hans Verbeeck
Publication : Forest Ecology and Management
Date : 2025
Volume : 456
Pages : 117751
Catégorie(s)
#CNRS #FORET NouraguesRésumé
Leaf-inhabiting fungal and bacterial endophytes are at their most diverse in tropical rainforest plant hosts, with some influencing host plant fitness as either symbionts or pathogens. Endophyte activity and community composition is thought to depend on competition amongst co-occurring species for resources. Here, we reveal the strength of competitive interactions between endophytes by combining e-DNA metabarcoding to characterize the community with culturing assays to ascertain their potential activity. The endophyte community associated with the understory palm Astrocaryum sciophilum was determined by extracting eDNA from 120 leaflets of eight plants located in a lowland rainforest in French Guiana. This revealed 516 fungal and 606 bacterial Operational Taxonomic Units (OTUs). Co-occurrence analysis of the most abundant OTUs revealed that direct fungal-fungal interactions were overall more negative than bacterial-bacterial interactions. This was confirmed by C-score calculations for the whole endophyte community, revealing significantly greater levels of species segregation for fungi but not bacteria when compared with simulated random communities. Following the culturing of 131 fungal, and 66 bacterial Astrocaryum endophytes collected from the same leaves, Minimal Inhibitory Concentrations of ethyl acetate culture extracts were evaluated against the fungus Trichophyton rubrum and the bacterium Staphylococcus aureus. Overall, a minority of extracts demonstrated antipathogen activity, with greater antifungal activity expression for both fungi and bacteria when compared with antibacterial activity. In order to explore whether this activity translated into competitive structuring of the community, a BLAST was conducted to match metabarcoding sequences with Sanger derived culture sequences. This demonstrated that cultures displaying antipathogen activity were significantly more likely to co-occur with fungi if they were bacteria, and bacteria if they were fungi. Nevertheless, overall correlation values averaged around zero. These results indicate that for Astrocaryum palms, fungal endophytes are likely to play a greater role in determining colonization success of subsequent endophytes whether these be fungal or bacterial, but that overall endophyte communities do not display strong patterns of community structuring through competition. Endophyte communities are thus likely to reach relative stasis in mature leaves, where the diverse community of fungi and bacteria amongst other factors prevent the subsequent establishment of pathogens.
Auteurs, date et publication :
Auteurs Julian Donald , Morgane Barthelemy , Nina Gazal , Yannick Eveno , Sophie Manzi , Veronique Eparvier , Didier Stien , Melanie Roy
Publication : FRONTIERS IN FORESTS AND GLOBAL CHANGE
Date : 2019
Volume : 2
Catégorie(s)
#ANR-Citation #CNRS #FORET NouraguesRésumé
Anthropogenic perturbations such as harvesting often select against a large body size and are predicted to induce rapid evolution toward smaller body sizes and earlier maturation. However, body-size evolvability and, hence, adaptability to anthropogenic perturbations remain seldom evaluated in wild populations. Here, we use a laboratory experiment over 6 generations to measure the ability of wild-caught medaka fish (Oryzias latipes) to evolve in response to bidirectional size-dependent selection mimicking opposite harvest regimes. Specifically, we imposed selection against a small body size (Large line), against a large body size (Small line) or random selection (Control line), and measured correlated responses across multiple phenotypic, life-history, and endocrine traits. As expected, the Large line evolved faster somatic growth and delayed maturation, but also evolved smaller body sizes at hatch, with no change in average levels of pituitary gene expressions of luteinizing, follicle-stimulating, or growth hormones (GH). In contrast, the Small medaka line was unable to evolve smaller body sizes or earlier maturation, but evolved smaller body sizes at hatch and showed marginally significant signs of increased reproductive investment, including larger egg sizes and elevated pituitary GH production. Natural selection on medaka body size was too weak to significantly hinder the effect of artificial selection, indicating that the asymmetric body-size response to size-dependent selection reflected an asymmetry in body-size evolvability. Our results show that trait evolvability may be contingent upon the direction of selection and that a detailed knowledge of trait evolutionary potential is needed to forecast population response to anthropogenic change.
Auteurs, date et publication :
Auteurs Clémentine Renneville , Alexis Millot , Simon Agostini , David Carmignac , Gersende Maugars , Sylvie Dufour , Arnaud Le Rouzic , Eric Edeline
Publication : Ecology and Evolution
Date : 2025
Volume : 10
Issue : 19
Pages : 10571-10592