Résumé
In this study, conducted in French Guiana, a part of the native range of the fire ant Solenopsis saevissima, we compared the cuticular hydrocarbon profiles of media workers with previous results based on intraspecific aggressiveness tests. We noted a strong congruence between the two studies permitting us to delimit 2 supercolonies extending over large distances (up to 54 km), a phenomenon known as unicoloniality. Solenopsis geminata workers, taken as an out‐group for cluster analyses, have a very different cuticular hydrocarbon profile. Because S. saevissima has been reported outside its native range, our conclusion is that this species has the potential to become invasive because unicoloniality (i.e., the main attribute for ants to become invasive) was shown at least for the Guianese population.
Auteurs, date et publication :
Auteurs Alain Lenoir , Séverine Devers , Axel Touchard , Alain Dejean
Publication : Insect Science
Date : 2016
Volume : 23
Issue : 5
Pages : 739–745
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Clément Stahl , Vincent Freycon , Sébastien Fontaine , Camille Dezécache , Lise Ponchant , Catherine Picon-Cochard , Katja Klumpp , Jean-François Soussana , Vincent Blanfort
Publication : Regional Environmental Change
Date : 2016
Volume : 16
Issue : 7
Pages : 2059–2069
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Although bats are natural reservoirs of many pathogens, few studies have been conducted on the genetic variation and detection of selection in major histocompatibility complex (MHC) genes. These genes are critical for resistance and susceptibility to diseases, and host–pathogen interactions are major determinants of their extensive polymorphism. Here we examined spatial patterns of diversity of the expressed MHC class II DRB gene of three sympatric Neotropical bats, Carollia perspicillata and Desmodus rotundus (Phyllostomidae), and Molossus molossus (Molossidae), all of which use the same environments (e.g., forests, edge habitats, urban areas). Comparison with neutral marker (mtDNA D-loop) diversity was performed at the same time. Twenty-three DRB alleles were identified in 19 C. perspicillata, 30 alleles in 35 D. rotundus and 20 alleles in 28 M. molossus. The occurrence of multiple DRB loci was found for the two Phyllostomidae species. The DRB polymorphism was high in all sampling sites and different signatures of positive selection were detected depending on the environment. The patterns of DRB diversity were similar to those of neutral markers for C. perspicillata and M. molossus. In contrast, these patterns were different for D. rotundus for which a geographical structure was highlighted. A heterozygote advantage was also identified for this species. No recombination or gene conversion event was found and phylogenetic relationships showed a trans-species mode of evolution in the Phyllostomids. This study of MHC diversity demonstrated the strength of the environment and contrasting pathogen pressures in shaping DRB diversity. Differences between positively selected sites identified in bat species highlighted the potential role of gut microbiota in shaping immune responses. Furthermore, multiple geographic origins and/or population admixtures observed in C. perspicillata and M. molossus populations acted as an additional force in shaping DRB diversity. In contrast, DRB diversity of D. rotundus was shaped by environment rather than demographic history.
Auteurs, date et publication :
Auteurs Arielle Salmier , Benoit de Thoisy , Brigitte Crouau-Roy , Vincent Lacoste , Anne Lavergne
Publication : BMC Evolutionary Biology
Date : 2016
Volume : 16
Issue : 1
Pages : 229
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Gérard Dubost, and Olivier Henry (2017) Seasonal changes in tropical forests have been documented in dry and semi-deciduous forests, but not in evergreen ones. Owing to its high level of annual rainfall, French Guiana is considered to be a rainy region, despite a pronounced dry season. French Guiana is therefore appropriate for studying the impact of the dry season on the phenology of rainforest animals. For this purpose, the reproductive characteristics of six terrestrial mammals of the French Guiana rainforest were studied during the four main seasons of the year. Reproduction was more or less continuous in both sexes of all species. Seasonality was not very pronounced and the species were not synchronised, except in terms of births. In all species, the minimum number of litters occurred between August and October. Furthermore, the seasonal birth percentages appeared to be linked to environmental factors such as rainfall and fruiting trees, and to diet as well: the more the diet of one species was composed of fruits, the more seasonal its litters were. Thus, like in many other regions worldwide, most births occur during the most favourable seasons for raising young in this rainforest. This signifies that even in this seemingly aseasonal region, the reproduction of mammals is mainly regulated by environmental factors at the time of birth.
Auteurs, date et publication :
Auteurs Gérard Dubost , Olivier Henry , Benny K K Chan
Publication : Zoological Studies
Date : 2025
Volume : 52
Issue : 2
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Odhran S. O'sullivan , Mary A. Heskel , Peter B. Reich , Mark G. Tjoelker , Lasantha K. Weerasinghe , Aurore Penillard , Lingling Zhu , John J. G. Egerton , Keith J. Bloomfield , Danielle Creek , Nur H. A. Bahar , Kevin L. Griffin , Vaughan Hurry , Patrick Meir , Matthew H. Turnbull , Owen K. Atkin
Publication : Global Change Biology
Date : 2017
Volume : 23
Issue : 1
Pages : 209–223
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Modern measures of diversity satisfy reasonable axioms, are parameterized to produce diversity profiles, can be expressed as an effective number of species to simplify their interpretation, and come with estimators that allow one to apply them to real-world data. We introduce the generalized Simpson's entropy as a measure of diversity and investigate its properties. We show that it has many useful features and can be used as a measure of biodiversity. Moreover, unlike most commonly used diversity indices, it has unbiased estimators, which allow for sound estimation of the diversity of poorly sampled, rich communities.
Auteurs, date et publication :
Auteurs Michael Grabchak , Eric Marcon , Gabriel Lang , Zhiyi Zhang , Stefan J. Green
Publication : Plos One
Date : 2017
Volume : 12
Issue : 3
Pages : e0173305
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Lucy Rowland , Joana Zaragoza-Castells , Keith J. Bloomfield , Matthew H. Turnbull , Damien Bonal , Benoit Burban , Norma Salinas , Eric Cosio , Daniel J. Metcalfe , Andrew Ford , Oliver L. Phillips , Owen K. Atkin , Patrick Meir
Publication : New Phytologist
Date : 2017
Volume : 214
Issue : 3
Pages : 1064–1077
Catégorie(s)
#CIRAD #FORET ParacouRésumé
Very high spatial resolution (VHSR) optical satellite imagery has shown good potential to provide non-saturating proxies of tropical forest aboveground biomass (AGB) from the analysis of canopy texture, for instance through the Fourier Transform Textural Ordination method. Empirical case studies however showed that the relationship between Fourier texture features and forest AGB varies across forest types and regions of the world, limiting model transferability. A better understanding of the biophysical mechanisms on which canopy texture – forest AGB relation relies is a prerequisite to move toward broad scale applications. Here we simulated VHSR optical canopy scenes in identical sun-sensor geometry for 279 1-ha tropical forest inventory plots distributed across the tropics. Our aim was to assess the respective merits and complementarity of two types of texture analysis techniques (i.e. Fourier and lacunarity) on a set of forests with contrasted structure and geographical origin, and develop a general texture-based approach for tropical forest AGB mapping. Across forests, Fourier texture captured a gradient of stands mean crown size reflecting well the progressive changes in stand structure throughout forest aggradation phase (e.g. Pearson's r=−0.42 with basal area) while lacunarity texture captured a gradient of canopy openness (, i.e. Pearson's r=−0.57 with stand gap fraction). Both types of texture indices were highly complementary for predicting forest AGB at the global level (so-called FL-model). The residual error of the FL-model was structured across sites and could be partially captured with a bioclimatic proxy, further improving the performance of the global model (so-called FLE-model) and reducing site-level biases. The FLE model was tested on a set of real Pleiades images covering a mosaic of high-biomass forests in the Congo basin (mean AGB over 49 field plots: 359±98Mgha−1), leading to a significant relationship (R2=0.47 on validation data) with reasonable error levels (textless25% rRMSE). The increasing availability of VHSR optical sensors (such as from constellations of small satellite platforms) raises the possibility of routine repeated imaging of the world's tropical forests and suggests that texture-based analyses could become an essential tool in international efforts to monitor carbon emissions from deforestation and forest degradations (REDD+).
Auteurs, date et publication :
Auteurs P. Ploton , N. Barbier , P. Couteron , C.M. Antin , N. Ayyappan , N. Balachandran , N. Barathan , J.-F. Bastin , G. Chuyong , G. Dauby , V. Droissart , J.-P. Gastellu-Etchegorry , N.G. Kamdem , D. Kenfack , M. Libalah , G. Mofack , S.T. Momo , S. Pargal , P. Petronelli , C. Proisy
Publication : Remote Sensing of Environment
Date : 2017
Volume : 200
Pages : 140–153
Catégorie(s)
#CIRAD #FORET ParacouAuteurs, date et publication :
Auteurs Laëtitia Bréchet , Valérie Le Dantec , Stéphane Ponton , Jean-Yves Goret , Emma Sayer , Damien Bonal , Vincent Freycon , Jacques Roy , Daniel Epron
Publication : Ecosystems
Date : 2017
Volume : 20
Issue : 6
Pages : 1190–1204
Catégorie(s)
#CIRAD #FORET ParacouRésumé
© 2017 The Author(s). Heterotrophic microorganisms are commonly thought to be stoichiometrically homeostatic but their stoichiometric plasticity has rarely been examined, particularly in terrestrial ecosystems. Using a fertilization experiment in a tropical rainforest, we evaluated how variable substrate stoichiometry may influence the stoichiometry of microbial communities in the leaf litter layer and in the underlying soil. C:N:P ratios of the microbial biomass were higher in the organic litter layer than in the underlying mineral soil. Regardless of higher ratios for litter microbial communities, C, N, and P fertilization effects on microbial stoichiometry were strong in both litter and soil, without any fundamental difference in plasticity between these two communities. Overall, N:P ratios were more constrained than C:nutrient ratios for both litter and soil microbial communities, suggesting that stoichiometric plasticity arises because of a decoupling between C and nutrients. Contrary to the simplifying premise of strict homeostasis in microbial decomposers, we conclude that both litter and soil communities can adapt their C:N:P stoichiometry in response to the stoichiometric imbalance of available resources.
Auteurs, date et publication :
Auteurs Nicolas Fanin , Nathalie Fromin , Sandra Barantal , Stephan Hättenschwiler
Publication : Scientific Reports
Date : 2017
Volume : 7
Issue : 1
Pages : 12498