Éditeur(s) : HAL CCSD
International statistical ecology conference 2014
Montpellier, France

hal-01503286
https://hal-agroparistech.archives-ouvertes.fr/hal-01503286

Éditeur(s) : HAL CCSD American Mosquito Control Association
Résumé : Research on natural insecticides has intensified with the spread of resistance to chemicals among insects, particularly disease vectors. To evaluate compounds, the World Health Organization (WHO) has published standardized procedures. However, those may be excessively compound-consuming when it comes to assessing the activity of natural extracts and pure compounds isolated in limited amount. As part of our work on the discovery of new mosquito larvicides from Amazonian plants, we developed a compound-saving assay in 5-ml glass tubes instead of WHO larval 100-m1 cups. Comparing activity of synthetic and natural chemicals validated the glass tube assay. Raw data, lethal doses that kill 50% (LD50) and 90% (LD90) at 24 and 48 h, were highly correlated (0.68 < R-2 < 0.96, P < 0.001, Pearson test) between cups and tubes. It was also established that 10 tubes (N = 50 larvae) provided the same level of sensitivity as 20 tubes (N= 100). This method proved suitable for rapid screening of natural extracts and molecules, identifying active compounds using 10 times less material than in the WHO protocol.
ISSN: 8756-971X

hal-01602207
https://hal.archives-ouvertes.fr/hal-01602207
DOI : 10.2987/16-6613.1
PRODINRA : 394297
PUBMED : 28206865

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Ethnopharmacological relevancePsidium acutangulum Mart. ex DC is a small tree used by the Wayana Amerindians from the Upper-Maroni in French Guiana for the treatment of malaria.Aim of the studyIn a previous study, we highlighted the in vitro antiplasmodial, antioxidant and anti-inflammatory potential of the traditional decoction of P. acutangulum aerial parts. Our goal was then to investigate on the origin of the biological activity of the traditional remedy, and eventually characterize active constituents.Materials and methodsLiquid-liquid extractions were performed on the decoction, and the antiplasmodial activity evaluated against chloroquine-resistant FcB1 ([3H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains, and on a chloroquine sensitive NF54 ([3H]-hypoxanthine bioassay) P. falciparum strain. The ethyl acetate fraction (D) was active and underwent bioguided fractionation. All the isolated compounds were tested on P. falciparum FcB1 strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) of the ethyl acetate fraction and of an anti-Plasmodium active compound, was concurrently assessed on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the fractions and pure compounds was measured on VERO cells, L6 mammalian cells, PBMCs, and RAW cells.ResultsFractionation of the ethyl acetate soluble fraction (IC50 ranging from 3.4 to <1 µg/mL depending on the parasite strain) led to the isolation of six pure compounds: catechin and five glycosylated quercetin derivatives. These compounds have never been isolated from this plant species. Two of these compounds (wayanin and guaijaverin) were found to be moderately active against P. falciparum FcB1 in vitro (IC50 5.5 and 6.9 µM respectively). We proposed the name wayanin during public meetings organized in June 2015 in the Upper-Maroni villages, in homage to the medicinal knowledge of the Wayana population. At 50 µg/mL, the ethyl acetate fraction (D) significantly inhibited IL-1β secretion (−46%) and NO production (−21%), as previously observed for the decoction. The effects of D and guiajaverin (4) on the secretion of other cytokines or NO production were not significant.ConclusionsThe confirmed antiplasmodial activity of the ethyl acetate soluble fraction of the decoction and of the isolated compounds support the previous results obtained on the P. acutangulum decoction. The antiplasmodial activity might be due to a mixture of moderately active non-toxic flavonoids. The anti-inflammatory activities were less marked for ethyl acetate fraction (D) than for the decoction.
ISSN: 0378-8741

hal-01313006
http://hal.upmc.fr/hal-01313006
http://hal.upmc.fr/hal-01313006/document
http://hal.upmc.fr/hal-01313006/file/Houel_Wayanin_and.pdf
DOI : 10.1016/j.jep.2016.04.053

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
ISSN: 1874-3900

hal-01152699
https://hal.archives-ouvertes.fr/hal-01152699
DOI : 10.1016/j.phytol.2015.03.012

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : International audience
Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages , we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.
ISSN: 0962-8452

hal-01323255
https://hal.archives-ouvertes.fr/hal-01323255
DOI : 10.1098/rspb.2015.0418

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
Most eukaryotic organisms are arthropods. Yet, their diversity in rich terrestrial ecosystems is still unknown. Here we produce tangible estimates of the total species richness of arthropods in a tropical rainforest. Using a comprehensive range of structured protocols, we sampled the phylogenetic breadth of arthropod taxa from the soil to the forest canopy in the San Lorenzo forest, Panama. We collected 6144 arthropod species from 0.48 hectare and extrapolated total species richness to larger areas on the basis of competing models. The whole 6000-hectare forest reserve most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of the arthropod biodiversity held in the wider landscape. Models based on plant diversity fitted the accumulated species richness of both herbivore and nonherbivore taxa exceptionally well. This lends credence to global estimates of arthropod biodiversity developed from plant models.
ISSN: 0036-8075

hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285/document
https://hal.archives-ouvertes.fr/hal-00817285/file/1226727Revisedtext.pdf
DOI : 10.1126/science.1226727

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : Growth defense tradeoff theory predicts that plants in low-resource habitats invest more energy in defense mechanisms against natural enemies than growth, whereas plants in high-resource habitats can afford higher leaf loss rates. A less-studied defense against herbivores involves the synchrony of leaf production, which can be an effective defense strategy if leaf biomass production exceeds the capacity of consumption by insects. The aim of this study was to determine whether leaf synchrony varied across habitats with different available resources and whether insects were able to track young leaf production among tree habitat specialists in a tropical forest of French Guiana. We predicted that high-resource habitats would exhibit more synchrony in leaf production due to the low cost and investment to replace leaf tissue. We also expected closer patterns of leaf synchrony and herbivory within related species, assuming that they shared herbivores. We simultaneously monitored leaf production and herbivory rates of five pairs of tree species, each composed of a specialist of terra firme or white-sand forests within the same lineage. Our prediction was not supported by the strong interaction of habitat and lineage for leaf synchrony within individuals of the same species; although habitat specialists differed in leaf synchrony within four of five lineages, the direction of the effect was variable. All species showed short time lags for the correlation between leaf production and herbivory, suggesting that insects are tightly tracking leaf production, especially for the most synchronous species. Leaf synchrony may provide an important escape defense against herbivores, and its expression appears to be constrained by both evolutionary history and environmental factors.
ISSN: 1385-0237

hal-01204221
https://hal.archives-ouvertes.fr/hal-01204221
DOI : 10.1007/s11258-013-0290-y
PRODINRA : 288500

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
In French Guiana, Quassia amara L. (Simaroubaceae) leaf tea is a well-known widely used traditional antimalarial remedy. Impact of the vegetal sampling condition on in vivo and in vitro antimalarial activity was assessed. Traditional infusions were prepared with juvenile or mature leaves, both either fresh or dried. Results showed that growing stage and freshness of vegetal material exert a striking effect on antimalarial activity, both in vitro and in vivo. By far, leaf tea made from fresh juvenile (FJ) Quassia amara leaves was the most active. In vitro, active component (simalikalactone D) concentration correlates biological activities, although unexplained subtle variations were observed. In vivo, tea made with dried juvenile (DJ) leaves displays a peculiar behavior, meaning that some components may help simalikalactone D delivery or may be active in vivo only, therefore enhancing the expected curative effect of the traditional preparation.
ISSN: 0378-8741

hal-00384338
https://hal.archives-ouvertes.fr/hal-00384338
DOI : 10.1016/j.jep.2006.10.028

Éditeur(s) : HAL CCSD Instituto Oswaldo Cruz, Ministério da Saúde
Résumé : International audience
This study examined whether the antidermatophytic activity of essential oils (EOs) can be used as an indicator for the discovery of active natural products against Leishmania amazonensis. The aerial parts of seven plants were hydro-distilled. Using broth microdilution techniques, the obtained EOs were tested against three strains of dermatophytes (Trichophyton mentagrophytes, Microsporum gypseum and Microsporum canis). To compare the EOs antifungal and antiparasitic effects, the EOs activities against axenic amastigotes of L. amazonensis were concurrently evaluated. For the most promising EOs, their antileishmanial activities against parasites infecting peritoneal macrophages of BALB/c mice were measured. The most interesting antifungal candidates were the EOs from Cymbopogon citratus, Otacanthus azureus and Protium heptaphyllum, whereas O. azureus, Piper hispidum and P. heptaphyllum EOs exhibited the lowest 50% inhibitory concentration (IC 50) values against axenic amastigotes, thus revealing a certain correspondence between both activities. The P. hispidum EO was identified as the most promising product in the results from the infected macrophages model (IC 50 : 4.7 µg/mL, safety index: 8). The most abundant compounds found in this EO were sesquiter-penes, notably curzerene and furanodiene. Eventually, the evaluation of the antidermatophytic activity of EOs appears to be an efficient method for identifying new potential drugs for the treatment of L. amazonensis.
ISSN: 0074-0276

Droits : http://creativecommons.org/licenses/by/
hal-01230471
http://hal.upmc.fr/hal-01230471
http://hal.upmc.fr/hal-01230471/document
http://hal.upmc.fr/hal-01230471/file/0074-0276-mioc-0140332.pdf
DOI : 10.1590/0074-02760140332

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
We conducted a survey along three belt transects located at increasing distances from the coast to determine whether a non-random arboreal ant assemblage, such as an ant mosaic, exists in the rainforest on the Masoala Peninsula, Madagascar. In most tropical rainforests, very populous colonies of territorially dominant arboreal ant species defend absolute territories distributed in a mosaic pattern. Among the 29 ant species recorded, only nine had colonies large enough to be considered potentially territorially dominant; the remaining species had smaller colonies and were considered non-dominant. Nevertheless, the null-model analyses used to examine the spatial structure of their assemblages did not reveal the existence of an ant mosaic. Inland, up to 44% of the trees were devoid of dominant arboreal ants, something not reported in other studies. While two Crematogaster species were not associated with one another, Brachymyrmex cordemoyi was positively associated with Technomyrmex albipes, which is considered an invasive species-a non-indigenous species that has an adverse ecological effect on the habitats it invades. The latter two species and Crematogaster ranavalonae were mutually exclusive. On the other hand, all of the trees in the coastal transect and at least 4 km of coast were occupied by T. albipes, and were interconnected by columns of workers. Technomyrmex albipes workers collected from different trees did not attack each other during confrontation tests, indicating that this species has formed a supercolony along the coast. Yet interspecific aggressiveness did occur between T. albipes and Crematogaster ranavalonae, a native species which is likely territorially dominant based on our intraspecific confrontation tests. These results suggest that the Masoala rainforest is threatened by a potential invasion by T. albipes, and that the penetration of this species further inland might be facilitated by the low density of native, territorially dominant arboreal ants normally able to limit its progression.
ISSN: 1932-6203

hal-00817444
https://hal.archives-ouvertes.fr/hal-00817444
https://hal.archives-ouvertes.fr/hal-00817444/document
https://hal.archives-ouvertes.fr/hal-00817444/file/Dejean2010_Spatial.pdf
DOI : 10.1371/journal.pone.0009319

Éditeur(s) : HAL CCSD American Society for Microbiology
Résumé :  
We report the isolation and identification of a new quassinoid named simalikalactone E (SkE), extracted from a widely used Amazonian antimalarial remedy made out of Quassia amara L. (Simaroubaceae) leaves. This new molecule inhibited the growth of Plasmodium falciparum cultured in vitro by 50%, in the concentration range from 24 to 68 nM, independently of the strain sensitivity to chloroquine. We also showed that this compound was able to decrease gametocytemia with a 50% inhibitory concentration sevenfold lower than that of primaquine. SkE was found to be less toxic than simalikalactone D (SkD), another antimalarial quassinoid from Q. amara, and its cytotoxicity on mammalian cells was dependent on the cell line, displaying a good selectivity index when tested on nontumorogenic cells. In vivo, SkE inhibited murine malaria growth of Plasmodium vinckei petteri by 50% at 1 and 0.5 mg/kg of body weight/day, by the oral or intraperitoneal routes, respectively. The contribution of quassinoids as a source of antimalarial molecules needs therefore to be reconsidered.
ISSN: 0066-4804

hal-01032126
https://hal.archives-ouvertes.fr/hal-01032126
DOI : 10.1128/AAC.00951-09

Éditeur(s) : HAL CCSD Le Cherche midi CNRS
Résumé : 192 pages
National audience
https://hal.archives-ouvertes.fr/hal-01118878

ISBN : 978-2-7491-4075-9
hal-01118878
https://hal.archives-ouvertes.fr/hal-01118878

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The chemical investigations of Dicorynia guianensis heartwood led to the isolation of four new indole alkaloids for the first time in this plant. Compound (1) identified as spiroindolone 20,30,40,90-tetrahydrospiro [indoline-3,10pyrido[3,4-b]-indol]-2-one, and compound (3) described as nitrone 1-methyl-4,9-dihydro-3H-pyrido [3,4-b] indole 2-oxide and were isolated for the first time as natural products. ABTS antioxidant activity guided their isolation.
ISSN: 1874-3900

hal-01138910
https://hal.archives-ouvertes.fr/hal-01138910
DOI : 10.1016/j.phytol.2015.03

Éditeur(s) : HAL CCSD European Geosciences Union
Résumé : International audience
The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1).
ISSN: 1726-4170

hal-01557759
https://hal.univ-lorraine.fr/hal-01557759
https://hal.univ-lorraine.fr/hal-01557759/document
https://hal.univ-lorraine.fr/hal-01557759/file/bg-13-2537-2016.pdf
DOI : 10.5194/bg-13-2537-2016

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997-2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals.
ISSN: 1932-6203

hal-00825825
https://hal.archives-ouvertes.fr/hal-00825825
https://hal.archives-ouvertes.fr/hal-00825825/document
https://hal.archives-ouvertes.fr/hal-00825825/file/Dejean2011_Climate.pdf
DOI : 10.1371/journal.pone.0027004

Éditeur(s) : HAL CCSD MDPI
Résumé : International audience
Canopy height is a key variable in tropical forest functioning and for regional carbon inventories. We investigate the spatial structure of the canopy height of a tropical forest, its relationship with environmental physical covariates, and the implication for tropical forest height variation mapping. Making use of high-resolution maps of LiDAR-derived Digital Canopy Model (DCM) and environmental covariates from a Digital Elevation Model (DEM) acquired over 30,000 ha of tropical forest in French Guiana, we first show that forest canopy height is spatially correlated up to 2500 m. Forest canopy height is significantly associated with environmental variables, but the degree of correlation varies strongly with pixel resolution. On the whole, bottomland forests generally have lower canopy heights than hillslope or hilltop forests. However, this global picture is very noisy at local scale likely because of the endogenous gap-phase forest dynamic processes. Forest canopy height has been predictively mapped across a pixel resolution going from 6 m to 384 m mimicking a low resolution case of 3 points·km −2. Results of canopy height mapping indicated that the error for spatial model with environment effects decrease from 8.7 m to 0.91 m, depending of the pixel resolution. Results suggest that, outside the calibration plots, the contribution of environment in shaping the global canopy height distribution is quite limited. This prevents accurate canopy height mapping based only on environmental information, and suggests that precise canopy height maps, for local management purposes, can only be obtained with direct LiDAR monitoring.
ISSN: 2072-4292

hal-01590726
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590726
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590726/document
https://hal-univ-guyane.archives-ouvertes.fr/hal-01590726/file/remotesensing-08-00747.pdf
DOI : 10.3390/rs8090747

Éditeur(s) : HAL CCSD American Chemical Society
Résumé : Three new monoterpene indole alkaloids (13) have been isolated from the bark of Geissospermum laeve-, together with the known alkaloids (-)-leuconolam (4), geissolosimine (5), and geissospermine (6). The structures of 1-3 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of geissolaevine (I). was deduced from the comparison of experimental and theoretically calculated ECD spectra. The isolation workflow was guided by a molecular networking-based dereplication strategy using an in-house database of monoterpene indole alkaloids. In addition, five known compounds previously undescribed in the Geissospermum genus were dereplicated from the G. laeve alkaloid extract network and were assigned with various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum and Leishmania donovani as well as the Ortotoxic activity against the MRC-5 cell line were determined for compounds 1-5.
ISSN: 0163-3864

hal-01605065
https://hal.archives-ouvertes.fr/hal-01605065
DOI : 10.1021/acs.jnatprod.6b01013
PRODINRA : 402605
PUBMED : 28282127

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : The area of forest plantations is increasing worldwide helping to meet timber demand and protect natural forests. However, with global change, monospecific plantations are increasingly vulnerable to abiotic and biotic disturbances. As an adaption measure we need to move to plantations that are more diverse in genotypes, species, and structure, with a design underpinned by science. TreeDivNet, a global network of tree diversity experiments, responds to this need by assessing the advantages and disadvantages of mixed species plantations. The network currently consists of 18 experiments, distributed over 36 sites and five ecoregions. With plantations 1-15 years old, TreeDivNet can already provide relevant data for forest policy and management. In this paper, we highlight some early results on the carbon sequestration and pest resistance potential of more diverse plantations. Finally, suggestions are made for new, innovative experiments in understudied regions to complement the existing network.
ISSN: 0044-7447

hal-01204232
https://hal.archives-ouvertes.fr/hal-01204232
DOI : 10.1007/s13280-015-0685-1
PRODINRA : 324368
PUBMED : 26264716

Éditeur(s) : HAL CCSD Springer Verlag
Résumé :  
The high spatial variability of soil respiration in tropical rainforests is well evaluated, but influences of biotic factors are not clearly understood. This study underlines the influence of tree species characteristics on soil respiration across a 16-monospecific plot design in a tropical plantation of French Guiana. A large variability of soil CO2 fluxes was observed among plots (i.e. 2.8 to 6.8 μmol m−2 s −1 ) with the ranking being constant across seasons. There were no significant relationships between soil respiration and soil moisture or soil temperature, neither spatially, nor seasonally. The variability of soil respiration was mainly explained by quantitative factors such as leaf litterfall and basal area. Surprisingly, no significant relationship was observed between soil respiration and root biomass. However, the influence of substrate quality was revealed by a strong relationship between soil respiration and litterfall P (and litterfall N, to a lesser extent).
ISSN: 0032-079X

hal-01032069
https://hal.archives-ouvertes.fr/hal-01032069
DOI : 10.1007/s11104-008-9866-z

Éditeur(s) : HAL CCSD
Résumé : International audience
The corrosion rates in the presence of some indole derivates, namely, 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane), as inhibitors of C38 steel corrosion inhibitor in 1 M HCl solution, were measured by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, in the range of temperatures from 25 to 55∘C. Results obtained revealed that the organic compounds investigated have inhibiting properties for all temperatures. The inhibition was assumed to occur via adsorption of the indole molecules on the metal surface. Adsorption of indole derivates was found to follow the Langmuir isotherm. The apparent activation energies, enthalpies, and entropies of the dissolution process and the free energies and enthalpies for the adsorption process were determined by potentiodynamic polarization and electrochemical impedance. The fundamental thermodynamic functions were used to collect important information about indole inhibitory behaviour.
international Journal of Corrosion

hal-01683120
https://hal.univ-antilles.fr/hal-01683120
DOI : 10.1155/2013/139798