Cantera, I., Cilleros, K., Valentini, A., Cerdan, A., Dejean, T., Iribar, A., et al. (2019). Optimizing environmental DNA sampling effort for fish inventories in tropical streams and rivers. Sci. Rep., 9, 3085.
Abstract: Environmental DNA (eDNA) metabarcoding is a promising tool to estimate aquatic biodiversity. It is based on the capture of DNA from a water sample. The sampled water volume, a crucial aspect for efficient species detection, has been empirically variable (ranging from few centiliters to tens of liters). This results in a high variability of sampling effort across studies, making comparisons difficult and raising uncertainties about the completeness of eDNA inventories. Our aim was to determine the sampling effort (filtered water volume) needed to get optimal inventories of fish assemblages in species-rich tropical streams and rivers using eDNA. Ten DNA replicates were collected in six Guianese sites (3 streams and 3 rivers), resulting in sampling efforts ranging from 17 to 340 liters of water. We show that sampling 34 liters of water detected more than 64% of the expected fish fauna and permitted to distinguish the fauna between sites and between ecosystem types (stream versus rivers). Above 68 liters, the number of detected species per site increased slightly, with a detection rate higher than 71%. Increasing sampling effort up to 340 liters provided little additional information, testifying that filtering 34 to 68 liters is sufficient to inventory most of the fauna in highly diverse tropical aquatic ecosystems. © 2019, The Author(s).
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Céréghino, R., Corbara, B., Hénaut, Y., Bonhomme, C., Compin, A., & Dejean, A. (2019). Ant and spider species as surrogates for functional community composition of epiphyte-associated invertebrates in a tropical moist forest. Ecological Indicators, 96, 694–700.
Abstract: Epiphytes represent up to 50% of all plant species in rainforests, where they host a substantial amount of invertebrate biomass. Efficient surrogates for epiphyte invertebrate communities could reduce the cost of biomonitoring surveys while preventing destructive sampling of the plants. Here, we focus on the invertebrate communities associated to tank bromeliads. We ask whether the presence of particular ant and/or spider taxa (easily surveyed taxa) that use these plants as nesting and/or foraging habitats predicts functional trait combinations of aquatic invertebrate communities hosted by the plants. Functional community composition of invertebrates was predicted both by bromeliad habitat features and the presence of certain ant and spider species. The ant Azteca serica preferred wider bromeliad rosettes that trap large amount of detritus, indicating interstitial-like food webs dominated by deposit feeders that burrow in fine particulate organic matter. Leucauge sp. spiders preferred narrower bromeliad rosettes bearing smaller detrital loads, thereby indicating a dominance of pelagic filter-feeding and predatory invertebrates in the water-filled leaf axils. Both Neoponera villosa ants and Eriophora sp. spiders preferred rosettes at intermediate size bearing moderate amounts of detritus, indicating a benthic food web dominated by leaf shredders and gathering collectors. Owing to the animal diversity and biomass supported by rainforest epiphytes, our approach would deserve to be further tested on a range of epiphytes involved in tight interactions with invertebrates. In this context, surrogate species could serve both as indicators of functional diversity, and as early-warning indicators of network disassembly.
Keywords: Functional traits; Indicator species; Phytotelmata; Rainforests; Surrogacy; Tank bromeliads
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Schepaschenko, D., Chave, J., Phillips, O. L., Lewis, S. L., Davies, S. J., Réjou-Méchain, M., et al. (2019). The Forest Observation System, building a global reference dataset for remote sensing of forest biomass. Scientific data, 6(198).
Abstract: Forest biomass is an essential indicator for monitoring the Earth's ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world's forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.
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Richard-Hansen, C., Davy, D., Longin, G., Gaillard, L., Renoux, F., Grenand, P., et al. (2019). Hunting in French Guiana Across Time, Space and Livelihoods. Frontiers in Ecology and Evolution, 7, 289.
Abstract: Hunting sustainability in Amazonian ecosystems is a key challenge for modern stakeholders. Predictive models have evolved from first mostly biological data-based to more recent modelling including human behavior. We analyze here the hunting data collected in French Guiana through a panel of indices aiming at drawing the puzzle of parameters influencing hunting activity and impact in various socio ecological conditions across the country. Data were collected from five different study sites differing in cultural origins and remoteness from market economy, and over a ten years period. Most indices show an impact on wildlife populations, and using a full set of indicators allowed us to better understand some underlying mechanisms that lead to a community’s hunting profile. The results showed that there are noticeable differences between the study sites in the practices and the ways hunters face the changes in environment and resources availability
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Ciminera, M., Auger-Rozenberg, M. - A., Caron, H., Herrera, M., Scotti-Saintagne, C., Scotti, I., et al. (2019). Genetic Variation and Differentiation of Hylesia metabus (Lepidoptera: Saturniidae): Moths of Public Health Importance in French Guiana and in Venezuela. J. Med. Entomol., 56(1), 137–148.
Abstract: Hylesia moths impact human health in South America, inducing epidemic outbreaks of lepidopterism, a puriginous dermatitis caused by the urticating properties of females' abdominal setae. The classification of the Hylesia genus is complex, owing to its high diversity in Amazonia, high intraspecific morphological variance, and lack of interspecific diagnostic traits which may hide cryptic species. Outbreaks of Hylesia metabus have been considered responsible for the intense outbreaks of lepidopterism in Venezuela and French Guiana since the C20, however, little is known about genetic variability throughout the species range, which is instrumental for establishing control strategies on H. metabus. Seven microsatellites and mitochondrial gene markers were analyzed from Hylesia moths collected from two major lepidopterism outbreak South American regions. The mitochondrial gene sequences contained significant genetic variation, revealing a single, widespread, polymorphic species with distinct clusters, possibly corresponding to populations evolving in isolation. The microsatellite markers validated the mitochondrial results, and suggest the presence of three populations: one in Venezuela, and two in French Guiana. All moths sampled during outbreak events in French Guiana were assigned to a single coastal population. The causes and implications of this finding require further research.
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Jaouen, G., Sagne, A., Buyck, B., Decock, C., Louisanna, E., Manzi, S., et al. (2019). Fungi of French Guiana gathered in a taxonomic, environmental and molecular dataset. Scientific data, 6(206).
Abstract: In Amazonia, the knowledge about Fungi remains patchy and biased towards accessible sites. This is particularly the case in French Guiana where the existing collections have been confined to few coastal localities. Here, we aimed at filling the gaps of knowledge in undersampled areas of this region, particularly focusing on the Basidiomycota. From 2011, we comprehensively collected fruiting-bodies with a stratified and reproducible sampling scheme in 126 plots. Sites of sampling reflected the main forest habitats of French Guiana in terms of soil fertility and topography. The dataset of 5219 specimens gathers 245 genera belonging to 75 families, 642 specimens are barcoded. The dataset is not a checklist as only 27% of the specimens are identified at the species level but 96% are identified at the genus level. We found an extraordinary diversity distributed across forest habitats. The dataset is an unprecedented and original collection of Basidiomycota for the region, making specimens available for taxonomists and ecologists. The database is publicly available in the GBIF repository ( https://doi.org/10.15468/ymvlrp ).
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Leroy, C., Maes, A. Q., Louisanna, E., & Séjalon-Delmas, N. (2019). How significant are endophytic fungi in bromeliad seeds and seedlings? Effects on germination, survival and performance of two epiphytic plant species. Fungal Ecol., 39, 296–306.
Abstract: In bromeliads, nothing is known about the associations fungi form with seeds and seedling roots. We investigated whether fungal associations occur in the seeds and seedling roots of two epiphytic Aechmea species, and we explored whether substrate and fungal associations contribute to seed germination, and seedling survival and performance after the first month of growth. We found a total of 21 genera and 77 species of endophytic fungi in the seeds and seedlings for both Aechmea species by Illumina MiSeq sequencing. The fungal associations in seeds were found in the majority of corresponding seedlings, suggesting that fungi are transmitted vertically. Substrate quality modulated the germination and growth of seedlings, and beneficial endophytic fungi were not particularly crucial for germination but contributed positively to survival and growth. Overall, this study provides the first evidence of an endophytic fungal community in both the seeds and seedlings of two epiphytic bromeliads species that subsequently benefit plant growth. © 2019 Elsevier Ltd and British Mycological Society
Keywords: Aechmea; Bromeliads; Endophytic fungi; Fusarium spp.; Germination; Survival; Trichoderma spp.; Vertical transmission
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Barassé, V., Touchard, A., Téné, N., Tindo, M., Kenne, M., Klopp, C., et al. (2019). The peptide venom composition of the fierce stinging ant tetraponera aethiops (formicidae: Pseudomyrmecinae). Toxins, 11(12), 732.
Abstract: In the mutualisms involving certain pseudomyrmicine ants and different myrmecophytes (i.e., plants sheltering colonies of specialized “plant-ant” species in hollow structures), the ant venom contributes to the host plant biotic defenses by inducing the rapid paralysis of defoliating insects and causing intense pain to browsing mammals. Using integrated transcriptomic and proteomic approaches, we identified the venom peptidome of the plant-ant Tetraponera aethiops (Pseudomyrmecinae). The transcriptomic analysis of its venom glands revealed that 40% of the expressed contigs encoded only seven peptide precursors related to the ant venom peptides from the A-superfamily. Among the 12 peptide masses detected by liquid chromatography-mass spectrometry (LC-MS), nine mature peptide sequences were characterized and confirmed through proteomic analysis. These venom peptides, called pseudomyrmecitoxins (PSDTX), share amino acid sequence identities with myrmeciitoxins known for their dual offensive and defensive functions on both insects and mammals. Furthermore, we demonstrated through reduction/alkylation of the crude venom that four PSDTXs were homo- and heterodimeric. Thus, we provide the first insights into the defensive venom composition of the ant genus Tetraponera indicative of a streamlined peptidome.
Keywords: Defensive venom; Dimeric peptides; Peptidome; Tetraponera aethiops
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Aubry-Kientz, M., Rossi, V., Cornu, G., Wagner, F., & Herault, B. (2019). Temperature rising would slow down tropical forest dynamic in the Guiana Shield. Sci. Rep., 9, 10235.
Abstract: Increasing evidence shows that the functioning of the tropical forest biome is intimately related to the climate variability with some variables such as annual precipitation, temperature or seasonal water stress identified as key drivers of ecosystem dynamics. How tropical tree communities will respond to the future climate change is hard to predict primarily because several demographic processes act together to shape the forest ecosystem general behavior. To overcome this limitation, we used a joint individual-based model to simulate, over the next century, a tropical forest community experiencing the climate change expected in the Guiana Shield. The model is climate dependent: temperature, precipitation and water stress are used as predictors of the joint growth and mortality rates. We ran simulations for the next century using predictions of the IPCC 5AR, building three different climate scenarios (optimistic RCP2.6, intermediate, pessimistic RCP8.5) and a control (current climate). The basal area, above-ground fresh biomass, quadratic diameter, tree growth and mortality rates were then computed as summary statistics to characterize the resulting forest ecosystem. Whatever the scenario, all ecosystem process and structure variables exhibited decreasing values as compared to the control. A sensitivity analysis identified the temperature as the strongest climate driver of this behavior, highlighting a possible temperature-driven drop of 40% in average forest growth. This conclusion is alarming, as temperature rises have been consensually predicted by all climate scenarios of the IPCC 5AR. Our study highlights the potential slow-down danger that tropical forests will face in the Guiana Shield during the next century. © 2019, The Author(s).
Keywords: article; biomass; climate change; controlled study; diagnostic test accuracy study; driver; human; joint; mortality rate; precipitation; prediction; sensitivity analysis; simulation; statistics; tree growth; tropical rain forest; water stress
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Lehnebach, R., Bossu, J., Va, S., Morel, H., Amusant, N., Nicolini, E., et al. (2019). Wood density variations of legume trees in French Guiana along the shade tolerance continuum: Heartwood effects on radial patterns and gradients. Forests, 10(2).
Abstract: Increasing or decreasing wood density (WD) from pith to bark is commonly observed in tropical tree species. The different types of WD radial variations, long been considered to depict the diversity of growth and mechanical strategies among forest guilds (heliophilic vs. shade-tolerant), were never analyzed in the light of heartwood (HW) formation. Yet, the additional mass of chemical extractives associated to HW formation increases WD and might affect both WD radial gradient (i.e., the slope of the relation between WD and radial distance) and pattern (i.e., linear or nonlinear variation). We studied 16 legumes species from French Guiana representing a wide diversity of growth strategies and positions on the shade-tolerance continuum. Using WD measurements and available HW extractives content values, we computed WD corrected by the extractive content and analyzed the effect of HW on WD radial gradients and patterns. We also related WD variations to demographic variables, such as sapling growth and mortality rates. Regardless of the position along the shade-tolerance continuum, correcting WD gradients reveals only increasing gradients. We determined three types of corrected WD patterns: (1) the upward curvilinear pattern is a specific feature of heliophilic species, whereas (2) the linear and (3) the downward curvilinear patterns are observed in both mid- and late-successional species. In addition, we found that saplings growth and mortality rates are better correlated with the corrected WD at stem center than with the uncorrected value: taking into account the effect of HW extractives on WD radial variations provides unbiased interpretation of biomass accumulation and tree mechanical strategies. Rather than a specific feature of heliophilic species, the increasing WD gradient is a shared strategy regardless of the shade tolerance habit. Finally, our study stresses to consider the occurrence of HW when using WD.
Keywords: French Guiana; Growth-mortality rate; Heartwood; Heartwood extractives; Legumes; Sapwood; Shade tolerance; Tropical tree species; Wood density variations
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