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Gruhn, G., Dumez, S., Moreau, P. - A., Roy, M., Morreale, O., Schimann, H., et al. (2017). The genus Resinicium in French Guiana and the West Indies: a morphological and molecular survey, revealing Resinicium grandisporum sp. nov. Cryptogamie, Mycologie, 38(4), 1–15.
Abstract: A revision of Resinicium collections (Basidiomycota, Hymenochaetales) from French Guiana and French West Indies is provided, and a new species, Resinicium grandisporum sp. nov., supported by morphological as well as phylogenetic analyses based on ITS DNA sequences, is described and illustrated. An updated key of the genus Resinicium is also provided, which includes species previously described from outside of the studied area.
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Duplais, C., & Estevez, Y. (2017). Tandem Biocatalysis Unlocks the Challenging de Novo Production of Plant Natural Products. ChemBioChem, 18(22), 2192–2195.
Abstract: Intimate partnership: Knowledge of the biocatalytic cascades in different cellular compartments is limited, but deciphering these systems in nature can be used to inspire synthetic strategies. Two studies report new insights into the biosynthesis of alkaloids and sesterterpenoids in plants. This highlight presents these novel biotransformations to illustrate how tandem biocatalysis can impact the future of natural product production.
Keywords: alkaloids; biosynthesis; enzyme catalysis; protein engineering; terpenes
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Birer, C., Tysklind, N., Zinger, L., & Duplais, C. (2017). Comparative analysis of DNA extraction methods to study the body surface microbiota of insects: A case study with ant cuticular bacteria. Mol Ecol Resour, 17(6), e34–e45.
Abstract: High-throughput sequencing of the 16S rRNA gene has considerably helped revealing the essential role of bacteria living on insect cuticles in the ecophysiology and behaviour of their hosts. However, our understanding of host-cuticular microbiota feedbacks remains hampered by the difficulties of working with low bacterial DNA quantities as with individual insect cuticle samples, which are more prone to molecular biases and contaminations. Herein, we conducted a methodological benchmark on the cuticular bacterial loads retrieved from two Neotropical ant species of different body size and ecology: Atta cephalotes (~15 mm) and Pseudomyrmex penetrator (~5 mm). We evaluated the richness and composition of the cuticular microbiota, as well as the amount of biases and contamination produced by four DNA extraction protocols. We also addressed how bacterial community characteristics would be affected by the number of individuals or individual body size used for DNA extraction. Most extraction methods yielded similar results in terms of bacterial diversity and composition for A. cephalotes (~15 mm). In contrast, greater amounts of artefactual sequences and contaminations, as well as noticeable differences in bacterial community characteristics were observed between extraction methods for P. penetrator (~5 mm). We also found that large (~15 mm) and small (~5 mm) A. cephalotes individuals harbour different bacterial communities. Our benchmark suggests that cuticular microbiota of single individual insects can be reliably retrieved provided that blank controls, appropriate data cleaning, and individual body size and functional role within insect society are considered in the experiment.
Keywords: 16S rRNA; bacterial communities; cuticular microbiome; insect cuticle; metabarcoding
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Chang, S. - S., Quignard, F., & Clair, B. (2017). The effect of sectioning and ultrasonication on the mesoporosity of poplar tension wood. Wood Science and Technology, 51(3), 507–516.
Abstract: Increasing interest in understanding tension stress generation in tension wood with fibres having a gelatinous layer (G-layer) has focused attention on the specific role of this layer. To distinguish its contribution from those of other wall layers, the G-layer of wood sections was isolated by ultrasonication. The aim of this study was to assess the effect of sectioning and of the ultrasonic treatment on the mesoporosity of tension wood using nitrogen adsorption–desorption analysis. The results showed that the process of isolating the G-layer using ultrasonication strongly affects its mesoporosity. Most damage was found to occur during sectioning rather than as a result of the 15-min ultrasonic treatment.
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Stahl, C., Fontaine, S., Klumpp, K., Picon-Cochard, C., Grise, M. M., Dezecache, C., et al. (2017). Continuous soil carbon storage of old permanent pastures in Amazonia. Glob Change Biol, 23(8), 3382–3392.
Abstract: Amazonian forests continuously accumulate carbon (C) in biomass and in soil, representing a carbon sink of 0.42–0.65 GtC yr−1. In recent decades, more than 15% of Amazonian forests have been converted into pastures, resulting in net C emissions (~200 tC ha−1) due to biomass burning and litter mineralization in the first years after deforestation. However, little is known about the capacity of tropical pastures to restore a C sink. Our study shows in French Amazonia that the C storage observed in native forest can be partly restored in old (≥24 year) tropical pastures managed with a low stocking rate (±1 LSU ha−1) and without the use of fire since their establishment. A unique combination of a large chronosequence study and eddy covariance measurements showed that pastures stored between −1.27 ± 0.37 and −5.31 ± 2.08 tC ha−1 yr−1 while the nearby native forest stored −3.31 ± 0.44 tC ha−1 yr−1. This carbon is mainly sequestered in the humus of deep soil layers (20–100 cm), whereas no C storage was observed in the 0- to 20-cm layer. C storage in C4 tropical pasture is associated with the installation and development of C3 species, which increase either the input of N to the ecosystem or the C:N ratio of soil organic matter. Efforts to curb deforestation remain an obvious priority to preserve forest C stocks and biodiversity. However, our results show that if sustainable management is applied in tropical pastures coming from deforestation (avoiding fires and overgrazing, using a grazing rotation plan and a mixture of C3 and C4 species), they can ensure a continuous C storage, thereby adding to the current C sink of Amazonian forests.
Keywords: carbon storage; CN coupling; deep soil; mixed-grass pasture; native forest
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Mayer, V. E., Lauth, J., & Orivel, J. (2017). Convergent structure and function of mycelial galleries in two unrelated Neotropical plant-ants. Insectes Sociaux, 64(3), 365–371.
Abstract: The construction process and use of galleries by Azteca brevis (Myrmicinae: Dolichoderinae) inhabiting Tetrathylacium macrophyllum (Salicaceae) were compared with Allomerus decemarticulatus (Myrmicinae: Solenopsidini) galleries on Hirtella physophora (Chrysobalanaceae). Though the two ant species are phylogenetically distant, the gallery structure seems to be surprisingly similar and structurally convergent: both are pierced with numerous holes and both ant species use Chaetothyrialean fungi to strengthen the gallery walls. Al. decemarticulatus is known to use the galleries for prey capture and whether this is also the case for Az. brevis was tested in field experiments. We placed Atta workers as potential prey/threat on the galleries and recorded the behaviour of both ant species. We found considerable behavioural differences between them: Al. decemarticulatus was quicker and more efficient at capture than was Az. brevis. While most Atta workers were captured after the first 5 min by Al. decemarticulatus, significantly fewer were captured by Az. brevis even after 20 min. Moreover, the captured Atta were sometimes simply discarded and not taken to the nest by Az. brevis. As a consequence, the major function of the galleries built by Az. brevis may, therefore, be defense against intruders in contrast to Al. decemarticulatus which uses them mainly for prey capture. This may be due to a higher need for protein in Al. decemarticulatus compared to coccid-raising Az. brevis.
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Epelboin, L., Bourhy, P., Le Turnier, P., Schaub, R., Mosnier, E., Berlioz-Arthaud, A., et al. (2017). La leptospirose en Guyane française et sur le bouclier des Guyanes. État des connaissances en 2016. Bulletin de la Société de pathologie exotique, 110(3), 165–179.
Abstract: La leptospirose est une zoonose cosmopolite causée par les bactéries du genre Leptospira. Si sa répartition est vaste sur le globe, le climat chaud et humide de la zone intertropicale est particulièrement propice à son expansion. Dans la plupart des départements et territoires français d’outremer, la leptospirose est considérée comme un problème de santé publique. En Guyane, département français situé au nord-est de la forêt amazonienne, elle est considérée comme rare. L’objectif de cette revue est de faire l’état des lieux des connaissances sur la leptospirose humaine et animale en Guyane française et dans les pays environnants. Une recherche exhaustive a été conduite, à travers la littérature médicale indexée et informelle en français, anglais, espagnol et portugais. Ainsi, respectivement dix et quatre publications ont pu être identifiées sur la leptospirose humaine et animale en Guyane, publiées entre 1940 et 1995, sous formes de cas cliniques ou de séries de cas. Les publications concernant cette maladie dans les autres pays du plateau des Guyanes, Venezuela oriental, Guyana, Suriname, et État brésilien de l’Amapá, étaient également rares voire inexistantes. En revanche, les données récentes du centre national de la leptospirose français ont montré une augmentation récente et brutale du nombre de cas dans le département, probablement en partie due à la mise en place d’outils diagnostiques tels que la sérologie IgM Elisa. Il est en fait probable que la leptospirose soit une maladie négligée dans la région, du fait de l’absence d’outils diagnostiques rapidement disponibles, de la méconnaissance des cliniciens de cette pathologie et de l’existence de nombreux autres pathogènes à présentation clinique similaire (paludisme, arboviroses, fièvre Q, toxoplasmose amazonienne). La mise en place d’études de plus grande ampleur sur la leptospirose animale et humaine est nécessaire et urgente pour connaître le véritable poids de cette maladie dans notre région.
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Morel, H., Nicolini, E., Bossu, J., Blanc, L., & Beauchene, J. (2017). Qualité et usages du bois de cinq espèces forestières adaptées à la plantation à vocation de bois d’oeuvre et testées en Guyane française. Bois & Forêts des Tropiques, 334, 61–74.
Abstract: Des essais de plantations forestières ont été menés en Guyane française depuis le début des années 1960 sur plus de 138 espèces (70 espèces natives et 68 espèces exotiques). Une étude récente sur la productivité de ces espèces en plantation (projet ForesTreeCulture, 2013-2015) a mis en avant le fort potentieldeproductiondetroisespècesnatives ( Simarouba amara Aubl., Vochysia tomentosa (G. Mey.) DC., Bagassa guianensis ( Aubl.)) et d’une espèce d’Afrique de l’Ouest ( Tarrietia utilis Sprague) avec des volumes de bois produits supérieurs à 20 m3/ha/an. Cependant, les propriétés du bois de ces espèces commerciales ne sont connues qu’au travers d’arbres issus de forêt naturelle. Nous présentons les propriétés du bois de ces espèces en conditions de plantation – densité, retrait, élasticité, angle du fil, durabilité – et discutons de leurs potentiels et de leurs usages respectifs futurs. Une autre espèce, Cordia alliodora ((Ruiz et Pavon) Oken), a également été retenue bien qu’elle n’ait pas encore été plantée en Guyane française. Cette espèce, native de Guyane, est bien connue en Amérique latine pour son bois et son fort potentiel de croissance en milieu anthropisé.
Keywords: propriétés technologiques; qualité du bois; plantation; Guyane française
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Gourlet-Fleury, S., Gazull, L., Bigombe Logo, P., Billand, A., Bolaluembe, P. - C., Boyemba, F., et al. (2017). Are logging concessions a threat to the peatlands in DRC? Bois et Forets des Tropiques, (334), 3–6.
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Gomes, V. H. F., IJff, S. D., Raes, N., Amaral, I. L., Salomão, R. P., de Souza Coelho, L., et al. (2018). Species Distribution Modelling: Contrasting presence-only models with plot abundance data. Sci. Rep., 8, 1003.
Abstract: Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider this limitation, especially for large biodiversity assessments projects, when they are automatically generated without subsequent checking. Our pipeline provides a conservative estimate of a species’ area of occupancy, within an area slightly larger than its extent of occurrence, compatible to e.g. IUCN red list assessments.
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