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Delnatte, C., & Meyer, J. - Y. (2012). Plant introduction, naturalization, and invasion in French Guiana (South America). Biol. Invasions, 14(5), 915–927.
Abstract: Continental tropical ecosystems are generally viewed as less vulnerable to biological invasions than island ones. Their apparent resistance to invasive alien species is often attributed to their higher native biota diversity and complexity. However, with the increase of human activities and disturbances and the accelerate rate of introductions of plant species, these apparently resilient continental ecosystems are now experiencing alien plant naturalization and invasion events. In order to illustrate this emergent phenomenon, we compiled a list of all known introduced and naturalized plant species in French Guiana (Guiana Shield, South America). A total of 490 alien plants were recorded, about 34% of which are currently naturalized, mainly species belonging to the Acanthaceae and Fabaceae (Faboideae) in the Eudicotyledons, and Poaceae (grasses) and Arecaceae (palms) in the Monocotyledons. The coastal dry and wet savannas appears to be vulnerable to plant invasion (with 165 naturalized species, about 34% of the alien flora), especially by Acacia mangium (Mimosaceae) and Melaleuca quinquenervia (Myrtaceae) which are forming localized but dense monotypic stands. Both tree species, intentionnally introduced for reforestation, rehabilitation, and as garden ornamentals and have the potential to spread with increasing human disturbances The number and abundance of naturalized alien plants in the relatively undisturbed tropical lowland rainforests and savannas remains still very low. Therefore, surveillance, early detection, and eradication of potential plant invaders are crucial; moreover collaboration with neighbouring countries of the Guiana Shield is essential to prevent the introduction of potentially invasive species which are still not present in French Guiana. © 2011 Springer Science+Business Media B.V.
Keywords: Acacia mangium; French Guiana; Invasive plant; Melaleuca quinquenervia; Naturalization; Savanna
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Kunstler, G., Falster, D., Coomes, D. A., Hui, F., Kooyman, R. M., Laughlin, D. C., et al. (2016). Plant functional traits have globally consistent effects on competition. Nature, 529(7585), 204–207.
Abstract: Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions, but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear. Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits – wood density, specific leaf area and maximum height – consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies. Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our trait-based approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition. © 2016 Macmillan Publishers Limited. All rights reserved.
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Cachet, N., Ho-A-Kwie, F., Rivaud, M., Houel, E., Deharo, E., Bourdy, G., et al. (2012). Picrasin K, a new quassinoid from Quassia amara L. (Simaroubaceae). Phytochem. Lett., 5(1), 162–164.
Abstract: A new quassinoid Picrasin K 1 was isolated from a decoction made of Quassia amara leaves, traditionally used in French Guyana to treat malaria. The structure and relative stereochemistry of 1 was determined through extensive NMR analysis. Picrasin K showed a low activity against Plasmodium falciparum in vitro (IC 50 = 8 μM), and a similar low activity on human cancerous cells line (IC 50 = 7 μM on MCF-7 cells line). © 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
Keywords: Malaria; P. falciparum; Quassia amara; Quassinoids; Simaroubaceae
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Michalet, S., Rohr, J., Warshan, D., Bardon, C., Roggy, J. - C., Domenach, A. - M., et al. (2013). Phytochemical analysis of mature tree root exudates in situ and their role in shaping soil microbial communities in relation to tree N-acquisition strategy. Plant Physiol. Biochem., 72, 169–177.
Abstract: Eperua falcata (Aublet), a late-successional species in tropical rainforest and one of the most abundant tree in French Guiana, has developed an original strategy concerning N-acquisition by largely preferring nitrate, rather than ammonium (H. Schimann, S. Ponton, S. Hättenschwiler, B. Ferry, R. Lensi, A.M. Domenach, J.C. Roggy, Differing nitrogen use strategies of two tropical rainforest tree species in French Guiana: evidence from 15N natural abundance and microbial activities, Soil Biol. Biochem. 40 (2008) 487-494). Given the preference of this species for nitrate, we hypothesized that root exudates would promote nitrate availability by (a) enhancing nitrate production by stimulating ammonium oxidation or (b) minimizing nitrate losses by inhibiting denitrification.Root exudates were collected in situ in monospecific planted plots. The phytochemical analysis of these exudates and of several of their corresponding root extracts was achieved using UHPLC/DAD/ESI-QTOF and allowed the identification of diverse secondary metabolites belonging to the flavonoid family.Our results show that (i) the distinct exudation patterns observed are related to distinct root morphologies, and this was associated with a shift in the root flavonoid content, (ii) a root extract representative of the diverse compounds detected in roots showed a significant and selective metabolic inhibition of isolated denitrifiers invitro, and (iii) in soil plots the abundance of nirK-type denitrifiers was negatively affected in rhizosphere soil compared to bulk. Altogether this led us to formulate hypothesis concerning the ecological role of the identified compounds in relation to N-acquisition strategy of this species. © 2013 Elsevier Masson SAS.
Keywords: Chemical ecology; Denitrification; Eperua falcata; Metabolic profiling; Mycorrhizae; Plant-microbes interactions; Root exudates
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Bremaud, I., Minato, K., Langbour, P., & Thibaut, B. (2010). Physico-chemical indicators of inter-specific variability in vibration damping of wood. Ann. For. Sci., 67(7), 707.
Abstract: The vibration damping coefficient (tan delta) of wood is an important property for acoustical uses, including musical instruments. Current difficulties in the availability of some of the preferred species call for diversification, but this comes up against the lack of systematic damping coefficient data. Keeping in mind the possible factors affecting tans, could we predict its variations between species, by using indicators that are either easily measured and/or readily available for many species? Vibrational properties, equilibrium moisture content and colorimetric parameters were assessed on 94 wood types belonging to 76 species. Experimental results were then related to data on chemical contents and physical properties from the CIRAD database. The “standard” relationship between tan delta and specific modulus of elasticity (E'/rho) explained only half of the variations. Deviations from this trend were correlated to extractives content, yet effects were not directly quantitative. Damping deviations were also correlated to colour and moisture-related properties, especially so with fibre saturation point. By taking into account a combination of moisture-related properties, colour – or extractives content, and the “standard” relationship between tans and E'/rho, we could propose simple predictive models which explain up to 89% of observed variations in tan delta between 48 species.
Keywords: damping coefficient; diversity of woods; extractives; physical properties; vibrational properties
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Scotti-Saintagne, C., Dick, C. W., Caron, H., Vendramin, G. G., Guichoux, E., Buonamici, A., et al. (2013). Phylogeography of a species complex of lowland Neotropical rain forest trees (Carapa, Meliaceae). Journal of Biogeography, 40(4), 676–692.
Abstract: Aim Many tropical tree species have poorly delimited taxonomic boundaries and contain undescribed or cryptic species. We examined the genetic structure of a species complex in the tree genus Carapa in the Neotropics in order to evaluate age, geographic patterns of diversity and evolutionary relationships, and to quantify levels of introgression among currently recognized species. Location Lowland moist forests in the Guiana Shield, the Central and Western Amazon Basin, Chocó and Central America. Methods Genetic structure was analysed using seven nuclear simple sequence repeats (nuSSR), five chloroplast SSRs (cpSSR), and two chloroplast DNA (cpDNA) intergenic sequences (trnH-psbA and trnC-ycf6). Bayesian clustering analysis of the SSR data was used to infer population genetic structure and to assign 324 samples to their most likely genetic cluster. Bayesian coalescence analyses were performed on the two cpDNA markers to estimate evolutionary relationships and divergence times. Results Two genetic clusters (nuguianensis and nusurinamensis) were detected, which correspond to the Neotropical species C. guianensis (sensu latu) and C. surinamensis. Fourteen cpDNA haplotypes clustered into six haplogroups distributed between the two nuclear genetic clusters. Divergence between the haplogroups was initiated in the Miocene, with some haplotype structure evolving as recently as the Pleistocene. The absence of complete lineage sorting between the nuclear and chloroplast genomes and the presence of hybrid individuals suggest that interspecific reproductive barriers are incomplete. NuSSR diversity was highest in C. guianensis and, within C. guianensis, cpDNA diversity was highest in the Central and Western Amazon Basin. Regional genetic differentiation was strong but did not conform to an isolation-by-distance process or exhibit a phylogeographical signal. Main conclusions The biogeographical history of Neotropical Carapa appears to have been influenced by events that took place during the Neogene. Our results point to an Amazonian centre of origin and diversification of Neotropical Carapa, with subsequent migration to the Pacific coast of South America and Central America. Gene flow apparently occurs among species, and introgression events are supported by inconsistencies between chloroplast and nuclear lineage sorting. The absence of phylogeographical structure may be a result of the ineffectiveness of geographical barriers among populations and of reproductive isolation mechanisms among incipient and cryptic species in this species complex. © 2012 Blackwell Publishing Ltd.
Keywords: Amazonia; Carapa; Historical biogeography; Mahogany family; Molecular markers; Neogene diversification; Phylogeography; Quaternary diversification; Species complexes
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Lamarre, G. P. A., Amoretti, D. S., Baraloto, C., Bénéluz, F., Mesones, I., & Fine, P. V. A. (2016). Phylogenetic Overdispersion in Lepidoptera Communities of Amazonian White-sand Forests. Biotropica, 48(1), 101–109.
Abstract: In the Amazon basin and the Guiana Shield, white-sand (WS) forests are recognized as a low-resource habitat often composed by a distinct flora with many edaphic endemic plants. Small patches of nutrient-poor white-sand forests can pose a series of challenges to plants and animals. For plants, these challenges have been shown to function as strong filters that in turn drive taxonomic, functional and phylogenetic plant composition. However, very little is known about animal communities in WS forest and the effect that low-resource availability may have on higher trophic levels. Here, we investigate the diversity of both taxonomic and phylogenetic diversity of three Lepidoptera families' (Nymphalidae, Saturniidae, and Sphingidae) assemblages between low-resource (White-Sand Forest) and two adjacent high-resource habitats, terra firme clay and seasonally flooded forests. We found no clear effect of habitat type on taxonomic composition although butterfly and moth species abundance differed among the three contrasted habitats. The WS forest Lepidoptera community is significantly more phylogenetically overdispersed than expected by chance. We suggest that these low-resource habitats filter the number of plant lineages which, in turn, creates a bottom-up control structuring Lepidoptera phylogenetic structure. We recommend long-term sampling on Lepidoptera community both at larval and adult stages that may complement this study and test hypotheses linking herbivore phylogenetic structure to plant resource availability and trophic cascade theory. © 2016 The Association for Tropical Biology and Conservation.
Keywords: varillales; Amazon basin; Bottom-up; Lepidoptera composition; Moth, Nymphalidae; Phylogenetic structure
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Honorio Coronado, E. N., Dexter, K. G., Pennington, R. T., Chave, J., Lewis, S. L., Alexiades, M. N., et al. (2015). Phylogenetic diversity of Amazonian tree communities. Diversity and Distributions, 21(11), 1295–1307.
Abstract: Aim: To examine variation in the phylogenetic diversity (PD) of tree communities across geographical and environmental gradients in Amazonia. Location: Two hundred and eighty-three c. 1 ha forest inventory plots from across Amazonia. Methods: We evaluated PD as the total phylogenetic branch length across species in each plot (PDss), the mean pairwise phylogenetic distance between species (MPD), the mean nearest taxon distance (MNTD) and their equivalents standardized for species richness (ses.PDss, ses.MPD, ses.MNTD). We compared PD of tree communities growing (1) on substrates of varying geological age; and (2) in environments with varying ecophysiological barriers to growth and survival. Results: PDss is strongly positively correlated with species richness (SR), whereas MNTD has a negative correlation. Communities on geologically young- and intermediate-aged substrates (western and central Amazonia respectively) have the highest SR, and therefore the highest PDss and the lowest MNTD. We find that the youngest and oldest substrates (the latter on the Brazilian and Guiana Shields) have the highest ses.PDss and ses.MNTD. MPD and ses.MPD are strongly correlated with how evenly taxa are distributed among the three principal angiosperm clades and are both highest in western Amazonia. Meanwhile, seasonally dry tropical forest (SDTF) and forests on white sands have low PD, as evaluated by any metric. Main conclusions: High ses.PDss and ses.MNTD reflect greater lineage diversity in communities. We suggest that high ses.PDss and ses.MNTD in western Amazonia results from its favourable, easy-to-colonize environment, whereas high values in the Brazilian and Guianan Shields may be due to accumulation of lineages over a longer period of time. White-sand forests and SDTF are dominated by close relatives from fewer lineages, perhaps reflecting ecophysiological barriers that are difficult to surmount evolutionarily. Because MPD and ses.MPD do not reflect lineage diversity per se, we suggest that PDss, ses.PDss and ses.MNTD may be the most useful diversity metrics for setting large-scale conservation priorities. © 2015 John Wiley & Sons Ltd.
Keywords: Amazon basin; Eudicots; Magnoliids; Monocots; Phylogenetic diversity; Species richness
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Paine, C. E. T., Norden, N., Chave, J., Forget, P. - M., Fortunel, C., Dexter, K. G., et al. (2012). Phylogenetic density dependence and environmental filtering predict seedling mortality in a tropical forest. Ecol. Lett., 15(1), 34–41.
Abstract: Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedling's mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities. © 2011 Blackwell Publishing Ltd/CNRS.
Keywords: Community assembly; Density dependence; French Guiana; Generalised linear mixed models; Janzen-Connell hypothesis; Seedling recruitment; Species coexistence; Survival
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Lenoir, A., Boulay, R., Dejean, A., Touchard, A., & Cuvillier-Hot, V. (2016). Phthalate pollution in an Amazonian rainforest. Environmental Science and Pollution Research, 23(16), 16865–16872.
Abstract: Phthalates are ubiquitous contaminants and endocrine-disrupting chemicals that can become trapped in the cuticles of insects, including ants which were recognized as good bioindicators for such pollution. Because phthalates have been noted in developed countries and because they also have been found in the Arctic, a region isolated from direct anthropogenic influence, we hypothesized that they are widespread. So, we looked for their presence on the cuticle of ants gathered from isolated areas of the Amazonian rainforest and along an anthropogenic gradient of pollution (rainforest vs. road sides vs. cities in French Guiana). Phthalate pollution (mainly di(2-ethylhexyl) phthalate (DEHP)) was higher on ants gathered in cities and along road sides than on those collected in the pristine rainforest, indicating that it follows a human-mediated gradient of disturbance related to the use of plastics and many other products that contain phthalates in urban zones. Their presence varied with the ant species; the cuticle of Solenopsis saevissima traps higher amount of phthalates than that of compared species. However, the presence of phthalates in isolated areas of pristine rainforests suggests that they are associated both with atmospheric particles and in gaseous form and are transported over long distances by wind, resulting in a worldwide diffusion. These findings suggest that there is no such thing as a “pristine” zone.
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