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Cachet, N., Hoakwie, F., Bertani, S., Bourdy, G., Deharo, E., Stien, D., et al. (2009). Antimalarial Activity of Simalikalactone E, a New Quassinoid from Quassia amara L. (Simaroubaceae). Antimicrob. Agents Chemother., 53(10), 4393–4398.
Abstract: 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.
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Seipke, R. F., Barke, J., Ruiz-Gonzalez, M. X., Orivel, J., Yu, D. W., & Hutchings, M. I. (2012). Fungus-growing Allomerus ants are associated with antibiotic-producing actinobacteria. Antonie Van Leeuwenhoek Int. J. Gen. Mol. Microbiol., 101(2), 443–447.
Abstract: Fungus-growing attine ants use natural-product antibiotics produced by mutualist actinobacteria as 'weedkillers' in their fungal gardens. Here we report for the first time that fungus-growing Allomerus ants, which lie outside the tribe Attini, are associated with antifungal-producing actinobacteria, which offer them protection against non-cultivar fungi isolated from their ant-plants. © 2011 Springer Science+Business Media B.V.
Keywords: Allomerus ants; Amycolatopsis; Ant-bacteria symbioses; Fungus-growing ants; Insect fungiculture; Streptomyces
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Schimann, H., Joffre, R., Roggy, J. C., Lensi, R., & Domenach, A. M. (2007). Evaluation of the recovery of microbial functions during soil restoration using near-infrared spectroscopy. Appl. Soil Ecol., 37(3), 223–232.
Abstract: Microbial-based indicators, such as C and N contents or microbial functions involved in C and N cycles, are currently used to describe the status of soils in disturbed areas. Microbial functions are more accurate indicators but their measurement for studies at the ecosystem level remains problematical because of the huge spatial variability of these processes and, consequently, of the large number of soil samples which must be analyzed. Our goal was to test the capacity of near-infrared reflectance spectroscopy (NIRS) to predict respiration and denitrification but also carbon and nitrogen contents of soils submitted to various procedures of restoration. To achieve this objective, we took advantage of an experiment conducted on a reforestation system established after open-cast gold mining in French Guiana. In this experimental station, plantations of various ages and various soil textures were at our disposal. Our results showed that both plantations and soil texture had a strong impact on the recovery of soil functioning: carbon and nitrogen contents, respiration and denitrification increased with age of plantation and clay content. Calibrations were performed between spectral data and microbial-based indicators using partial least squares regression (PLS). The results showed that C and N contents were accurately predicted. Microbial functions were less precisely predicted with results more accurate on clayey soils than on sandy soils. In clayey soils, perturbed or restored soils and the year of plantation were discriminated very efficiently through principal component analyses of spectral signatures (over 80% of variance explained on the first two axes). Near-infrared spectroscopy may thus be extended to the prediction of functional soil parameters, but the capacity of this method must be strengthened by expending the databases with other soils in other contexts. The possibility of using NIRS provides many opportunities for understanding both the temporal dynamics and the spatial variability of the recovery of key microbial functions during soil restoration. (c) 2007 Elsevier B.V. All rights reserved.
Keywords: NIRS; microbial activities; respiration; denitrification; carbon; nitrogen; soil functioning; restoration
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Herault, B., & Honnay, O. (2007). Using life-history traits to achieve a functional classification of habitats. Appl. Veg. Sci., 10(1), 73–80.
Abstract: Question: To establish a habitat classification based on functional group co-occurrence that may help the drawing up of conservation plans. Location: Riverine forest fragments in the Grand-duche de Luxembourg, Europe. Methods: Forest fragments were surveyed for their abundance of vascular plants. These were clustered into emergent groups according to 14 life-traits related to plant dispersal, establishment and persistence. Forest fragments were classified according to similar distribution of the identified emergent groups. Environmental factors were related to the emergent group richness in each forest type using generalized linear models. Results: Contrary to former species centred classifications, only two groups of forests, each with clearly different emergent group composition and conservation requirements, were detected: (1) swamp forests characterized by anemogamous perennials, annuals and hydrochorous perennials and (2) moist forests characterized by barochorous perennials, small geophytes and zoochorous phanerophytes. From a conservation point of view, priority should be given to large swamp forest with intact flooding regimes. This is in accordance with the high wind and water dispersal capacities of their typical emergent groups. For the moist forests, conservation priorities should be high forest connectivity and historical continuity since dispersal and establishment of their characteristic emergent groups are highly limited. Conclusions: The described methodology, situated at an intermediate integration level between the individual species and whole community descriptors, takes advantage of both conservation plans built for single species and the synthetic power of broad ecological measures.
Keywords: forest connectivity; functional group; habitat typology; land-use history; riverine forest; species functional unity
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Sist, P., Rutishauser, E., Peña-Claros, M., Shenkin, A., Herault, B., Blanc, L., et al. (2015). The Tropical managed forests Observatory: A research network addressing the future of tropical logged forests. Appl. Veg. Sci., 18(1), 171–174.
Abstract: While attention on logging in the tropics has been increasing, studies on the long-term effects of silviculture on forest dynamics and ecology remain scare and spatially limited. Indeed, most of our knowledge on tropical forests arises from studies carried out in undisturbed tropical forests. This bias is problematic given that logged and disturbed tropical forests are now covering a larger area than the so-called primary forests. A new network of permanent sample plots in logged forests, the Tropical managed Forests Observatory (TmFO), aims to fill this gap by providing unprecedented opportunities to examine long-term data on the resilience of logged tropical forests at regional and global scales. TmFO currently includes 24 experimental sites distributed across three tropical regions, with a total of 490 permanent plots and 921 ha of forest inventories. To improve our knowledge of the resilience of tropical logged forests, 20 research institutes are now collaborating on studies on the effects of logging on forest structure, productivity, biodiversity and carbon fluxes at large spatial and temporal scales. These studies are carried out in the Tropical managed Forests Observatory (TmFO), an international network including 24 sites and 490 permanent sample plots across South America, Africa and South East Asia.
Keywords: Biodiversity; Carbon cycle; Climate change; Ecosystem resilience; Logging; Silviculture; Tropical forests; Tropical managed forests Observatory
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Roux, O., Vantaux, A., Petitclerc, F., Orivel, J., Dejean, A., & Billen, J. (2017). Structural adaptations and mechanism of reflex bleeding in the larvae of the myrmecophilous ladybird Diomus thoracicus. Arthropod Structure and Development, 46(4), 529–536.
Abstract: Reflex bleeding is an effective defensive mechanism against predators. When attacked, some insects emit hemolymph, which coagulates, quickly entangling their aggressor. Bleeding occurs at weak intersegmental membranes or through dedicated organs, which can be associated or not with glandular cells. Here, we describe the behavior and morphological structures involved in reflex bleeding in the larvae of the ladybird, Diomus thoracicus, which are intranidal parasites of the ant Wasmannia auropunctata. The larvae are tolerated by the ants thanks to odor mimicry, but some rare aggressive ant behaviors were observed that trigger reflex bleeding both at a pair of thoracic tubercles and a pair of posterodorsal abdominal humps. No glandular structure was found in association with these emission points, which suggests that the material emitted was hemolymph only. A 3D reconstruction suggested that reflex bleeding seems to be controlled by muscles whose contraction increases the internal hydrostatic pressure and pushes the hemolymph into a funnel-like structure with an opening to the outside. In D. thoracicus, the morphological structures involved in reflex bleeding are among the most complex and prominent described to date. © 2017 Elsevier Ltd
Keywords: 3D reconstruction; Coccinellidae; Myrmecophagous insect; Reflex bleeding; Ultrastructure
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Revel, N., Alvarez, N., Gibernau, M., & Espíndola, A. (2012). Investigating the relationship between pollination strategies and the size-advantage model in zoophilous plants using the reproductive biology of Arum cylindraceum and other European Arum species as case studies. Arthropod-Plant Interact., 6(1), 35–44.
Abstract: The size-advantage model (SAM) explains the temporal variation of energetic investment on reproductive structures (i. e. male and female gametes and reproductive organs) in long-lived hermaphroditic plants and animals. It proposes that an increase in the resources available to an organism induces a higher relative investment on the most energetically costly sexual structures. In plants, pollination interactions are known to play an important role in the evolution of floral features. Because the SAM directly concerns flower characters, pollinators are expected to have a strong influence on the application of the model. This hypothesis, however, has never been tested. Here, we investigate whether the identity and diversity of pollinators can be used as a proxy to predict the application of the SAM in exclusive zoophilous plants. We present a new approach to unravel the dynamics of the model and test it on several widespread Arum (Araceae) species. By identifying the species composition, abundance and spatial variation of arthropods trapped in inflorescences, we show that some species (i. e. A. cylindraceum and A. italicum) display a generalist reproductive strategy, relying on the exploitation of a low number of dipterans, in contrast to the pattern seen in the specialist A. maculatum (pollinated specifically by two fly species only). Based on the model presented here, the application of the SAM is predicted for the first two and not expected in the latter species, those predictions being further confirmed by allometric measures. We here demonstrate that while an increase in the female zone occurs in larger inflorescences of generalist species, this does not happen in species demonstrating specific pollinators. This is the first time that this theory is both proposed and empirically tested in zoophilous plants. Its overall biological importance is discussed through its application in other non-Arum systems. © 2011 Springer Science+Business Media B.V.
Keywords: Araceae; Flower evolution; Plant-insect interactions; Reproductive strategy; Sex allocation
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Malé, P. - J. G., Leroy, C., Lusignan, L., Petitclerc, F., Quilichini, A., & Orivel, J. (2015). The reproductive biology of the myrmecophyte, Hirtella physophora, and the limitation of negative interactions between pollinators and ants. Arthropod-Plant Interactions, 9(1), 23–31.
Abstract: Myrmecophytism occurs in plants that offer ants a nesting space and, often, food rewards in exchange for protection from predators and competitors. Such biotic protection by ants can, however, interfere with the activity of pollinators leading to potential negative consequences for the plant’s reproduction. In this study, we focused on the association between the understory myrmecophyte, Hirtella physophora (Chrysobalanaceae), and its obligate ant partner, Allomerus decemarticulatus (Myrmicinae). We investigated the reproductive biology of H. physophora and the putative mechanisms that may limit ant–pollinator conflict. Our results show that H. physophora is an obligate outcrosser, self-incompatible, and potentially insect-pollinated species. The reproduction of H. physophora relies entirely on pollen transfer by pollinators that are likely quite specific. Potential interference between flower-visiting insects during pollination may also be lessened by a spatial and temporal segregation of ant and pollinator activities, thus enabling pollen transfer and fruit production. © 2014, Springer Science+Business Media Dordrecht.
Keywords: Ant-plant; Ant–pollinator interactions; Floral structure and display; Plant reproductive biology; Spatial and temporal segregation
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Buckland, S. T., Yuan, Y., & Marcon, E. (2017). Measuring temporal trends in biodiversity. AStA Advances in Statistical Analysis, 101(4), 461–474.
Abstract: In 2002, nearly 200 nations signed up to the 2010 target of the Convention for Biological Diversity, ‘to significantly reduce the rate of biodiversity loss by 2010’. To assess whether the target was met, it became necessary to quantify temporal trends in measures of diversity. This resulted in a marked shift in focus for biodiversity measurement. We explore the developments in measuring biodiversity that was prompted by the 2010 target. We consider measures based on species proportions, and also explain why a geometric mean of relative abundance estimates was preferred to such measures for assessing progress towards the target. We look at the use of diversity profiles, and consider how species similarity can be incorporated into diversity measures. We also discuss measures of turnover that can be used to quantify shifts in community composition arising, for example, from climate change. © 2017, The Author(s).
Keywords: Biodiversity measures; Diversity profiles; Geometric mean; Species similarity; Turnover measures
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Foken, T., Meixner, F. X., Falge, E., Zetzsch, C., Serafimovich, A., Bargsten, A., et al. (2012). Coupling processes and exchange of energy and reactive and non-reactive trace gases at a forest site – results of the EGER experiment. Atmos. Chem. Phys., 12(4), 1923–1950.
Abstract: To investigate the energy, matter and reactive and non-reactive trace gas exchange between the atmosphere and a spruce forest in the German mountain region, two intensive measuring periods were conducted at the FLUXNET site DE-Bay (Waldstein-Weidenbrunnen) in September/October 2007 and June/July 2008. They were part of the project “ExchanGE processes in mountainous Regions” (EGER). Beyond a brief description of the experiment, the main focus of the paper concerns the coupling between the trunk space, the canopy and the above-canopy atmosphere. Therefore, relevant coherent structures were analyzed for different in- and above canopy layers, coupling between layers was classified according to already published procedures, and gradients and fluxes of meteorological quantities as well as concentrations of non-reactive and reactive trace compounds have been sorted along the coupling classes. Only in the case of a fully coupled system, it could be shown, that fluxes measured above the canopy are related to gradients between the canopy and the above-canopy atmosphere. Temporal changes of concentration differences between top of canopy and the forest floor, particularly those of reactive trace gases (NO, NO2, O-3, and HONO) could only be interpreted on the basis of the coupling stage. Consequently, only concurrent and vertically resolved measurements of micrometeorological (turbulence) quantities and fluxes (gradients) of trace compounds will lead to a better understanding of the forest-atmosphere interaction.
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