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Almeras, T., & Fournier, M. (2009). Biomechanical design and long-term stability of trees: Morphological and wood traits involved in the balance between weight increase and the gravitropic reaction. J. Theor. Biol., 256(3), 370–381.
Abstract: Studies on tree biomechanical design usually focus on stem stiffness, resistance to breakage or uprooting, and elastic stability. Here we consider another biomechanical constraint related to the interaction between growth and gravity. Because stems are slender structures and are never perfectly symmetric, the increase in tree mass always causes bending movements. Given the current mechanical design of trees, integration of these movements over time would ultimately lead to a weeping habit unless some gravitropic correction occurs. This correction is achieved by asymmetric internal forces induced during the maturation of new wood. The long-term stability of a growing stem therefore depends on how the gravitropic correction that is generated by diameter growth balances the disturbance due to increasing self weight. General mechanical formulations based on beam theory are proposed to model these phenomena. The rates of disturbance and correction associated with a growth increment are deduced and expressed as a function of elementary traits of stem morphology, cross-section anatomy and wood properties. Evaluation of these traits using previously published data shows that the balance between the correction and the disturbance strongly depends on the efficiency of the gravitropic correction, which depends on the asymmetry of wood maturation strain, eccentric growth, and gradients in wood stiffness. By combining disturbance and correction rates, the gravitropic performance indicates the dynamics of stem bending during growth. It depends on stem biomechanical traits and dimensions. By analyzing dimensional effects, we show that the necessity for gravitropic correction might constrain stem allometric growth in the long-term. This constraint is compared to the requirement for elastic stability, showing that gravitropic performance limits the increase in height of tilted stem and branches. The performance of this function may thus limit the slenderness and lean of stems, and therefore the ability of the tree to capture light in a heterogeneous environment. (c) 2008 Elsevier Ltd. All rights reserved.
Keywords: Mechanical design; Gravitropism; Bending stresses; Allometry; Reaction wood
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Casella, T. M., Eparvier, V., Mandavid, H., Bendelac, A., Odonne, G., Dayan, L., et al. (2013). Antimicrobial and cytotoxic secondary metabolites from tropical leaf endophytes: Isolation of antibacterial agent pyrrocidine C from Lewia infectoria SNB-GTC2402. Phytochemistry, 96, 370–377.
Abstract: Because of the symbiotic nature of endophytes, this survey aims to investigate the probability of discovering antibacterial, antifungal and cytotoxic activities in leaf endophytic microbes. We isolated 138 cultivable microbes (121 fungi, 3 bacteria and 14 unidentified or unknown microbes) from 24 plant species, a significant relative proportion of which exhibited antifungal and cytotoxic potential against Candida albicans ATCC 10213 and the human cell lines KB (uterine cervical carcinoma), MDA-MB-435 (melanoma), and MRC5 (normal human lung fibroblasts). Three active fungal extracts were fractionated, resulting in the isolation of eight compounds. Seven had been described in the literature including the following: acremonisol A, semicochliodinol A, cochliodinol, griseofulvin, pyrenocin A, novae zelandin A and alterperylenol. A previously unreported compound named pyrrocidine C was isolated from Lewia infectoria SNB-GTC2402 and identified by spectroscopic analysis. As in pyrrocidines A and B, this compound is a cis-substituted decahydrofluorene with a quaternary carbon at C-5 and opposite stereochemistry at C-8 corresponding to C-6 of pyrrocidines A and B.© 2013 Elsevier Ltd. All rights reserved.
Keywords: Antimicrobials; Cytotoxic metabolites; Functional chemodiversity; Leaf endophytes; Lewia; Pyrrocidine C
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Scotti-Saintagne, C., Bertocchi, E., Barreneche, T., Kremer, A., & Plomion, C. (2005). Quantitative trait loci mapping for vegetative propagation in pedunculate oak. Ann. For. Sci., 62(4), 369–374.
Abstract: Vegetative propagation is one of the main methods used for the deployment of improved genetic forest tree species. The objective of this paper was to study the genetic architecture of vegetative propagation by detecting Quantitative Trait Loci (QTL) in pedunculate oak ( Quercus robur). The mapping population consisted on an F-1 family of 278 offspring. Assessment of rooting ability over three years permitted the detection of 10 QTLs explaining between 4.4 and 13.8% of phenotypic variance, of which the two strongest were stable across years. Ongoing genomics programs in trees and in Arabidopsis are starting to shed light on the nature of the underlying genes.
Keywords: vegetative propagation; QTL; Quercus robur
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Orivel, J., Lambs, L., Male, P. J. G., Leroy, C., Grangier, J., Otto, T., et al. (2011). Dynamics of the association between a long-lived understory myrmecophyte and its specific associated ants. Oecologia, 165(2), 369–376.
Abstract: Myrmecophytic symbioses are widespread in tropical ecosystems and their diversity makes them useful tools for understanding the origin and evolution of mutualisms. Obligate ant-plants, or myrmecophytes, provide a nesting place, and, often, food to a limited number of plant-ant species. In exchange, plant-ants protect their host plants from herbivores, competitors and pathogens, and can provide them with nutrients. Although most studies to date have highlighted a similar global pattern of interactions in these systems, little is known about the temporal structuring and dynamics of most of these associations. In this study we focused on the association between the understory myrmecophyte Hirtella physophora (Chrysobalanaceae) and its obligate ant partner Allomerus decemarticulatus (Myrmicinae). An examination of the life histories and growth rates of both partners demonstrated that this plant species has a much longer lifespan (up to about 350 years) than its associated ant colonies (up to about 21 years). The size of the ant colonies and their reproductive success were strongly limited by the available nesting space provided by the host plants. Moreover, the resident ants positively affected the vegetative growth of their host plant, but had a negative effect on its reproduction by reducing the number of flowers and fruits by more than 50%. Altogether our results are important to understanding the evolutionary dynamics of ant-plant symbioses. The highly specialized interaction between long-lived plants and ants with a shorter lifespan produces an asymmetry in the evolutionary rates of the interaction which, in return, can affect the degree to which the interests of the two partners converge.
Keywords: Allomerus decemarticulatus; Hirtella physophora; Lifespan; Mutualism; Myrmecophyte
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Taureau, F., Robin, M., Proisy, C., Fromard, F., Imbert, D., & Debaine, F. (2019). Mapping the mangrove forest canopy using spectral unmixing of very high spatial resolution satellite images. Remote Sens., 11(3), 367.
Abstract: Despite the lowtree diversity and scarcity of the understory vegetation, the high morphological plasticity of mangrove trees induces, at the stand level, a very large variability of forest structures that need to be mapped for assessing the functioning of such complex ecosystems. Fully constrained linear spectral unmixing (FCLSU) of very high spatial resolution (VHSR) multispectral images was tested to fine-scale map mangrove zonations in terms of horizontal variation of forest structure. The study was carried out on three Pleiades-1A satellite images covering French island territories located in the Atlantic, Indian, and Pacific Oceans, namely Guadeloupe, Mayotte, and New Caledonia archipelagos. In each image, FCLSU was trained from the delineation of areas exclusively related to four components including either pure vegetation, soil (ferns included), water, or shadows. It was then applied to the whole mangrove cover imaged for each island and yielded the respective contributions of those four components for each image pixel. On the forest stand scale, the results interestingly indicated a close correlation between FCLSU-derived vegetation fractions and canopy closure estimated from hemispherical photographs R 2 = 0.95) and a weak relation with the Normalized Difference Vegetation Index (R 2 = 0.29). Classification of these fractions also offered the opportunity to detect and map horizontal patterns of mangrove structure in a given site. K-means classifications of fraction indeed showed a global view of mangrove structure organization in the three sites, complementary to the outputs obtained from spectral data analysis. Our findings suggest that the pixel intensity decomposition applied to VHSR multispectral satellite images can be a simple but valuable approach for (i) mangrove canopy monitoring and (ii) mangrove forest structure analysis in the perspective of assessing mangrove dynamics and productivity. As with Lidar-based surveys, these potential new mapping capabilities deserve further physically based interpretation of sunlight scattering mechanisms within forest canopy. © 2019 by the authors.
Keywords: Forest structure; Guadeloupe; Hemispherical photographs; Mangrove; Mayotte; New Caledonia; Remote sensing; Image resolution; Photography; Photomapping; Pixels; Remote sensing; Satellites; Vegetation; Forest structure; Guadeloupe; Hemispherical photographs; Mangrove; Mayotte; New Caledonia; Forestry
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Rockwell, C., Kainer, K. A., Marcondes, N., & Baraloto, C. (2007). Ecological limitations of reduced-impact logging at the smallholder scale. For. Ecol. Manage., 238(1-3), 365–374.
Abstract: Reduced-impact logging (RIL) has many demonstrated benefits to the industrial logging operations for which they were developed. It is less clear whether these gains remain consistent in smallholder forest systems that increasingly play an important role in global conservation and that target a broader suite of outputs in their management schemes. We evaluate potential ecological consequences of five RIL components (pre-harvest inventories, harvest intensity, cutting cycles, skid trail planning, and liana cutting) when applied to small-scale operations in the Brazilian Amazon and provide suggestions for modifications to RIL guidelines for smallholder systems. Rapid assessment inventories of the entire landholding should be a part of crop tree selection to minimize inbreeding and recruitment failure. Additionally, while community-based taxonomists accurately identify species to common names, botanical samples must be verified with herbarium specimens to avoid market and ecological problems when multiple species share a single common name. We advocate that smallholder managers move beyond an emphasis on RIL guidelines, while still incorporating its basic tenets into practical application. Based on our analysis, this would include evaluating benefits of particular RIL components and assessing potential advantages that smallholders have over industrial operations. We suggest incorporating anthropogenically-generated forest patches of varying sizes and successional stages into a more formalized management system, incorporating and expanding on traditional ecological knowledge acquired over generations, and integrating enrichment plantings and tending of regeneration. (c) 2006 Published by Elsevier B.V.
Keywords: community forest management; forest inventories; liana cutting; sustained yield; timber management; tropical forest conservation
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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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Sist, P., Fimbel, R., Sheil, D., Nasi, R., & Chevallier, M. H. (2003). Towards sustainable management of mixed dipterocarp forests of South-east Asia: moving beyond minimum diameter cutting limits. Environmental Conservation, 30(4), 364–374.
Abstract: Selective logging applied in tropical forests is based on one universal criterion: a minimum diameter cutting limit for all commercial timber species. Minimum diameter cutting limits in mixed dipterocarp forests of the Malesia region lead to high felling intensities (10-20+ trees ha(-1)). Such extraction rates create massive stand damage (> 50% of the remaining tree population), which has a negative impact on the regeneration and growth of many harvested dipterocarp, species. As such, the minimum diameter cutting limit approach is seldom compatible with sustainable forest management. Where basic ecological characteristics of the commercial species are considered in timber harvesting prescriptions, mixed dipterocarp, forests appear capable of sustained timber yields, habitat conservation, and providing other goods and services. This paper first presents the main silvicultural systems developed in mixed dipterocarp, forests of Western Malesia and then reviews current knowledge of dipterocarp, biology to finally develop guidelines aimed at improving the ecological sustainability of production forests of Western Malesia. These guidelines, a pragmatic reflection of science and 'best guess' judgement, include: (1) integration of reduced-impact logging practices into normal management operations; (2) cutting of eight trees ha(-1) or less (with a felling cycle of 40-60 years to be determined according to local conditions); (3) defining minimum diameter cutting limits according to the structure, density and diameter at reproduction of target species; (4) avoiding harvesting species with less than one adult tree ha(-1) (diameter at breast height [dbh] greater than or equal to 50 cm over an area of 50-100 ha); (5) minimizing the size and connectivity of gaps (< 600 m(2) whenever possible); (6) refraining from treatments such as understorey clearing; and (7) providing explicit protection for key forest species and the ecological processes they perform. Further refinement is encouraged to allow for local conditions, and for other forest types.
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Foucaud, J., Orivel, J., Loiseau, A., Delabie, J. H. C., Jourdan, H., Konghouleux, D., et al. (2010). Worldwide invasion by the little fire ant: routes of introduction and eco-evolutionary pathways. Evol. Appl., 3(4), 363–374.
Abstract: Biological invasions are generally thought to occur after human aided migration to a new range. However, human activities prior to migration may also play a role. We studied here the evolutionary genetics of introduced populations of the invasive ant Wasmannia auropunctata at a worldwide scale. Using microsatellite markers, we reconstructed the main routes of introduction of the species. We found three main routes of introduction, each of them strongly associated to human history and trading routes. We also demonstrate the overwhelming occurrence of male and female clonality in introduced populations of W. auropunctata, and suggest that this particular reproduction system is under selection in human-modified habitats. Together with previous researches focused on native populations, our results suggest that invasive clonal populations may have evolved within human modified habitats in the native range, and spread further from there. The evolutionarily most parsimonious scenario for the emergence of invasive populations of the little fire ant might thus be a two-step process. The W. auropunctata case illustrates the central role of humans in biological change, not only due to changes in migration patterns, but also in selective pressures over species.
Keywords: biological invasion; introduction routes; parthenogenesis; reproduction system; Wasmannia auropunctata
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Rifflet, A., Gavalda, S., Téné, N., Orivel, J., Leprince, J., Guilhaudis, L., et al. (2012). Identification and characterization of a novel antimicrobial peptide from the venom of the ant Tetramorium bicarinatum. Peptides, 38(2), 363–370.
Abstract: A novel antimicrobial peptide, named Bicarinalin, has been isolated from the venom of the ant Tetramorium bicarinatum. Its amino acid sequence has been determined by de novo sequencing using mass spectrometry and by Edman degradation. Bicarinalin contained 20 amino acid residues and was C-terminally amidated as the majority of antimicrobial peptides isolated to date from insect venoms. Interestingly, this peptide had a linear structure and exhibited no meaningful similarity with any known peptides. Antibacterial activities against Staphylococcus aureus and S. xylosus strains were evaluated using a synthetic replicate. Bicarinalin had a potent and broad antibacterial activity of the same magnitude as Melittin and other hymenopteran antimicrobial peptides such as Pilosulin or Defensin. Moreover, this antimicrobial peptide has a weak hemolytic activity compared to Melittin on erythrocytes, suggesting potential for development into an anti-infective agent for use against emerging antibiotic-resistant pathogens. © 2012 Elsevier Inc.
Keywords: Amp; Ant venom; Antibacterial peptide; Bicarinalin; Esi-Ms/Ms; Staphylococcus; Tetramorium bicarinatum
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