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Bremaud, I., Cabrolier, P., Gril, J., Clair, B., Gerard, J., Minato, K., et al. (2010). Identification of anisotropic vibrational properties of Padauk wood with interlocked grain. Wood Sci. Technol., 44(3), 355–367.
Abstract: Grain deviations and high extractives content are common features of many tropical woods. This study aimed at clarifying their respective impact on vibrational properties, referring to African Padauk (Pterocarpus soyauxii Taub.), a species selected for its interlocked grain, high extractives content and uses in xylophones. Specimens were cut parallel to the trunk axis (L), and local variations in grain angle (GA), microfibril angle (MFA), specific Young's modulus (E' (L) /rho, where rho stands for the density) and damping coefficient (tan delta(L)) were measured. GA dependence was analysed by a mechanical model which allowed to identify the specific Young's modulus (E'(3)/rho) and shear modulus (G'/rho) along the grain (3) as well as their corresponding damping coefficients (tan delta(3), tan delta(G)). This analysis was done for native and then for extracted wood. Interlocked grain resulted in 0-25A degrees GA and in variations of a factor 2 in E'(L)/rho and tan delta(L). Along the grain, Padauk wood was characterized, when compared to typical hardwoods, by a somewhat lower E'(3)/rho and elastic anisotropy (E'/G'), due to a wide microfibril angle plus a small weight effect of extracts, and a very low tan delta(3) and moderate damping anisotropy (tan delta(G)/tan delta(3)). Extraction affected mechanical parameters in the order: tan delta(3) a parts per thousand tan delta(G) > G'/rho > > E'(3)/rho. That is, extractives' effects were nearly isotropic on damping but clearly anisotropic on storage moduli.
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Fouquet, A., Ledoux, J. - B., Dubut, V., Noonan, B. P., & Scotti, I. (2012). The interplay of dispersal limitation, rivers, and historical events shapes the genetic structure of an Amazonian frog. Biol. J. Linn. Soc., 106(2), 356–373.
Abstract: Disentangling the impact of landscape features such as rivers and historical events on dispersal is a challenging but necessary task to gain a comprehensive picture of the evolution of diverse biota such as that found in Amazonia. Adenomera andreae, a small, territorial, terrestrial frog species of the Amazonian forest represents a good model for such studies. We combined cytochromeb sequences with 12 microsatellites to investigate the genetic structure at two contrasted spatial scales in French Guiana: along a ∼6-km transect, to evaluate dispersal ability, and between paired bank populations along a ∼65-km stretch of the Approuague river, to test the effect of rivers as barriers to dispersal. We observed significant spatial genetic structure between individuals at a remarkably small geographical scale, and conclude that the species has a restricted dispersal ability that is probably tied to its life-history traits. Mitochondrial and microsatellite data also indicate a high level of differentiation among populations on opposite banks of the river, and, in some cases, among populations on the same riverbank. These results suggest that the observed population structure in A.andreae is the result of restricted dispersal abilities combined with the action of rivers and Quaternary population isolation. Given that Amazonia hosts a great portion of anurans, as well as other small vertebrates, that display life-history traits comparable with A.andreae, we argue that our analyses provide new insights into the complex interactions among evolutionary processes shaping Amazonian biodiversity. © 2012 The Linnean Society of London.
Keywords: Amazonia; Amphibian; Gene flow; Microsatellites; Mitochondrial DNA; Spatial genetic structure
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Vincent, G., Molino, J. F., Marescot, L., Barkaoui, K., Sabatier, D., Freycon, V., et al. (2011). The relative importance of dispersal limitation and habitat preference in shaping spatial distribution of saplings in a tropical moist forest: a case study along a combination of hydromorphic and canopy disturbance gradients. Ann. For. Sci., 68(2), 357–370.
Abstract: Various processes contribute to shaping the local assemblage of species in hyperdiverse tropical forest. The relative contribution of environmental factors and dispersal limitation in determining the spatial distribution of saplings at local scale is unclear. We examined two types of environmental factors: (a) soil type reflecting drainage regime and (b) past logging damages reflecting light regime in a neotropical moist forest site. We used a logistic model to predict presence or absence of a given species in a network of elementary small plots. The effect of mapped environmental factors and a spatial correlation term were jointly estimated providing a direct measure of the relative role of habitat specialisation and dispersal limitation. At community level, dispersal limitation was the most important determinant of species absence at local scale. The two environmental factors examined played a balanced role. Different species however showed different degrees of dispersal limitation and habitat specialisation. The distribution of a large proportion of species-the majority of the most abundant species-was significantly affected by at least one environmental factor. We provide a ranking of 49 species sensitive to canopy disturbance (from shade specialist to pioneer) and 41 species affected by seasonal flooding (either positively or negatively).
Keywords: Species assemblage; Dispersal limitation; Tropical moist forest; Niche
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Zalamea, P. - C., Sarmiento, C., Stevenson, P. R., Rodríguez, M., Nicolini, E., & Heuret, P. (2013). Effect of rainfall seasonality on the growth of Cecropia sciadophylla: Intra-annual variation in leaf production and node length. J. Trop. Ecol., 29(4), 361–365.
Abstract: Patterns of leaf production and leaf fall directly influence leaf area index and forest productivity. Here, we focused on Cecropia sciadophylla individuals inhabiting the extremes of the gradient in seasonality in rainfall at which C. sciadophylla occurs. In Colombia and French Guiana we compared the intra-annual variation in leaf production as well as the intra-annual fluctuation in internode length on a total of 69 saplings ranging in size from 1 to 2 m. The mean rate of leaf production was ~2 leaves mo -1 in both populations, and the rate of leaf production was constant throughout the year. Our results showed monthly variation in internode length and the number of live leaves per sapling in the seasonal habitat and variation only in internode length in the everwet habitat. Because the rate of leaf production is constant at both localities, the difference in number of live leaves per sapling at the seasonal site must reflect seasonal variation in leaf life span. We show that in Cecropia, internode length can serve as an indicator of precipitation seasonality. Finally an open question is whether leaf production in other pioneer species is also independent of climatic seasonal cues. This information could allow us to link growth and climate of secondary forest species and better understand how past and future climate can affect plant growth trajectories. © Cambridge University Press 2013.
Keywords: leaf phenology; Neotropics; pioneer plants; plant growth; plant morphology; rainfall seasonality; Urticaceae
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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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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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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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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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