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Svensk, M.; Coste, S.; Gérard, B.; Gril, E.; Julien, F.; Maillard, P.; Stahl, C.; Leroy, C. |
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Title |
Drought effects on resource partition and conservation among leaf ontogenetic stages in epiphytic tank bromeliads |
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Journal Article |
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Year |
2020 |
Publication |
Physiologia Plantarum |
Abbreviated Journal |
Physiol. Plant. |
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Volume |
170 |
Issue |
4 |
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488-507 |
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Keywords |
chlorophyll; nitrogen; water; Bromeliaceae; drought; metabolism; photosynthesis; plant leaf; Bromeliaceae; Chlorophyll; Droughts; Nitrogen; Photosynthesis; Plant Leaves; Water |
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Studying the response to drought stress of keystone epiphytes such as tank bromeliads is essential to better understand their resistance capacity to future climate change. The objective was to test whether there is any variation in the carbon, water and nutrient status among different leaf ontogenetic stages in a bromeliad rosette subjected to a gradient of drought stress. We used a semi-controlled experiment consisting in a gradient of water shortage in Aechmea aquilega and Lutheria splendens. For each bromeliad and drought treatment, three leaves were collected based on their position in the rosette and several functional traits related to water and nutrient status, and carbon metabolism were measured. We found that water status traits (relative water content, leaf succulence, osmotic and midday water potentials) and carbon metabolism traits (carbon assimilation, maximum quantum yield of photosystem II, chlorophyll and starch contents) decreased with increasing drought stress, while leaf soluble sugars and carbon, nitrogen and phosphorus contents remained unchanged. The different leaf ontogenetic stages showed only marginal variations when subjected to a gradient of drought. Resources were not reallocated between different leaf ontogenetic stages but we found a reallocation of soluble sugars from leaf starch reserves to the root system. Both species were capable of metabolic and physiological adjustments in response to drought. Overall, this study advances our understanding of the resistance of bromeliads faced with increasing drought stress and paves the way for in-depth reflection on their strategies to cope with water shortage. © 2020 Scandinavian Plant Physiology Society |
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Laboratoire Ecologie Fonctionnelle et Environnement, Université de Toulouse, CNRS, Toulouse, 31062, France |
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Blackwell Publishing Ltd |
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00319317 (Issn) |
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PDF trop gros voir la documentaliste – merci |
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EcoFoG @ webmaster @ |
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943 |
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Traissac, S.; Pascal, J.-P. |
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Birth and life of tree aggregates in tropical forest: Hypotheses on population dynamics of an aggregated shade-tolerant species |
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Journal Article |
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Year |
2014 |
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Journal of Vegetation Science |
Abbreviated Journal |
J. Veg. Sci. |
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25 |
Issue |
2 |
Pages |
491-502 |
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Keywords |
Clusters; Colonization strategy; Janzen-Connell; Spatial analysis; Spatial pattern; Vouacapoua americana |
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Questions: Several studies have described aggregated spatial patterns in tropical tree species. This study investigates aggregate dynamics of Vouacapoua americana (Aublet), a climax species whose spatial pattern is not simply related to light and soil conditions or to its short seed dispersal range. Location: Two rain forest sites: Nouragues and Paracou, in the Guiana Shield. Methods: We described the spatial pattern of tree locations and spatial autocorrelation of tree diameters, using statistics derived from Ripley's K. We particularly used methods to define analysis subplots according to local density or local mean diameter. We investigated relationships between spatial distributions of adults and saplings. Results: At both sites, populations of Vouacapoua demonstrated several nested levels of aggregation. Tree diameters were spatially autocorrelated, revealing the existence of clusters with similar diameters. In the largest aggregates, tree diameters declined from the centre to the edge. Regeneration was aggregated and occurred mainly at cluster edges and around rare isolated trees, and sapling densities and basal area of adults were negatively correlated. We show that long-distance dispersal events are rare. Conclusions: Environmental factors and seed dispersal only explain part of the observed spatial patterns. We provide two main hypotheses about Vouacapoua population dynamics. First, the lack of regeneration in aggregate centres results in the ageing of existing aggregates. We suggest that this lack of recruitment close to mature trees is due to a Janzen-Connell effect. However, aggregates can continue to grow along colonization fronts. Second, long-distance dispersal events allow the formation of new clusters and play a crucial role in the colonization process. We investigate aggregate dynamics of Vouacapoua americana (Aublet) whose spatial pattern is not simply related to environmental conditions or to its seed dispersal. Regeneration does not occur in centers of aggregate of adults. We suggest that rare long-distance dispersal events and density-dependence predation of seeds and seedlings play a crucial role in formation of new clusters and structuration of larger aggregates. © 2013 International Association for Vegetation Science. |
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Université Claude Bernard Lyon 1, 43 Boulevard 11 Novembre 1918, Villeurbanne, 69100, France |
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11009233 (Issn) |
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Export Date: 10 March 2014; Source: Scopus; Coden: Jvese; Language of Original Document: English; Correspondence Address: Traissac, S.; AgroParisTech, UMR ECOlogie des Forêts de Guyane, Campus Agronomique, BP 709, Kourou, 97387, France; email: stephane.traissac@ecofog.gf |
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EcoFoG @ webmaster @ |
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532 |
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Sobotnik, J.; Sillam-Dusses, D.; Weyda, F.; Dejean, A.; Roisin, Y.; Hanus, R.; Bourguignon, T. |
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The frontal gland in workers of Neotropical soldierless termites |
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Journal Article |
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2010 |
Publication |
Naturwissenschaften |
Abbreviated Journal |
Naturwissenschaften |
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97 |
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5 |
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495-503 |
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Frontal gland; Workers; Soldierless termites; Apicotermitinae; Anoplotermes; Aparatermes |
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The presence of the frontal gland is well established in termite soldiers of Rhinotermitidae, Serritermitidae, and Termitidae. It is one of their main defensive adaptations or even an exclusive weapon. The gland was also occasionally reported in alate imagoes, but never in the worker caste. Here, we report the first observation of a frontal gland in workers of several Neotropical and one African species of Apicotermitinae. The ultrastructure of Aparatermes cingulatus and Anoplotermes nr. subterraneus is described in detail. In these two species, the gland is well-developed, functional and consists of class 1 secretory cells. The presence of envelope cells, wrapping the gland, is an unusual feature, as well as the presence of several zonulae adherens, connecting neighbouring glandular cells. The frontal gland of workers is homologous to this organ in soldiers and imagoes, as evidenced by the same position in the head and its connection to the same muscle. However, the defensive role of the frontal gland in workers remains to be confirmed. |
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[Sobotnik, Jan; Sillam-Dusses, David; Hanus, Robert] Acad Sci Czech Republic, Inst Organ Chem & Biochem, Res Team Infochem, CR-16610 Prague 6, Czech Republic, Email: robert@uochb.cas.cz |
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SPRINGER |
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0028-1042 |
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ISI:000277318800007 |
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EcoFoG @ webmaster @ |
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285 |
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Mony, R.; Dejean, A.; Bilong, C.F.B.; Kenne, M.; Rouland-Lefèvre, C. |
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Melissotarsus ants are likely able to digest plant polysaccharides |
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Journal Article |
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2013 |
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Comptes Rendus – Biologies |
Abbreviated Journal |
C. R. Biol. |
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336 |
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10 |
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500-504 |
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Ant-plant interactions; Degradation of plant material; Enzymatic activity; Melissotarsus ants |
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Melissotarsus ants have an extremely specialized set of behaviours. Both workers and gynes tunnel galleries in their host tree bark. Workers walk with their mesothoracic legs pointing upwards and tend Diaspididae hemiptera for their flesh. The ants use their forelegs to plug the galleries with silk that they secrete themselves. We hypothesised that the ants' energetic needs for nearly constant gallery digging could be satisfied through the absorption of host tree tissues; so, using basic techniques, we examined the digestive capacities of workers from two species. We show that workers are able to degrade oligosaccharides and heterosides as well as, to a lesser degree, polysaccharides. This is one of the rare reports on ants able to digest plant polysaccharides other than starch. © 2013 Académie des sciences. |
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IRD, UMR BIOEMCO-IBIOS, 32, rue Henri-Varagnat, 93143 Bondy cedex, France |
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16310691 (Issn) |
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Export Date: 6 December 2013; Source: Scopus; Coden: Crboc; doi: 10.1016/j.crvi.2013.08.003; Language of Original Document: English; Correspondence Address: Dejean, A.; Université de Toulouse, UPS, Ecolab, 118, route de Narbonne, 31062 Toulouse, France; email: alain.dejean@wanadoo.fr; References: Hölldobler, B., Wilson, E.O., (1990) The Ants, , Harvard University Press Cambridge, MA, USA 730 p; Duchesne, L.C., Larson, D.W., Cellulose and the evolution of plant life (1989) BioScience, 39, pp. 238-241; Watanabe, H., Tokuda, G., Cellulolytic Systems in Insects (2010) Annu. Rev. Entomol., 55, pp. 609-632; Wenzel, M., Schonig, I., Berchtold, M., Kampfer, P., König, K., Aerobic and facultatively anaerobic cellulolytic bacteria from the gut of the Termite Zootermopsis angusticollis (2002) J. Appl. Microbiol., 92, pp. 32-40; Brune, A., Microbial symbioses in the digestive tract of lower termites (2011) Beneficial Microorganisms in Multicellular Life Forms, pp. 3-25. , E. Rosenberg, U. Gophna, Heidelberg Springer; Tokuda, G., Watanabe, H., Hidden cellulases in termites: Revision of an old hypothesis (2007) Biol. Lett., 3, pp. 336-339; Nobre, T., Aanen, D.K., Fungiculture or termite husbandry? The ruminant hypothesis (2012) Insects, 3, pp. 307-323; Zientz, E., Feldhaar, H., Stoll, S., Gross, R., Insights into the microbial world associated with ants (2005) Arch. Microbiol., 184, pp. 199-206; Aylward, F., Burnum, K.E., Scott, J.J., Suen, G., Tringe, S.G., Metagenomic and metaproteomic insights into bacterial communities in leaf-cutter ant fungus gardens (2012) ISME J., pp. 1-14; Cook, S.C., Davidson, D.W., Nutritional and functional biology of exudate-feeding ants (2006) Entomol. Exp. Appl., 118, pp. 1-10; He, H., Chen, Y., Zhang, Y., Wei, C., Bacteria associated with gut lumen of Camponotus japonicus Mayr (2011) Environ. Entomol., 40, pp. 1405-1409; Blochmann, F., Über das Vorkommen von bakterienähnlichen Gebilden in den Geweben und Eiern verschiedener Insekten (1892) Zentbl. Bakteriol., 11, pp. 234-240; Feldhaar, H., Straka, J., Krischke, M., Berthold, K., Stoll, S., Nutritional upgrading for omnivorous carpenter ants by the endosymbiont Blochmannia (2007) BMC Biol., 5, p. 48; De Souza, D.J., Bézier, A., Depoix, D., Drezen, J.M., Lenoir, A., Blochmannia endosymbionts improve colony growth and immune defence in the ant Camponotus fellah (2009) BMC Microbiol., 9, p. 29; Van Borm, S., Buschinger, A., Boomsma, J.J., Billen, J., Tetraponera ants have gut symbionts related to nitrogen-fixing root-nodule bacteria (2002) Proc. R. Soc. Lond. B., 269, pp. 2023-2027; Eilmus, S., Heil, M., Bacterial associates of arboreal ants and their putative functions in an obligate ant-plant mutualism (2009) Appl. Env. Microbiol., 75, pp. 4324-4332; Russell, J.A., Moreau, C.S., Goldman-Huertas, B., Fujiwara, M., Lohman, D.J., Pierce, N.E., Bacterial gut symbionts are tightly linked with the evolution of herbivory in ants (2009) Proc. Natl. Acad. Sci. USA, 106, pp. 21236-21241; Delage-Darchen, B., Une fourmi de Côte d'Ivoire: Melissotarsus titubans Del., N. Sp. (1972) Insect. Soc., 19, pp. 213-226; Prins, A.J., Ben-Dov, Y., Rust, D.J., A new observation on the association between ants (Hymenoptera: Formicidae) and armoured scale insects (Homoptera: Diaspididae) (1975) J. Entomol. Soc. S. Afr., 38, pp. 211-216; Mony, R., Kenne, M., Dejean, A., (2002) Biology and Ecology of Pest Ants of the Genus Melissotarsus (Formicidae: Myrmicinae), with Special Reference to Tropical Fruit Tree Attacks, Sociobiology, 40, pp. 645-654; Mony, R., Fisher, B.L., Kenne, M., Tindo, M., Dejean, A., Behavioural ecology of bark-digging ants of the genus Melissotarsus (2007) Funct. Ecosyst. Commun., 1, pp. 121-128; Fisher, B.L., Robertson, H.G., Silk production by adult workers of the ant Melissotarsus emeryi (Hymenoptera, Formicidae) in South African fynbos (1999) Insect. Soc., 46, pp. 78-83; Sanson, G., The biomechanics of browsing and grazing (2006) Am. J. Bot., 93, pp. 1531-1545; Clissold, F., Sanson, G.D., Read, J., The paradoxical effects nutrient ratios and supply rates on an outbreaking insect herbivore, the Australian plague locust (2006) J. Anim. Ecol., 75, pp. 1000-1013; Cannon, C.A., (1998) Nutritional Ecology of the Carpenter Ant Camponotus Pennsylvanicus (De Geer): Macronutrient Preference and Particle Consumption, , (PhD thesis) Blacsburg VA; Eisner, T., A comparative morphological study of the proventriculus of ants (Hymenoptera, Formicidae) (1957) Bull. Mus. Comp. Zool., 116, pp. 441-490; Caetano, F.H., Can we use the digestive tract for phyllogenetic studies in ants (1990) Social Insects and the Environment, pp. 321-322. , G.K. Veeresh, B. Mallik, C.A. Viraktamath, Oxford & IBH publishing co. New Dehli; Delage, B., Recherches sur l'alimentation des fourmis granivores Messor capitatus Latr (1962) Insect. Soc., 9, pp. 137-143; Oettler, J., Johnson, R.A., The old ladies of the seed harvester ant Pogonomyrmex rugosus: Foraging performed by two groups of workers (2009) J. Insect. Behav., 22, pp. 217-226; Abbott, A., Nutrient dynamic of ants (1977) Production Ecology of Ants and Termites, pp. 233-244. , M.V. Brian, Cambridge University Press Cambridge; D'Ettorre, P., Mora, P., Dibangou, V., Rouland, C., Errard, C., The role of symbiotic fungus in the digestive metabolism of two species of fungus-growing ants (2002) J. Comp. Physiol. B, 172, pp. 169-176; Rouland, C., Lenoir, F., Lepage, M., The role of the symbiotic fungus in the digestive metabolism of several species of fungus-growing termites (1991) Comp. Biochem. Physiol., 99 A, pp. 657-663; Williams, J., Villaroya, H., Petek Galactosidase, F., II, III and IV from seeds of Trifolium repens (1978) Biochem. J., 175, pp. 1069-1077; Werner, W., Rey, H.G., Wielinger, R.H., Properties of a new chromogen for determination of glucose in blood according to the COD/POD method (1970) Anal. Chem., 252, pp. 224-228; Mora, P., Rouland, C., Comparison of hydrolytic enzyme produced during growth on carboidrate substrated by Termitomyces associates of Pseudacanthotermes spiniger and Microtermes subhyalinus (isopteran: Termitidae) (1994) Sociobiology, 26, pp. 39-53; Koning, R.E., Secondary Growth. Plant Physiology Information, , http://plantphys.info/plant_biology/secondary.shtml; Scheffrahn, R.H., Termites (Isoptera) (2008) Encyclopedia of Entomology Part 20, pp. 3737-3747. , J.L. Capinera, Springer Berlin; Richard, F.J., Mora, P., Errard, C., Rouland, C., Digestive capacities of leaf-cutting ants and the contribution of their cultivar to the degradation of plant material (2005) J. Comp. Physiol. B, 175, pp. 297-303; Ayre, G.L., The relationships between food and digestive enzymes in five species of ants (Hymenoptera: Formicidae) (1967) Can. Entomol., 99, pp. 408-411; Went, F.W., Wheeler, J., Wheeler, G.C., Feeding and digestion in some ants (Veromessor and Manica) (1972) BioScience, 22, pp. 82-88; Moller, I.E., De Fine Licht, H.H., Harholt, J., Willats, G.T., Boomsma, J.J., The dynamics of plant cell-wall polysaccharide decomposition in leaf-cutting ant fungus garden (2011) PloS ONE, 6, p. 17506 |
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EcoFoG @ webmaster @ |
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516 |
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Leroy, C.; Jauneau, A.; Quilichini, A.; Dejean, A.; Orivel, J. |
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Title |
Comparison between the anatomical and morphological structure of leaf blades and foliar domatia in the ant-plant Hirtella physophora (Chrysobalanaceae) |
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Journal Article |
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Year |
2008 |
Publication |
Annals of Botany |
Abbreviated Journal |
Ann. Bot. |
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Volume |
101 |
Issue |
4 |
Pages |
501-507 |
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Keywords |
anatomy; ant-plant mutualism; Chrysobalanaceae; extra-floral nectaries; French Guiana; Hirtella physophora; secondary domatia |
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Background and Aims Myrmecophytes, or ant-plants, are characterized by their ability to shelter colonies of some ant species in hollow structures, or ant-domatia, that are often formed by hypertrophy of the internal tissue at specific locations (i.e. trunk, branches, thorns and leaf pouches). In Hirtella physophora (Chrysobalanaceae), the focal species of this study, the ant-domatia consist of leaf pouches formed when the leaf rolls over onto itself to create two spheres at the base of the blade. Methods The morphological and anatomical changes through which foliar ant-domatia developed from the laminas are studied for the first time by using fresh and fixed mature leaves from the same H. physophora individuals. Key results Ant-domatia were characterized by larger extra-floral nectaries, longer stomatal apertures and lower stomatal density. The anatomical structure of the domatia differed in the parenchymatous tissue where palisade and spongy parenchyma were indistinct; chloroplast density was lower and lignified sclerenchymal fibres were more numerous compared with the lamina. In addition, the domatia were thicker than the lamina, largely because the parenchymatous and epidermal cells were enlarged. Conclusion Herein, the morphological and anatomical changes that permit foliar ant-domatia to be defined as a specialized leaf structure are highlighted. Similarities as well as structural modifications in the foliar ant-domatia compared with the lamina are discussed from botanical, functional and mutualistic points of view. These results are also important to understanding the reciprocal evolutionary changes in traits and, thus, the coevolutionary processes occurring in insect-plant mutualisms. |
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[Leroy, Celine; Quilichini, Angelique; Dejean, Alain; Orivel, Jerome] Univ Toulouse 3, CNRS, UMR 5174, Lab Evolut & Diversite Biol, F-31062 Toulouse 9, France, Email: orivel@cict.fr |
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OXFORD UNIV PRESS |
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0305-7364 |
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ISI:000253489700003 |
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EcoFoG @ eric.marcon @ |
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212 |
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Fichaux, M.; Béchade, B.; Donald, J.; Weyna, A.; Delabie, J.H.C.; Murienne, J.; Baraloto, C.; Orivel, J. |
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Title |
Habitats shape taxonomic and functional composition of Neotropical ant assemblages |
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Journal Article |
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2019 |
Publication |
Oecologia |
Abbreviated Journal |
Oecologia |
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Volume |
189 |
Issue |
2 |
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501-513 |
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Keywords |
Formicidae; Functional diversity; Habitat filtering; Rainforest; Traits; Formicidae |
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Abstract |
Determining assembly rules of co-occurring species persists as a fundamental goal in community ecology. At local scales, the relative importance of environmental filtering vs. competitive exclusion remains a subject of debate. In this study, we assessed the relative importance of habitat filtering and competition in structuring understory ant communities in tropical forests of French Guiana. Leaf-litter ants were collected using pitfall and Winkler traps across swamp, slope and plateau forests near Saül, French Guiana. We used a combination of univariate and multivariate analyses to evaluate trait response of ants to habitat characteristics. Null model analyses were used to investigate the effects of habitat filtering and competitive interactions on community assembly at the scale of assemblages and sampling points, respectively. Swamp forests presented a much lower taxonomic and functional richness compared to slope and plateau forests. Furthermore, marked differences in taxonomic and functional composition were observed between swamp forests and slope or plateau forests. We found weak evidence for competitive exclusion based on null models. Nevertheless, the contrasting trait composition observed between habitats revealed differences in the ecological attributes of the species in the different forest habitats. Our analyses suggest that competitive interactions may not play an important role in structuring leaf-litter ant assemblages locally. Rather, habitats are responsible for driving both taxonomic and functional composition of ant communities. |
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International Center for Tropical Botany, Department of Biological Sciences, Florida International University, Miami, FL 33199, United States |
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Springer Verlag |
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00298549 (Issn) |
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EcoFoG @ webmaster @ |
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863 |
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Fayad, I.; Baghdadi, N.; Guitet, S.; Bailly, J.-S.; Herault, B.; Gond, V.; El Hajj, M.; Tong Minh, D.H. |
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Aboveground biomass mapping in French Guiana by combining remote sensing, forest inventories and environmental data |
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Journal Article |
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2016 |
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International Journal of Applied Earth Observation and Geoinformation |
Abbreviated Journal |
International Journal of Applied Earth Observation and Geoinformation |
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52 |
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502-514 |
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Aboveground biomass mapping; Forests; French Guiana; ICESat GLAS; LiDAR |
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Mapping forest aboveground biomass (AGB) has become an important task, particularly for the reporting of carbon stocks and changes. AGB can be mapped using synthetic aperture radar data (SAR) or passive optical data. However, these data are insensitive to high AGB levels (>150 Mg/ha, and >300 Mg/ha for P-band), which are commonly found in tropical forests. Studies have mapped the rough variations in AGB by combining optical and environmental data at regional and global scales. Nevertheless, these maps cannot represent local variations in AGB in tropical forests. In this paper, we hypothesize that the problem of misrepresenting local variations in AGB and AGB estimation with good precision occurs because of both methodological limits (signal saturation or dilution bias) and a lack of adequate calibration data in this range of AGB values. We test this hypothesis by developing a calibrated regression model to predict variations in high AGB values (mean >300 Mg/ha) in French Guiana by a methodological approach for spatial extrapolation with data from the optical geoscience laser altimeter system (GLAS), forest inventories, radar, optics, and environmental variables for spatial inter- and extrapolation. Given their higher point count, GLAS data allow a wider coverage of AGB values. We find that the metrics from GLAS footprints are correlated with field AGB estimations (R2 = 0.54, RMSE = 48.3 Mg/ha) with no bias for high values. First, predictive models, including remote-sensing, environmental variables and spatial correlation functions, allow us to obtain “wall-to-wall” AGB maps over French Guiana with an RMSE for the in situ AGB estimates of ∼50 Mg/ha and R2 = 0.66 at a 1-km grid size. We conclude that a calibrated regression model based on GLAS with dependent environmental data can produce good AGB predictions even for high AGB values if the calibration data fit the AGB range. We also demonstrate that small temporal and spatial mismatches between field data and GLAS footprints are not a problem for regional and global calibrated regression models because field data aim to predict large and deep tendencies in AGB variations from environmental gradients and do not aim to represent high but stochastic and temporally limited variations from forest dynamics. Thus, we advocate including a greater variety of data, even if less precise and shifted, to better represent high AGB values in global models and to improve the fitting of these models for high values. © 2016 Elsevier B.V. |
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NOVELTIS, 153 rue du Lac, Labège, France |
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Export Date: 9 December 2016 |
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EcoFoG @ webmaster @ |
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699 |
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Ruelle, J.; Beauchene, J.; Thibaut, A.; Thibaut, B. |
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Comparison of physical and mechanical properties of tension and opposite wood from ten tropical rainforest trees from different species |
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2007 |
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Annals of Forest Science |
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Ann. For. Sci. |
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64 |
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5 |
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503-510 |
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tension wood; opposite wood; tropical rainforest; physical and mechanical properties |
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On 10 trees from 10 species of French Guyana tropical rainforest in a clear active process of restoring verticality growth strains were measured in situ in order to determine the occurrence of tension wood within samples. Wood specimens were cut in the vicinity of the growth strains measurements in order to measure some mechanical and physical properties. As suspected, tensile growth strains was very much higher in tension wood zone, because longitudinal modulus of elasticity was slightly higher. Longitudinal shrinkage was also much higher in tension wood than in opposite wood. |
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UMR EcoFoG, Kourou 97387, Guyana, Email: ruelle@nuagr1.agr.nagoya-u.ac.jp |
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EDP SCIENCES S A |
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1286-4560 |
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ISI:000248098600003 |
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EcoFoG @ eric.marcon @ |
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160 |
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Orivel, J.; Grangier, J.; Foucaud, J.; Le Breton, J.; Andres, F.X.; Jourdan, H.; Delabie, J.H.C.; Fournier, D.; Cerdan, P.; Facon, B.; Estoup, A.; Dejean, A. |
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Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges |
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2009 |
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Ecological Entomology |
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Ecol. Entomol. |
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34 |
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4 |
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504-512 |
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Biological invasion; disturbance; ecological traits; native; Wasmannia auropunctata |
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1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species' native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling-up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges. |
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[Orivel, Jerome; Grangier, Julien; Le Breton, Julien] Univ Toulouse 3, Lab Evolut & Divers Biol, CNRS, UMR 5174, F-31062 Toulouse 9, France, Email: orivel@cict.fr |
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WILEY-BLACKWELL PUBLISHING, INC |
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0307-6946 |
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ISI:000267659900010 |
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EcoFoG @ eric.marcon @ |
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202 |
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Yamamoto, H.; Almeras, T. |
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A mathematical verification of the reinforced-matrix hypothesis using the Mori-Tanaka theory |
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2007 |
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Journal of Wood Science |
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J. Wood Sci. |
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53 |
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6 |
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505-509 |
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Engineering |
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This article presents a theoretical verification of the reinforced-matrix hypothesis derived from tensor equations, σ W = σ f + σ m and ε W = ε f = ε m (Wood Sci Technol 32:171–182, 1998; Wood Sci Technol 33:311–325, 1999; J Biomech Eng 124:432–440, 2002), using classical Mori-Tanaka theory on the micromechanics of fiber-reinforced materials (Acta Metall 21:571–574, 1973; Micromechanics — dislcation and inclusions (in Japanese), pp 141–147, 1976). The Mori-Tanaka theory was applied to a small fragment of the cell wall undergoing changes in its physical state, such as those arising from sorption of moisture, maturation of wall components, or action of an external force, to obtain ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I. When the constitutive equation of each constituent material was applied to the equation ⟨σ A⟩D = ϕ·⟨σ F⟩I + (1−ϕ)·⟨σ M⟩D−I, the equations σ W = σ f + σ m and ε W = ε f = ε m were derived to lend support to the concept that two main phases, the reinforcing cellulose microfibril and the lignin-hemicellulose matrix, coexist in the same domain. The constitutive equations for the cell wall fragment were obtained without recourse to additional parameters such as Eshelby’s tensor S and Hill’s averaged concentration tensors AF and AM. In our previous articles, the coexistence of two main phases and σ W = σ f + σ m and ε W = ε f =ε m had been taken as our starting point to formulate the behavior of wood fiber with multilayered cell walls. The present article provides a rational explanation for both concepts. |
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Springer Japan |
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1435-0211 |
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EcoFoG @ eric.marcon @ |
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215 |
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