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Talaga, S., Petitclerc, F., Carrias, J. - F., Dezerald, O., Leroy, C., Céréghino, R., et al. (2017). Environmental drivers of community diversity in a neotropical urban landscape: a multi-scale analysis. Landscape Ecology, 32(9), 1805–1818.
Abstract: Context: Many aquatic communities are linked by the aerial dispersal of multiple, interacting species and are thus structured by processes occurring in both the aquatic and terrestrial compartments of the ecosystem. Objectives: To evaluate the environmental factors shaping the aquatic macroinvertebrate communities associated with tank bromeliads in an urban landscape. Methods: Thirty-two bromeliads were georeferenced to assess the spatial distribution of the aquatic meta-habitat in one city. The relative influence of the aquatic and terrestrial habitats on the structure of macroinvertebrate communities was analyzed at four spatial scales (radius = 10, 30, 50, and 70 m) using redundancy analyses. Results: We sorted 18,352 aquatic macroinvertebrates into 29 taxa. Water volume and the amount of organic matter explained a significant part of the taxa variance, regardless of spatial scale. The remaining variance was explained by the meta-habitat size (i.e., the water volume for all of the bromeliads within a given surface area), the distance to the nearest building at small scales, and the surface area of buildings plus ground cover at larger scales. At small scales, the meta-habitat size influenced the two most frequent mosquito species in opposite ways, suggesting spatial competition and coexistence. Greater vegetation cover favored the presence of a top predator. Conclusions: The size of the meta-habitat and urban landscape characteristics influence the structure of aquatic communities in tank bromeliads, including mosquito larval abundance. Modifications to this landscape will affect both the terrestrial and aquatic compartments of the urban ecosystem, offering prospects for mosquito management during urban planning. © 2017, Springer Science+Business Media B.V.
Keywords: Aquatic metacommunity; Landscape ecology; Mosquitoes; Neotropics; Scale dependency; Tank bromeliads; Urban ecology
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Scotti, I., Montaigne, W., Cseke, K., & Traissac, S. (2013). RaBoT: A rarefaction-by-bootstrap method to compare genome-wide levels of genetic diversity. Ann. Forest Sci., 70(6), 631–635.
Abstract: Context: No efficient method is available to compare multi-locus estimates of diversity while taking into account inter-locus and inter-population stochastic variance. The advent of genome scan approaches makes the development of such tests absolutely necessary. Aims: We developed a method to compare genome-wide diversity estimates while taking into account – and factoring out – variation in census size and making use of inter-locus variance to assess significance of differences in diversity levels. Methods: An approach based on rarefaction with bootstrap re-sampling (RaBoT) was implemented into a test of multi-locus comparison of diversity coded in R. The properties of the test were studied by applying it to simulated populations with varying diversity levels and varying differences in diversity levels. The test was then applied to empirical data from disturbed and undisturbed populations of Virola michelii (Myristicaceae) genotyped at 693 amplified fragment length polymorphism (AFLP) markers. Results: RaBoT was found to be rather conservative, with large numbers of false negatives when the diversity in the compared populations was similar, and false positives mostly associated to comparisons of populations with extremely high levels of diversity. When applied to empirical data, RaBoT detected higher genetic diversity in a post-disturbance than in an undisturbed population and lower genetic diversity in a seedling than in the corresponding adult population, but it also revealed differences in diversity between subgroups within the disturbed and undisturbed plots. Conclusion: RaBoT is a sensitive method to compare multi-locus levels of diversity that can be applied both at the genotype level for dominant markers (e.g. AFLP) and at the allele level for biallelic codominant markers (e.g. single-nucleotide polymorphisms). © 2013 INRA and Springer-Verlag France.
Keywords: Diversity comparison; Genome scan; Genome-level diversity; Population genetics; Statistical testing
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Clair, B., Alteyrac, J., Gronvold, A., Espejo, J., Chanson, B., & Alméras, T. (2013). Patterns of longitudinal and tangential maturation stresses in Eucalyptus nitens plantation trees. Ann. Forest Sci., 70(8), 801–811.
Abstract: Context: Tree orientation is controlled by asymmetric mechanical stresses set during wood maturation. The magnitude of maturation stress differs between longitudinal and tangential directions, and between normal and tension woods. Aims: We aimed at evaluating patterns of maturation stress on eucalypt plantation trees and their relation with growth, with a focus on tangential stress evaluation. Methods: Released maturation strains along longitudinal and tangential directions were measured around the circumference of 29 Eucalyptus nitens trees, including both straight and leaning trees. Results: Most trees produced asymmetric patterns of longitudinal maturation strain, but more than half of the maturation strain variability occurred between trees. Many trees produced high longitudinal tensile stress all around their circumference. High longitudinal tensile stress was not systematically associated with the presence of gelatinous layer. The average magnitude of released longitudinal maturation strain was found negatively correlated to the growth rate. A methodology is proposed to ensure reliable evaluation of released maturation strain in both longitudinal and tangential directions. Tangential strain evaluated with this method was lower than previously reported. Conclusion: The stress was always tensile along the longitudinal direction and compressive along the tangential direction, and their respective magnitude was positively correlated. This correlation does not result from a Poisson effect but may be related to the mechanism of maturation stress generation. © 2013 # The Author(s) 2013. This article is published with open access at Springerlink.com.
Keywords: Eucalyptus nitens; G-layer; Longitudinal maturation stress; Maturation strain; Tangential maturation stress; Tension wood
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Delnatte, C., & Meyer, J. - Y. (2012). Plant introduction, naturalization, and invasion in French Guiana (South America). Biol. Invasions, 14(5), 915–927.
Abstract: Continental tropical ecosystems are generally viewed as less vulnerable to biological invasions than island ones. Their apparent resistance to invasive alien species is often attributed to their higher native biota diversity and complexity. However, with the increase of human activities and disturbances and the accelerate rate of introductions of plant species, these apparently resilient continental ecosystems are now experiencing alien plant naturalization and invasion events. In order to illustrate this emergent phenomenon, we compiled a list of all known introduced and naturalized plant species in French Guiana (Guiana Shield, South America). A total of 490 alien plants were recorded, about 34% of which are currently naturalized, mainly species belonging to the Acanthaceae and Fabaceae (Faboideae) in the Eudicotyledons, and Poaceae (grasses) and Arecaceae (palms) in the Monocotyledons. The coastal dry and wet savannas appears to be vulnerable to plant invasion (with 165 naturalized species, about 34% of the alien flora), especially by Acacia mangium (Mimosaceae) and Melaleuca quinquenervia (Myrtaceae) which are forming localized but dense monotypic stands. Both tree species, intentionnally introduced for reforestation, rehabilitation, and as garden ornamentals and have the potential to spread with increasing human disturbances The number and abundance of naturalized alien plants in the relatively undisturbed tropical lowland rainforests and savannas remains still very low. Therefore, surveillance, early detection, and eradication of potential plant invaders are crucial; moreover collaboration with neighbouring countries of the Guiana Shield is essential to prevent the introduction of potentially invasive species which are still not present in French Guiana. © 2011 Springer Science+Business Media B.V.
Keywords: Acacia mangium; French Guiana; Invasive plant; Melaleuca quinquenervia; Naturalization; Savanna
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Fukami, T., Nakajima, M., Fortunel, C., Fine, P. V. A., Baraloto, C., Russo, S. E., et al. (2017). Geographical variation in community divergence: insights from tropical forest monodominance by ectomycorrhizal trees. American Naturalist, 190, S105–S122.
Abstract: Convergence occurs in both species traits and community structure, but how convergence at the two scales influences each other remains unclear. To address this question, we focus on tropical forest monodominance, in which a single, often ectomycorrhizal (EM) tree species occasionally dominates forest stands within a landscape otherwise characterized by diverse communities of arbuscular mycorrhizal (AM) trees. Such monodominance is a striking potential example of community divergence resulting in alternative stable states. However, it is observed only in some tropical regions. A diverse suite of AM and EM trees locally codominate forest stands elsewhere. We develop a hypothesis to explain this geographical difference using a simulation model of plant community assembly. Simulation results suggest that in a region with a few EM species (e.g., South America), EM trees experience strong selection for convergent traits that match the abiotic conditions of the environment. Consequently, EM species successfully compete against other species to form monodominant stands via positive plant-soil feedbacks. By contrast, in a region with many EM species (e.g., Southeast Asia), species maintain divergent traits because of complex plant-soil feedbacks, with no species having traits that enablemonodominance. An analysis of plant trait data from Borneo and Peruvian Amazon was inconclusive. Overall, this work highlights the utility of geographical comparison in understanding the relationship between trait convergence and community convergence. © 2017 by The University of Chicago.
Keywords: Community assembly; Mycorrhizae; Plant traits; Plant-soil feedback; Priority effects; Species pools
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Faustin, M., Maciuk, A., Salvin, P., Roos, C., & Lebrini, M. (2015). Corrosion inhibition of C38 steel by alkaloids extract of Geissospermum laeve in 1M hydrochloric acid: Electrochemical and phytochemical studies. Corrosion Science, 92, 287–300.
Abstract: Corrosion inhibition by alkaloids extract (AE) from Geissospermum laeve on C38 steel in 1. M HCl is investigated with electrochemical studies. Inhibition efficiency of 92% is reached with 100. mg/L of AE at 25. °C. Potentiodynamic polarization showed that the extract behaves as mixed-type inhibitors. The Nyquist plots showed that increasing AE concentration, charge-transfer resistance increased and double-layer capacitance decreased, involving increased inhibition efficiency. Adsorption of the inhibitor molecules corresponds to Langmuir adsorption isotherm. Immersion time and temperature effects were investigated using EIS and potentiodynamic polarization. SEM and EDX supported the adsorption conclusions. The active compound responsible for the corrosion inhibition is geissospermine.
Keywords: A. C38 steel; B. Eis; B. Sem; C. Acid corrosion; C. Anodic protection; C. Cathodic protection
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Lebrini, M., Robert, F., & Roos, C. (2011). Alkaloids Extract from Palicourea guianensis Plant as Corrosion Inhibitor for C38 Steel in 1 M Hydrochloric Acid Medium. Int. J. Electrochem. Sci., 6(3), 847–859.
Abstract: Corrosion inhibition effect of alkaloids extract from Palicourea guianensis plant (AEPG) on C38 tell in 1 M HCl medium has been investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The polarization studies that AEPG acts as mixed-type inhibitor. The electrochemical impedance spectroscopy showed that the charge transfer resistance increases and the double layer capacitance decreases on increasing plant extract concentration. The inhibition efficiency of the extract obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of the extract. Inhibition efficiency of 89% was achieved with 100 mg L-1 of AEPG at 25 degrees C. The obtained results showed that, the Palicourea guianensis extract could serve as an effective inhibitor for the corrosion of steel in acid media. The adsorption of AEPG obeys the Langmuir adsorption isotherm.
Keywords: Palicourea guianensis; corrosion inhibitors; C38 steel; acidic media; adsorption
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Duval, R., & Duplais, C. (2017). Fluorescent natural products as probes and tracers in biology. Natural Product Reports, 34(2), 161–193.
Abstract: Covering: 1985 up to the end of 2016 Fluorescence is a remarkable property of many natural products in addition to their medicinal and biological values. Herein, we provide a review on these peculiar secondary metabolites to stimulate prospecting of them as original fluorescent tracers, endowed with unique photophysical properties and with applications in most fields of biology. The compounds are spectrally categorized (i.e. fluorescing from violet to the near infra-red) and further structurally classified within each category. Natural products selected for their high impact in modern fluorescence-based biological studies are highlighted throughout the article. Finally, we discuss aspects of chemical ecology where fluorescent natural products might have key evolutionary roles and thus open new research directions in the field. © 2017 The Royal Society of Chemistry.
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Lormée, H., Berzins, R., Rocheteau, V., De Coster, F., Denis, T., & Richard-Hanssen, C. (2021). Seasonal Variation in the Home Ranges of Black Curassow, Crax alector, in French Guiana. Tropical Conservation Science, 14(1), 1–10.
Abstract: Cracidae is the most threatened avian family in the Neotropics, mainly because of habitat destruction, heavy hunting pressure and poaching. In French Guiana, Black Curassows are heavily hunted, although basic knowledge of the ecological and demographical traits of the species remains limited. Such a gap prevents any attempt to assess the impact of hunting and to help stakeholders to develop proposals ensuring hunting sustainability. The spatial relationship between animals and their habitat is important for conservation management, being related to population densities through complex patterns. Here, we report on a radio-tracking study of Black Curassows in tropical primary rainforest, in Nouragues National Reserve, French Guiana. The aims of the study were to estimate home range size and its variation across seasons, and to quantify movement patterns of the birds. We captured and fitted VHF tags to four adults, and tracked them for 10 to 21.5 months. Daily movements were recorded, and home ranges estimated using the Kernel Density method, for two consecutive wet seasons and one dry season. Using 95% and 50% Kernel densities, the average annual home range and core area were 96.3± 32.6 ha (SE) and 22.8 ± 2.8 ha respectively. Home ranges appeared spatially stable over the two years, and overlapped between neighbouring groups. During the dry season, Black Curassows did not migrate but tended to enlarge their home range, with greater daily movements and higher home range overlap. Although additional data are still needed, our results can help to improve the knowledge and management of this poorly studied species
Keywords: spatial ecology, Cracids, tracking, Kernel method, Home range, movement pattern
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Henkel, T. W., Wilson, A. W., Aime, M. C., Dierks, J., Uehling, J. K., Roy, M., et al. (2014). Cantharellaceae of Guyana II: New species of Craterellus, new South American distribution records for Cantharellus guyanensis and Craterellus excelsus, and a key to the Neotropical taxa. Mycologia, 106(2), 307–324.
Abstract: Craterellus olivaceoluteus sp. nov. and Craterellus cinereofimbriatus sp. nov. are described as new to science. These fungi were collected from Guyana in association with ectomycorrhizal host trees in the genera Dicymbe (Fabaceae subfam. Caesalpinioideae) and Pakaraimaea (Dipterocarpaceae). Cantharellus guyanensis Mont., originally described from French Guiana, is redescribed from recent collections from Guyana, with additional range extensions for the species provided based on material examined from French Guiana, Venezuela, and north central, northeastern and southern Brazil, circumscribing nearly the entire Guiana Shield region and beyond. A new distribution record from French Guiana is provided for Craterellus excelsus T.W. Henkel & Aime. Macromorphological, micromorphological and habitat data are provided for the new species and C. guyanensis as well as DNA sequence data from the nuclear ribosomal regions of the internal transcribed spacer (ITS) and 28S large subunit (LSU); additional sequence data is provided for C. guyanensis and C. excelsus specimens collected outside Guyana. The relationships of these taxa within the Cantharellaceae were evaluated with phylogenetic analyses of ITS and LSU sequence data. This work brings the total number of Cantharellaceae species known from Guyana to eight. A key to the Cantharellus and Craterellus species known from the lowland Neotropics and extralimital montane Central and South America is provided. © 2014 by The Mycological Society of America.
Keywords: Cantharellales; Coccoloba; Dicymbe; Ectomycorrhizae; Guiana shield; Tropical fungi
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