Rahali, H., & Stien, D. (2006). Highly-loaded amphiphilic polyimino resin: quench reagent and solid support for peptide synthesis. Tetrahedron Lett., 47(47), 8205–8207.
Abstract: We demonstrate herein that polyimino resin 4a prepared by condensation of alpha,alpha'-dichloro-p-xylene, ethylenediamine and tris-(2-aminoethyl)-amine can be successfully exploited as a quench reagent for acids and electrophiles both in aqueous and organic solutions. Scope and limitations of such a resin as a solid support for peptide synthesis were also investigated. (c) 2006 Elsevier Ltd. All rights reserved.
|
Dejean, A., Fisher, B. L., Corbara, B., Rarevohitra, R., Randrianaivo, R., Rajemison, B., et al. (2010). Spatial Distribution of Dominant Arboreal Ants in a Malagasy Coastal Rainforest: Gaps and Presence of an Invasive Species. PLoS One, 5(2), e9319.
Abstract: We conducted a survey along three belt transects located at increasing distances from the coast to determine whether a non-random arboreal ant assemblage, such as an ant mosaic, exists in the rainforest on the Masoala Peninsula, Madagascar. In most tropical rainforests, very populous colonies of territorially dominant arboreal ant species defend absolute territories distributed in a mosaic pattern. Among the 29 ant species recorded, only nine had colonies large enough to be considered potentially territorially dominant; the remaining species had smaller colonies and were considered non-dominant. Nevertheless, the null-model analyses used to examine the spatial structure of their assemblages did not reveal the existence of an ant mosaic. Inland, up to 44% of the trees were devoid of dominant arboreal ants, something not reported in other studies. While two Crematogaster species were not associated with one another, Brachymyrmex cordemoyi was positively associated with Technomyrmex albipes, which is considered an invasive species-a non-indigenous species that has an adverse ecological effect on the habitats it invades. The latter two species and Crematogaster ranavalonae were mutually exclusive. On the other hand, all of the trees in the coastal transect and at least 4 km of coast were occupied by T. albipes, and were interconnected by columns of workers. Technomyrmex albipes workers collected from different trees did not attack each other during confrontation tests, indicating that this species has formed a supercolony along the coast. Yet interspecific aggressiveness did occur between T. albipes and Crematogaster ranavalonae, a native species which is likely territorially dominant based on our intraspecific confrontation tests. These results suggest that the Masoala rainforest is threatened by a potential invasion by T. albipes, and that the penetration of this species further inland might be facilitated by the low density of native, territorially dominant arboreal ants normally able to limit its progression.
|
Baraloto, C., & Goldberg, D. E. (2004). Microhabitat associations and seedling bank dynamics in a neotropical forest. Oecologia, 141(4), 701–712.
Abstract: We conducted a rigorous test of tropical tree seedling microhabitat differentiation by examining microhabitat associations, survival and growth of established seedlings of ten tropical tree species representing a four-factor gradient in seed size. Eight microhabitat variables describing soil and light conditions were measured directly adjacent to each of 588 seedlings within twelve 10 x 100 m belt transects at Paracou, French Guiana, and at 264 reference points along the transects. From these measurements, we defined three principal components describing soil richness, soil softness and canopy openness. Six of ten species ( in 9 of 30 total cases) were distributed non-randomly with respect to microhabitat along at least one principal component. However, few species demonstrated clear microhabitat specialization. All shifts in distribution relative to reference points were in the same direction ( richer, softer soil). Furthermore, of 135 pairwise comparisons among the species, only 7 were significantly different. More than three-fourths of all seedlings (75.3%) survived over the 2-year monitoring period, but survival rates varied widely among species. In no case was the probability of survival influenced by any microhabitat parameter. Relative height growth rates for the seedlings over 2 years varied from – 0.031 cm cm(-1) year(-1) (Dicorynia guianensis, Caesalpiniaceae) to 0.088 cm cm(-1) year(-1) (Virola michelii, Myristicaceae). In only 4 of 30 cases was height growth significantly associated with one of the three principal components. Because the conditions in this study were designed to maximize the chance of finding microhabitat differentiation among a group of species differing greatly in life history traits, the lack of microhabitat specialization it uncovered suggests that microhabitat partitioning among tropical tree species at the established seedling stage is unlikely to contribute greatly to coexistence among these species.
Keywords: French Guiana; life history traits; light availability; regeneration niche; soil nutrients
|
Groc, S., Delabie, J. H. C., Fernández, F., Leponce, M., Orivel, J., Silvestre, R., et al. (2014). Leaf-litter ant communities (Hymenoptera: Formicidae) in a pristine Guianese rain-forest: Stable functional structure versus high species turnover. Myrmecological News, 19, 43–51.
Abstract: We compared the ant assemblages from four very heterogeneous habitats over a short-distance elevational gradient of vegetation (due to the presence of an inselberg) at the Nouragues Research Station, French Guiana. We focused on litter-dwelling ants, combining the use of pitfall traps and the Winkler method according to the Ants of the Leaf Litter Proto-col. This permitted us to note (1) a high leaf-litter ant diversity overall and a decreasing diversity gradient from the lowland rainforest to the top of the inselberg, and (2) differences in species density, composition and functional struc-ture. While the ant assemblages on the plateau and inselberg can be considered functionally similar and typical of an Amazonian rainforest, that of the transition forest, relatively homogenous, rather corresponded to an ant fauna typical of open areas. By contrast, the liana forest assemblage was unexpectedly richer and denser than the others, sheltering a litter-dwelling ant fauna dominated by numerous and abundant cryptic species. These taxonomical and functional dissi-milarities may reflect the influence of the environmental heterogeneity, which, through variable abiotic conditions, can contribute to maintaining a notably rich ant biodiversity in these Neotropical habitats.
Keywords: Diversity gradient; Functional groups; Habitat heterogeneity; Litter-dwelling ant communities; Local scale; Pristine Amazonian rainforest; Taxonomic and functional structure
|
Chartier, M., Pélozuelo, L., & Gibernau, M. (2011). Do floral odor profiles geographically vary with the degree of specificity for pollinators? Investigation in two sapromyophilous Arum species (Araceae). Ann. Soc. Entomol. Fr., 47(1-2), 71–77.
Abstract: We compared floral odour profiles among populations of two Arum species which show different degrees of specificity for their fly pollinators. Insects were collected from inflorescences in four populations of Arum italicum and two populations of Arum maculatum. In six Arum populations, we compared inflorescences odour profiles collected by Solid Phase Micro Extraction (SPME) and analysed by gas chromatography. We confirmed that from a pollination point of view, A. italicum is an opportunist species, as it is mainly pollinated by insects of the families Psychodidae, Chironomidae and Sciaridae, whereas A. maculatum is a specialist species, as it is 90% pollinated by Psychodidae. In all populations, Arum italicum was less attractive to pollinators than Arum maculatum. Floral odour profiles of A. italicum were not geographically structured among populations, suggesting a high gene flow or adaptation to a fluctuant guild of pollinators. On the contrary, odour profiles of A. maculatum varied between the two populations studied suggesting a lower gene flow or adaptation to different local pollinator preferences.
Keywords: Arum italicum; Arum maculatum; Floral scent; Psychodidae; Specificity
|
Bonal, D., Born, C., Brechet, C., Coste, S., Marcon, E., Roggy, J. C., et al. (2007). The successional status of tropical rainforest tree species is associated with differences in leaf carbon isotope discrimination and functional traits. Ann. For. Sci., 64(2), 169–176.
Abstract: We characterised the among species variability in leaf gas exchange and morphological traits under controlled conditions of seedlings of 22 tropical rainforest canopy species to understand the origin of the variability in leaf carbon isotope discrimination (Delta) among species with different growth and dynamic characteristics (successional gradient). Our results first suggest that these species pursue a consistent strategy in terms of. throughout their ontogeny (juveniles grown here versus canopy adult trees from the natural forest). Second, leaf Delta was negatively correlated with WUE and N, and positively correlated with g(s), but among species differences in Delta were mainly explained by differences in WUE. Finally, species belonging to different successional groups display distinct leaf functional and morphological traits. We confirmed that fast growing early successional species maximise carbon assimilation with high stomatal conductance. In contrast, fast and slow growing late successional species are both characterised by low carbon assimilation values, but by distinct stomatal conductance and leaf morphological features. Along the successional gradient, these differences result in much lower Delta for the intermediate species (i.e. fast growing late successional) as compared to the two other groups.
Keywords: C-13; functional diversity; leaf gas exchange; species grouping; tropical rainforest
|
Brouard, O., Le Jeune, A. H., Leroy, C., Cereghino, R., Roux, O., Pelozuelo, L., et al. (2011). Are Algae Relevant to the Detritus-Based Food Web in Tank-Bromeliads? PLoS One, 6(5), e20129.
Abstract: We assessed the occurrence of algae in five species of tank-bromeliads found in contrasting environmental sites in a Neotropical, primary rainforest around the Nouragues Research Station, French Guiana. The distributions of both algal abundance and biomass were examined based on physical parameters, the morphological characteristics of bromeliad species and with regard to the structure of other aquatic microbial communities held in the tanks. Algae were retrieved in all of the bromeliad species with mean densities ranging from similar to 10(2) to 10(4) cells/mL. Their biomass was positively correlated to light exposure and bacterial biomass. Algae represented a tiny component of the detrital food web in shaded bromeliads but accounted for up to 30 percent of the living microbial carbon in the tanks of Catopsis berteroniana, located in a highly exposed area. Thus, while nutrient supplies are believed to originate from wind-borne particles and trapped insects (i.e., allochtonous organic matter), our results indicate that primary producers (i.e., autochtonous organic matter) are present in this insectivorous bromeliad. Using a 24-h incubation of size-fractionated and manipulated samples from this plant, we evaluated the impact of mosquito foraging on algae, other microorganisms and rotifers. The prey assemblages were greatly altered by the predation of mosquito larvae. Grazing losses indicated that the dominant algal taxon, Bumilleriopsis sp., like protozoa and rotifers, is a significant part of the diet of mosquito larvae. We conclude that algae are a relevant functional community of the aquatic food web in C. berteroniana and might form the basis of a complementary non-detrital food web.
|
Bonal, D., Ponton, S., Le Thiec, D., Richard, B., Ningre, N., Herault, B., et al. (2011). Leaf functional response to increasing atmospheric CO(2) concentrations over the last century in two northern Amazonian tree species: a historical delta(13)C and delta(18)O approach using herbarium samples. Plant Cell Environ., 34(8), 1332–1344.
Abstract: We assessed the extent of recent environmental changes on leaf morphological (stomatal density, stomatal surface, leaf mass per unit area) and physiological traits (carbon isotope composition, delta(13)C(leaf), and discrimination, Delta(13)C(leaf), oxygen isotope composition, delta(18)O(leaf)) of two tropical rainforest species (Dicorynia guianensis; Humiria balsamifera) that are abundant in the Guiana shield (Northern Amazonia). Leaf samples were collected in different international herbariums to cover a 200 year time-period (1790-2004) and the whole Guiana shield. Using models describing carbon and oxygen isotope fractionations during photosynthesis, different scenarios of change in intercellular CO(2) concentrations inside the leaf (C(i)), stomatal conductance (g), and photosynthesis (A) were tested in order to understand leaf physiological response to increasing air CO(2) concentrations (C(a)). Our results confirmed that both species displayed physiological response to changing C(a). For both species, we observed a decrease of about 1.7% in delta(13)C(leaf) since 1950, without significant change in Delta(13)C(leaf) and leaf morphological traits. Furthermore, there was no clear change in delta(18)O(leaf) for Humiria over this period. Our simulation approach revealed that an increase in A, rather than a decrease in g, explained the observed trends for these tropical rainforest species, allowing them to maintain a constant ratio of C(i)/C(a).
Keywords: carbon isotope composition; environmental change; herbarium; oxygen isotope composition; photosynthesis; stomata; tropical rainforests
|
Fyllas, N. M., Patino, S., Baker, T. R., Nardoto, G. B., Martinelli, L. A., Quesada, C. A., et al. (2009). Basin-wide variations in foliar properties of Amazonian forest: phylogeny, soils and climate. Biogeosciences, 6(11), 2677–2708.
Abstract: We analysed 1040 individual trees, located in 62 plots across the Amazon Basin for leaf mass per unit area (M-A), foliar carbon isotopic composition (delta C-13) and leaf level concentrations of C, N, P, Ca, Mg, K and Al. All trees were identified to the species level with the dataset containing 58 families, 236 genera and 508 species, distributed across a wide range of soil types and precipitation regimes. Some foliar characteristics such as M-A, [C], [N] and [Mg] emerge as highly constrained by the taxonomic affiliation of tree species, but with others such as [P], [K], [Ca] and delta C-13 also strongly influenced by site growing conditions. By removing the environmental contribution to trait variation, we find that intrinsic values of most trait pairs coordinate, although different species ( characterised by different trait suites) are found at discrete locations along a common axis of coordination. Species that tend to occupy higher fertility soils are characterised by a lower M-A and have a higher intrinsic [N], [P], [K], [Mg] and delta C-13 than their lower fertility counterparts. Despite this consistency, different scaling patterns were observed between low and high fertility sites. Inter-relationships are thus substantially modified by growth environment. Analysing the environmental component of trait variation, we found soil fertility to be the most important predictor, influencing all leaf nutrient concentrations and delta C-13 and reducing M-A. Mean annual temperature was negatively associated with leaf level [N], [P] and [K] concentrations. Total annual precipitation positively influences M-A, [C] and delta C-13, but with a negative impact on [Mg]. These results provide a first basis for understanding the relationship between the physiological functioning and distribution of tree species across Amazonia.
|
Öpik, M., Zobel, M., Cantero, J. J., Davison, J., Facelli, J. M., Hiiesalu, I., et al. (2013). Global sampling of plant roots expands the described molecular diversity of arbuscular mycorrhizal fungi. Mycorrhiza, 23(5), 411–430.
Abstract: We aimed to enhance understanding of the molecular diversity of arbuscular mycorrhizal fungi (AMF) by building a new global dataset targeting previously unstudied geographical areas. In total, we sampled 96 plant species from 25 sites that encompassed all continents except Antarctica. AMF in plant roots were detected by sequencing the nuclear SSU rRNA gene fragment using either cloning followed by Sanger sequencing or 454-sequencing. A total of 204 AMF phylogroups (virtual taxa, VT) were recorded, increasing the described number of Glomeromycota VT from 308 to 341 globally. Novel VT were detected from 21 sites; three novel but nevertheless widespread VT (Glomus spp. MO-G52, MO-G53, MO-G57) were recorded from six continents. The largest increases in regional VT number were recorded in previously little-studied Oceania and in the boreal and polar climatic zones – this study providing the first molecular data from the latter. Ordination revealed differences in AM fungal communities between different continents and climatic zones, suggesting that both biogeographic history and environmental conditions underlie the global variation of those communities. Our results show that a considerable proportion of Glomeromycota diversity has been recorded in many regions, though further large increases in richness can be expected in remaining unstudied areas. © 2013 Springer-Verlag Berlin Heidelberg.
Keywords: 454-sequencing; Biogeography; Database; Diversity; Fungal macroecology; Glomeromycota
|
