Abstract: 1. Our understanding of the contribution of interspecific interactions to functional diversity in nature lags behind our knowledge of spatial and temporal patterns. Although two-species mutualisms are found in all types of ecosystems, the study of their ecological influences on other community members has mostly been limited to third species, while their influence on entire communities remains largely unexplored. 2. We hypothesized that mutualistic interactions between two respective ant species and an epiphyte mediate the biological traits composition of entire invertebrate communities that use the same host plant, thereby affecting food webs and functional diversity at the community level. 3. Aechmea mertensii (Bromeliaceae) is both a phytotelm ('plant-held water') and an ant-garden epiphyte. We sampled 111 bromeliads (111 aquatic invertebrate communities) associated with either the ant Pachycondyla goeldii or Camponotus femoratus. The relationships between ants, bromeliads and invertebrate abundance data were examined using a redundancy analysis. Biological traits information for invertebrates was structured using a fuzzy-coding technique, and a co-inertia analysis between traits and abundance data was used to interpret functional differences in bromeliad ecosystems. 4. The vegetative traits of A. mertensii depended on seed dispersion by C. femoratus and P. goeldii along a gradient of local conditions. The ant partner selected sets of invertebrates with traits that were best adapted to the bromeliads' morphology, and so the composition of the biological traits of invertebrate phytotelm communities depends on the identity of the ant partner. Biological traits suggest a bottom-up control of community structure in C. femoratus-associated phytotelmata and a greater structuring role for predatory invertebrates in P. goeldii-associated plants. 5. This study presents new information showing that two-species mutualisms affect the functional diversity of a much wider range of organisms. Most biological systems form complex networks where nodes (e. g. species) are more or less closely linked to each other, either directly or indirectly, through intermediate nodes. Our observations provide community-level information about biological interactions and functional diversity, and perspectives for further observations intended to examine whether large-scale changes in interacting species/community structure over broad geographical and anthropogenic gradients affect ecosystem functions.

Abstract: The mechanism for tree orientation in angiosperms is based on the production of high tensile stress on the upper side of the inclined axis. In many species, the stress level is strongly related to the presence of a peculiar layer, called the G-layer, in the fibre cell wall. The structure of the G-layer has recently been described as a hydrogel thanks to N-2 adsorption-desorption isotherms of supercritically dried samples showing a high mesoporosity (pores size from 2-50 nm). This led us to revisit the concept of the G-layer that had been, until now, only described from anatomical observation. Adsorption isotherms of both normal wood and tension wood have been measured on six tropical species. Measurements show that mesoporosity is high in tension wood with a typical thick G-layer while it is much less with a thinner G-layer, sometimes no more than normal wood. The mesoporosity of tension wood species without a G-layer is as low as in normal wood. Not depending on the amount of pores, the pore size distribution is always centred around 6-12 nm. These results suggest that, among species producing fibres with a G-layer, large structural differences of the G-layer exist between species.

Abstract: Mechanical signals have an impact on plant development. Tropical rainforest trees display large variability for life-history traits related to biomechanics and therefore are a unique study system to better understand biomechanical trait variability from an evolutionary perspective. From sequences and gene expression data available in model species, we developed specific primers for six candidate genes for mechano-sensing in five tropical species. Most of the gene sequences were polymorphic in most species.

Abstract: A comparative study of two Sn-based composite materials as negative electrode for Li-ion accumulators is presented. The former SnB0.6P0.4O2.9 obtained by in-situ dispersion of SnO in an oxide matrix is shown to be an amorphous tin composite oxide (ATCO). The latter Sn-0.72[BPO4](0.28) obtained by ex-situ dispersion of Sri in a borophosphate matrix consists of Sri particles embedded in a crystalline BPO4 matrix. The electrochemical responses of ATCO and Sn-0.72.[BPO4](0.28) composite in galvanostatic mode show reversible capacities of about 450 and 530 mAhg(-1), respectively, with different irreversible capacities (60% and 29%). Analysis of these composite materials by Sn-119 Mossbauer spectroscopy in transmission (TMS) and emission (CEMS) modes confirms that ATCO is an amorphous Sn-II composite oxide and shows that in the case of Sn-0.72[BPO4](0.28), the Surface of the tin clusters is mainly formed by Sn-II in an amorphous interface whereas the bulk of the clusters is mainly formed by Sn-0. The determination of the recoilless free fractions f (Lamb-Mossbauer factors) leads to the effective fraction of both Sn-0 and Sn-II species in such composites. The influence of chemical composition and especially of the surface-to-bulk tin species ratio oil the electrochemical behaviour has been analysed for several Sn-x[BPO4](1-x) composite materials (0.17 < x < 0.91). The cell using the compound Sn-0.72[BPO4](0.28) as active material exhibits interesting electrochemical performances (reversible capacity of 500 mAh g(-1) at C/5 rate). (C) 2009 Elsevier Inc. All rights reserved.

Abstract: The maintenance in the long run of a positive carbon balance under very low irradiance is a prerequisite for survival of tree seedlings below the canopy or in small gaps in a tropical rainforest. To provide a quantitative basis for this assumption, experiments were carried out to determine whether construction cost (CC) and payback time for leaves and support structures, as well as leaf life span (i) differ among species and (ii) display an irradiance-elicited plasticity. Experiments were also conducted to determine whether leaf life span correlates to CC and payback time and is close to the optimal longevity derived from an optimization model. Saplings from 13 tropical tree species were grown under three levels of irradiance. Specific-CC was computed, as well as CC scaled to leaf area at the metamer level. Photosynthesis was recorded over the leaf life span. Payback time was derived from CC and a simple photosynthesis model. Specific-CC displayed only little interspecific variability and irradiance-elicited plasticity, in contrast to CC scaled to leaf area. Leaf life span ranged from 4 months to > 26 months among species, and was longest in seedlings grown under lowest irradiance. It was always much longer than payback time, even under the lowest irradiance. Leaves were shed when their photosynthesis had reached very low values, in contrast to what was predicted by an optimality model. The species ranking for the different traits was stable across irradiance treatments. The two pioneer species always displayed the smallest CC, leaf life span, and payback time. All species displayed a similar large irradiance-elicited plasticity.