Binelli, G., Montaigne, W., Sabatier, D., Scotti-Saintagne, C., & Scotti, I. (2020). Discrepancies between genetic and ecological divergence patterns suggest a complex biogeographic history in a Neotropical genus. Ecology and Evolution, 10(11), 4726–4738.
Abstract: Phylogenetic patterns and the underlying speciation processes can be deduced from morphological, functional, and ecological patterns of species similarity and divergence. In some cases, though, species retain multiple similarities and remain almost indistinguishable; in other cases, evolutionary convergence can make such patterns misleading; very often in such cases, the “true” picture only emerges from carefully built molecular phylogenies, which may come with major surprises. In addition, closely related species may experience gene flow after divergence, thus potentially blurring species delimitation. By means of advanced inferential methods, we studied molecular divergence between species of the Virola genus (Myristicaceae): widespread Virola michelii and recently described, endemic V. kwatae, using widespread V. surinamensis as a more distantly related outgroup with different ecology and morphology—although with overlapping range. Contrary to expectations, we found that the latter, and not V. michelii, was sister to V. kwatae. Therefore, V. kwatae probably diverged from V. surinamensis through a recent morphological and ecological shift, which brought it close to distantly related V. michelii. Through the modeling of the divergence process, we inferred that gene flow between V. surinamensis and V. kwatae stopped soon after their divergence and resumed later, in a classical secondary contact event which did not erase their ecological and morphological differences. While we cannot exclude that initial divergence occurred in allopatry, current species distribution and the absence of geographical barriers make complete isolation during speciation unlikely. We tentatively conclude that (a) it is possible that divergence occurred in allopatry/parapatry and (b) secondary contact did not suppress divergence. © 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
Keywords: allopatric divergence; Amazon; Guiana Shield; interspecific gene flow; Myristicaceae; secondary contact; Virola
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Courtois, E. A., Dexter, K. G., Paine, C. E. T., Stien, D., Engel, J., Baraloto, C., et al. (2016). Evolutionary patterns of volatile terpene emissions across 202 tropical tree species. Ecol Evol, 6(9), 2854–2864.
Abstract: Plant responses to natural enemies include formation of secondary metabolites acting as direct or indirect defenses. Volatile terpenes represent one of the most diverse groups of secondary metabolites. We aimed to explore evolutionary patterns of volatile terpene emission. We measured the composition of damage-induced volatile terpenes from 202 Amazonian tree species, spanning the angiosperm phylogeny. Volatile terpenes were extracted with solid-phase micro extraction and desorbed in a gas chromatography–mass spectrometry for compound identification. The chemical diversity of the terpene blend showed a strong phylogenetic signal as closely related species emitted a similar number of compounds. Closely related species also tended to have compositionally similar blends, although this relationship was weak. Meanwhile, the ability to emit a given compound showed no significant phylogenetic signal for 200 of 286 compounds, indicating a high rate of diversification in terpene synthesis and/or great variability in their expression. Three lineages (Magnoliales, Laurales, and Sapindales) showed exceptionally high rates of terpene diversification. Of the 70 compounds found in >10% of their species, 69 displayed significant correlated evolution with at least one other compound. These results provide insights into the complex evolutionary history of volatile terpenes in angiosperms, while highlighting the need for further research into this important class of compounds.
Keywords: Chemical defense; French Guiana; herbivory; secondary metabolites; tropical forest
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Denis, T., Richard-Hansen, C., Brunaux, O., Etienne, M. - P., Guitet, S., & Herault, B. (2017). Biological traits, rather than environment, shape detection curves of large vertebrates in neotropical rainforests. Ecol Appl, 27(5), 1564–1577.
Abstract: Line transect surveys are widely used in Neotropical rainforests to estimate the population abundance of medium- and large-sized vertebrates. The use of indices such as encounter rate has been criticized because the probability of animal detection may fluctuate due to the heterogeneity of environmental conditions among sites. In addition, the morphological and behavioral characteristics (biological traits) of species affect their detectability. In this study, we compared the extent to which environmental conditions and species’ biological traits bias abundance estimates in terra firme rainforests in French Guiana. The selected environmental conditions included both physical conditions and forest structure covariates, while the selected biological traits included the morphological and behavioral characteristics of species. We used the distance sampling method to model the detection probability as an explicit function of environmental conditions and biological traits and implemented a model selection process to determine the relative importance of each group of covariates. Biological traits contributed to the variability of animal detectability more than environmental conditions, which had only a marginal effect. Detectability was best for large animals with uniform or disruptive markings that live in groups in the canopy top. Detectability was worst for small, solitary, terrestrial animals with mottled markings. In the terra firme rainforests that represent ~80% of the Amazonia and Guianas regions, our findings support the use of relative indices such as the encounter rate to compare population abundance between sites in species-specific studies. Even though terra firme rainforests may appear similar between regions of Amazonia and the Guianas, comparability must be ensured, especially in forests disturbed by human activity. The detection probability can be used as an indicator of species’ vulnerability to hunting and, thus, to the risk of local extinction. Only a few biological trait covariates are required to correctly estimate the detectability of the majority of medium- and large-sized vertebrates. Thus, a biological trait model could be useful in predicting the detection probabilities of rare, uncommon, or localized species for which few data are available to fit the detection function.
Keywords: abundance; camouflage; distance sampling; encounter rate; French Guiana; hunting vulnerability; line transect; Neotropical terra firme rainforests; relative abundance
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Duplais, C., & Estevez, Y. (2017). Tandem Biocatalysis Unlocks the Challenging de Novo Production of Plant Natural Products. ChemBioChem, 18(22), 2192–2195.
Abstract: Intimate partnership: Knowledge of the biocatalytic cascades in different cellular compartments is limited, but deciphering these systems in nature can be used to inspire synthetic strategies. Two studies report new insights into the biosynthesis of alkaloids and sesterterpenoids in plants. This highlight presents these novel biotransformations to illustrate how tandem biocatalysis can impact the future of natural product production.
Keywords: alkaloids; biosynthesis; enzyme catalysis; protein engineering; terpenes
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Valverde-Barrantes, O. J., Authier, L., Schimann, H., & Baraloto, C. (2021). Root anatomy helps to reconcile observed root trait syndromes in tropical tree species. American Journal of Botany, 108(5), 744–755.
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Mahoui, S., Moulay, M. S., & Omrane, A. (2020). Finite element approach to linear parabolic pointwise control problems of incomplete data. International Journal of Systems Science, 51(14), 2597–2609.
Abstract: In this paper we give a priori error estimates for finite element approximations of linear parabolicproblems with pointwise control and incomplete data. We discretise the optimal control problemby using piecewise linear and continuous finite elements for the space discretisation of the state,and we use the backward Euler scheme for time discretisation. We prove a priori error estimates forthe state, the adjoint-state as well as for the low-regret pointwise optimal control.
Keywords: Optimal control problem ; low-regret control ; pointwise control ; finite element method ; a priori error estimates
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Paine, C. E. T., Stahl, C., Courtois, E. A., Patino, S., Sarmiento, C., & Baraloto, C. (2010). Functional explanations for variation in bark thickness in tropical rain forest trees. Funct. Ecol., 24(6), 1202–1210.
Abstract: P>1. The complex structure of tree bark reflects its many functions, which include structural support as well as defence against fire, pests and pathogens. Thick bark, however, might limit respiration by the living tissues of the trunk. Nevertheless, little research has addressed community-level variation in bark thickness, and to the best of our knowledge, no one has tested multiple hypotheses to explain variation in bark thickness. 2. We conducted an extensive survey of bark thickness within and among species of trees in the tropical rain forests of French Guiana. Trunk bark thickness increased by 1 center dot 2 mm per 10 cm increase in stem diameter, and varied widely at all taxonomic levels. Mean trunk bark thickness was 4 center dot 5 mm (range: 0 center dot 5-29 mm), which was less that found in two Amazonian rain forests in previous studies. This survey of bark thickness should be of use for forest management since tree survival through fire is strongly predicted by bark thickness. 3. We combined the survey data with multiple datasets to test several functional hypotheses proposed to explain variation in bark thickness. We found bark to provide an average of 10% of the flexural rigidity of tree stems, which was substantially less than that found in the only other study of bark stiffness. Bark thickness was uncorrelated with species' association with fire-prone habitats, suggesting that the influence of fire on bark thickness does not extend into moist Forests. There was also little evidence that bark thickness is affected by its function as a defence against herbivory. Nor was there evidence that thick bark limits trunk respiration. 4. A re-analysis of previously collected anatomical data indicated that variation in rhytidome (non-conducting outer bark) thickness explains much of the variation in overall bark thickness. As rhytidome is primarily involved in protecting the living tissues of the trunk, we suggest that bark thickness is driven mostly by its defensive function. 5. Functional explanations for the variation in bark thickness were not clear-cut. Nevertheless, this study provides a foundation for further investigation of the functional bases of bark in tropical trees.
Keywords: bark thickness; fire ecology; flexural rigidity; herbivore defence; periderm; rhytidome; trunk respiration
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Wagner, F., Rutishauser, E., Blanc, L., & Herault, B. (2010). Effects of Plot Size and Census Interval on Descriptors of Forest Structure and Dynamics. Biotropica, 42(6), 664–671.
Abstract: This study was designed to explicitly formulate the effect of census interval and plot size on the variability of descriptors of tropical forest structure (stand density, basal area, aboveground biomass [AGB]) and dynamic (tree growth, mortality and recruitment rates, biomass fluxes). A unique dataset from a broad plot network (37.5 ha) surveyed every 2 yr over a 16-yr period was used to develop and parameterize a new statistical model predicting the coefficients of variation for each forest descriptor. More than 90 percent of the inherent variability of these coefficients was predicted using a simple model including plot size and census interval in a Bayesian modeling framework. All descriptors of forest structure varied by <10 percent for plot sizes 42 ha. Among the descriptors of forest dynamics, AGB loss was the most variable. The number of 6.25 ha plots required to estimate its mean, over a 16-yr period, within a 20 percent error of the mean remains above four. This contrasts with a relative constant flux of biomass entering the plot through tree growth and tree recruitment. Tree growth was remarkably well estimated with <15 percent variability for a 2-yr census in a plot of 2 ha. This study provides an easy method to assess dataset limitations in efforts to estimate descriptors of forest structure and dynamic, which is of primary importance to decipher any clear consequences of global change in tropical forests.
Keywords: Amazonia; biomass fluxes; coefficient of variation; forest permanent plots; turnover rates; WinBUGS
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Orivel, J., Corbara, B., & Dejean, A. (2010). Constraints and adaptation in the arboreal life of ants. Biofutur, 315, 34–37.
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Leroy, C., Cereghino, R., Camas, J. F., Pelozuelo, L., Dejean, A., & Corbara, B. (2010). Several aspects of the life of vascular epiphytes. Biofutur, 315, 38–41.
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