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Barassé, V., Touchard, A., Téné, N., Tindo, M., Kenne, M., Klopp, C., et al. (2019). The peptide venom composition of the fierce stinging ant tetraponera aethiops (formicidae: Pseudomyrmecinae). Toxins, 11(12), 732.
Abstract: In the mutualisms involving certain pseudomyrmicine ants and different myrmecophytes (i.e., plants sheltering colonies of specialized “plant-ant” species in hollow structures), the ant venom contributes to the host plant biotic defenses by inducing the rapid paralysis of defoliating insects and causing intense pain to browsing mammals. Using integrated transcriptomic and proteomic approaches, we identified the venom peptidome of the plant-ant Tetraponera aethiops (Pseudomyrmecinae). The transcriptomic analysis of its venom glands revealed that 40% of the expressed contigs encoded only seven peptide precursors related to the ant venom peptides from the A-superfamily. Among the 12 peptide masses detected by liquid chromatography-mass spectrometry (LC-MS), nine mature peptide sequences were characterized and confirmed through proteomic analysis. These venom peptides, called pseudomyrmecitoxins (PSDTX), share amino acid sequence identities with myrmeciitoxins known for their dual offensive and defensive functions on both insects and mammals. Furthermore, we demonstrated through reduction/alkylation of the crude venom that four PSDTXs were homo- and heterodimeric. Thus, we provide the first insights into the defensive venom composition of the ant genus Tetraponera indicative of a streamlined peptidome.
Keywords: Defensive venom; Dimeric peptides; Peptidome; Tetraponera aethiops
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Solander, K. C., Newman, B. D., Carioca De Araujo, A., Barnard, H. R., Berry, Z. C., Bonal, D., et al. (2020). The pantropical response of soil moisture to El Niño. Hydrol. Earth Syst. Sci., 24(5), 2303–2322.
Abstract: The 2015–2016 El Niño event ranks as one of the most severe on record in terms of the magnitude and extent of sea surface temperature (SST) anomalies generated in the tropical Pacific Ocean. Corresponding global impacts on the climate were expected to rival, or even surpass, those of the 1997–1998 severe El Niño event, which had SST anomalies that were similar in size. However, the 2015–2016 event failed to meet expectations for hydrologic change in many areas, including those expected to receive well above normal precipitation. To better understand how climate anomalies during an El Niño event impact soil moisture, we investigate changes in soil moisture in the humid tropics (between ±25∘) during the three most recent super El Niño events of 1982–1983, 1997–1998 and 2015–2016, using data from the Global Land Data Assimilation System (GLDAS). First, we use in situ soil moisture observations obtained from 16 sites across five continents to validate and bias-correct estimates from GLDAS (r2=0.54). Next, we apply a k-means cluster analysis to the soil moisture estimates during the El Niño mature phase, resulting in four groups of clustered data. The strongest and most consistent decreases in soil moisture occur in the Amazon basin and maritime southeastern Asia, while the most consistent increases occur over eastern Africa. In addition, we compare changes in soil moisture to both precipitation and evapotranspiration, which showed a lack of agreement in the direction of change between these variables and soil moisture most prominently in the southern Amazon basin, the Sahel and mainland southeastern Asia. Our results can be used to improve estimates of spatiotemporal differences in El Niño impacts on soil moisture in tropical hydrology and ecosystem models at multiple scales.
Keywords: Cluster analysis; Oceanography; Soil moisture; Surface waters; Tropics; Climate anomalies; Clustered datum; Hydrologic changes; Land data assimilation systems; Sea surface temperature anomalies; Situ soil moistures; Tropical hydrologies; Tropical Pacific ocean; Soil surveys
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Moore, A. L., McCarthy, M. A., Parris, K. M., & Moore, J. L. (2014). The optimal number of surveys when detectability varies. PLoS ONE, 9(12), e115345.
Abstract: The survey of plant and animal populations is central to undertaking field ecology. However, detection is imperfect, so the absence of a species cannot be determined with certainty. Methods developed to account for imperfect detectability during surveys do not yet account for stochastic variation in detectability over time or space. When each survey entails a fixed cost that is not spent searching (e.g., time required to travel to the site), stochastic detection rates result in a trade-off between the number of surveys and the length of each survey when surveying a single site. We present a model that addresses this trade-off and use it to determine the number of surveys that: 1) maximizes the expected probability of detection over the entire survey period; and 2) is most likely to achieve a minimally-acceptable probability of detection. We illustrate the applicability of our approach using three practical examples (minimum survey effort protocols, number of frog surveys per season, and number of quadrats per site to detect a plant species) and test our model's predictions using data from experimental plant surveys. We find that when maximizing the expected probability of detection, the optimal survey design is most sensitive to the coefficient of variation in the rate of detection and the ratio of the search budget to the travel cost. When maximizing the likelihood of achieving a particular probability of detection, the optimal survey design is most sensitive to the required probability of detection, the expected number of detections if the budget were spent only on searching, and the expected number of detections that are missed due to travel costs. We find that accounting for stochasticity in detection rates is likely to be particularly important for designing surveys when detection rates are low. Our model provides a framework to do this. © 2014 Moore et al.
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Fisher, J. B., Malhi, Y., Bonal, D., Da Rocha, H. R., De Araujo, A. C., Gamo, M., et al. (2009). The land-atmosphere water flux in the tropics. Glob. Change Biol., 15(11), 2694–2714.
Abstract: Tropical vegetation is a major source of global land surface evapotranspiration, and can thus play a major role in global hydrological cycles and global atmospheric circulation. Accurate prediction of tropical evapotranspiration is critical to our understanding of these processes under changing climate. We examined the controls on evapotranspiration in tropical vegetation at 21 pan-tropical eddy covariance sites, conducted a comprehensive and systematic evaluation of 13 evapotranspiration models at these sites, and assessed the ability to scale up model estimates of evapotranspiration for the test region of Amazonia. Net radiation was the strongest determinant of evapotranspiration (mean evaporative fraction was 0.72) and explained 87% of the variance in monthly evapotranspiration across the sites. Vapor pressure deficit was the strongest residual predictor (14%), followed by normalized difference vegetation index (9%), precipitation (6%) and wind speed (4%). The radiation-based evapotranspiration models performed best overall for three reasons: (1) the vegetation was largely decoupled from atmospheric turbulent transfer (calculated from X decoupling factor), especially at the wetter sites; (2) the resistance-based models were hindered by difficulty in consistently characterizing canopy (and stomatal) resistance in the highly diverse vegetation; (3) the temperature-based models inadequately captured the variability in tropical evapotranspiration. We evaluated the potential to predict regional evapotranspiration for one test region: Amazonia. We estimated an Amazonia-wide evapotranspiration of 1370 mm yr(-1), but this value is dependent on assumptions about energy balance closure for the tropical eddy covariance sites; a lower value (1096 mm yr(-1)) is considered in discussion on the use of flux data to validate and interpolate models.
Keywords: Amazon; eddy covariance; evaporation; evapotranspiration; ISLSCP-II; LBA; model; remote sensing; tropical
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Maia, A. C. D., Dötterl, S., Kaiser, R., Silberbauer-Gottsberger, I., Teichert, H., Gibernau, M., et al. (2012). The Key Role of 4-methyl-5-vinylthiazole in the Attraction of Scarab Beetle Pollinators: A Unique Olfactory Floral Signal Shared by Annonaceae and Araceae. J. Chem. Ecol., 38(9), 1072–1080.
Abstract: Cyclocephaline scarabs are specialised scent-driven pollinators, implicated with the reproductive success of several Neotropical plant taxa. Night-blooming flowers pollinated by these beetles are thermogenic and release intense fragrances synchronized to pollinator activity. However, data on floral scent composition within such mutualistic interactions are scarce, and the identity of behaviorally active compounds involved is largely unknown. We performed GC-MS analyses of floral scents of four species of Annona (magnoliids, Annonaceae) and Caladium bicolor (monocots, Araceae), and demonstrated the chemical basis for the attraction of their effective pollinators. 4-Methyl-5-vinylthiazole, a nitrogen and sulphur-containing heterocyclic compound previously unreported in flowers, was found as a prominent constituent in all studied species. Field biotests confirmed that it is highly attractive to both male and female beetles of three species of the genus Cyclocephala, pollinators of the studied plant taxa. The origin of 4-methyl-5-vinylthiazole in plants might be associated with the metabolism of thiamine (vitamin B1), and we hypothesize that the presence of this compound in unrelated lineages of angiosperms is either linked to selective expression of a plesiomorphic biosynthetic pathway or to parallel evolution. © 2012 Springer Science+Business Media, LLC.
Keywords: Beetle pollination; Floral scent; Gas chromatography-mass spectrometry (GC-MS); Olfactory-mediated attraction
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Mariano, C. S. F., Silva Santos, I. D. A., Groc, S., Leroy, C., Malé, P. - J., Ruiz-González, M. X., et al. (2011). The karyotypes of Gigantiops destructor (Fabricius) and other ants from French Guiana (Formicidae). Ann. Soc. Entomol. Fr., 47(1-2), 140–146.
Abstract: The aim of this study, which was conducted in French Guiana, was to characterize the karyotypes of nine ant species belonging to the genera Anochetus, Apterostigma, Cyphomyrmex, Camponotus, Gigantiops, Myrmicocrypta, Odontomachus and Pseudomyrmex, and to compare them with published data. We present the first descriptions of the karyotypes of Gigantiops destructor (Fabricius), an endemic Formicinae of the Amazonian region, which is the only living species in the tribe Gigantiopini, and of a species from the poorly-known cryptic genus Myrmicocrypta, which belongs to the Myrmicinae tribe Attini.
Keywords: Chromosome number; Diversity; Minimum interaction theory
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Fouquet, A., Ledoux, J. - B., Dubut, V., Noonan, B. P., & Scotti, I. (2012). The interplay of dispersal limitation, rivers, and historical events shapes the genetic structure of an Amazonian frog. Biol. J. Linn. Soc., 106(2), 356–373.
Abstract: Disentangling the impact of landscape features such as rivers and historical events on dispersal is a challenging but necessary task to gain a comprehensive picture of the evolution of diverse biota such as that found in Amazonia. Adenomera andreae, a small, territorial, terrestrial frog species of the Amazonian forest represents a good model for such studies. We combined cytochromeb sequences with 12 microsatellites to investigate the genetic structure at two contrasted spatial scales in French Guiana: along a ∼6-km transect, to evaluate dispersal ability, and between paired bank populations along a ∼65-km stretch of the Approuague river, to test the effect of rivers as barriers to dispersal. We observed significant spatial genetic structure between individuals at a remarkably small geographical scale, and conclude that the species has a restricted dispersal ability that is probably tied to its life-history traits. Mitochondrial and microsatellite data also indicate a high level of differentiation among populations on opposite banks of the river, and, in some cases, among populations on the same riverbank. These results suggest that the observed population structure in A.andreae is the result of restricted dispersal abilities combined with the action of rivers and Quaternary population isolation. Given that Amazonia hosts a great portion of anurans, as well as other small vertebrates, that display life-history traits comparable with A.andreae, we argue that our analyses provide new insights into the complex interactions among evolutionary processes shaping Amazonian biodiversity. © 2012 The Linnean Society of London.
Keywords: Amazonia; Amphibian; Gene flow; Microsatellites; Mitochondrial DNA; Spatial genetic structure
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Leroy, C., Petitclerc, F., Orivel, J., Corbara, B., Carrias, J. - F., Dejean, A., et al. (2017). The influence of light, substrate and seed origin on the germination and establishment of an ant-garden bromeliad. Plant Biol J, 19(1), 70–78.
Abstract: Plant germination and development depend upon a seed's successful dispersal into a suitable habitat and its ability to grow and survive within the surrounding biotic and abiotic environment. The seeds of Aechmea mertensii, a tank-bromeliad species, are dispersed by either Camponotus femoratus or Neoponera goeldii, two ant species that initiate ant gardens (AGs). These two mutualistic ant species influence the vegetative and reproductive traits of the bromeliad through their divergent ecological preferences (i.e. light and substrate). We hypothesised that the seeds dispersed by these two ant species have underlying genetic differences affecting germination, growth and survival of A. mertensii seedlings in different ways. To test this, we used an experimental approach consisting of sowing seeds of A. mertensii: (i) taken from the two AG–ant associations (i.e. seed origin), (ii) in two contrasting light conditions, and (iii) on three different substrates. Light and substrate had significant effects on germination, survival and on eight key leaf traits reflecting plant performance. Seed origin had a significant effect only on germination and on two leaf traits (total dry mass and relative growth rate). Overall, this bromeliad performs better (i.e. high growth and survival rates) when growing both in the shade and in the carton nest developed by C. femoratus ants. These results suggest that the plasticity of the tank bromeliad A. mertensii is mainly due to environment but also to genetic differences related to seed origin, as some traits are heritable. Thus, these two ant species may play contrasting roles in shaping plant evolution and speciation.
Keywords: Aechmea mertensii; bromeliad; French Guiana; germination; plant performance; survival
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Freycon, V., Krencker, M., Schwartz, D., Nasi, R., & Bonal, D. (2010). The impact of climate changes during the Holocene on vegetation in northern French Guiana. Quat. Res., 73(2), 220–225.
Abstract: The impact of climatic changes that occurred during the last glacial maximum and the Holocene on vegetation changes in the Amazon Basin and the Guiana Shield are still widely debated. The aim of our study was to investigate whether major changes in vegetation (i.e. transitions between rainforests and C-4 savannas) occurred in northern French Guiana during the Holocene. We measured variations in the delta C-13 of soil organic matter at eight sites now occupied by forest or savannah. The forest sites were selected to cover two regions (forest refugia and peneplains) which are thought to have experienced different intensities of disturbance during the latest Pleistocene and the Holocene. We found that none of the forest sites underwent major disturbances during the Holocene, i.e. they were not replaced by C-4 savannahs or C-4 forest savannahs for long periods. Our results thus suggest that tropical rainforests in northern French Guiana were resilient to drier climatic conditions during the Holocene. Nevertheless, geographical and vertical variations in the C-13 of SOM were compatible with minor changes in vegetation, variations in soil processes or in soil physical properties. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved.
Keywords: Holocene; Vegetation change; French Guiana; Carbon isotope composition; Soil organic matter
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Heuertz, M., Caron, H., Scotti-Saintagne, C., Pétronelli, P., Engel, J., Tysklind, N., et al. (2020). The hyperdominant tropical tree Eschweilera coriacea (Lecythidaceae) shows higher genetic heterogeneity than sympatric Eschweilera species in French Guiana. Plant Ecol. Evol., 153(1), 67–81.
Abstract: Background and aims – The evolutionary history of Amazonia’s hyperabundant tropical tree species, also known as “hyperdominant” species, remains poorly investigated. We assessed whether the hyperdominant Eschweilera coriacea (DC.) S.A.Mori (Lecythidaceae) represents a single genetically cohesive species, and how its genetic constitution relates to other species from the same clade with which it occurs sympatrically in French Guiana. Methods – We sampled 152 individuals in nine forest sites in French Guiana, representing 11 species of the genus Eschweilera all belonging to the Parvifolia clade, with emphasis on E. coriacea. Samples were genotyped at four simple sequence repeat (SSR) markers. We delimited gene pools, i.e., genetically coherent putative taxa, using STRUCTURE software and principal component analysis. We compared the genetic assignment of individuals with their morphological species determination and estimated genetic diversity and differentiation for gene pools and species. We also estimated genome size using flow cytometry. Key results – SSR profiles commonly displayed up to four alleles per genotype, suggesting that the investigated Eschweilera species bear a paleopolyploid signature. Flow cytometry suggested that the studied species are diploid with haploid genome sizes of 871–1046 Mbp. We detected five gene pools and observed a good correspondence between morphological and genetic delimitation for Eschweilera sagotiana Miers and the undescribed morphospecies E. sp. 3 (which resembles E. grandiflora (Aubl.) Sandwith), and to a lesser extent for E. decolorans Sandwith and E. micrantha (O.Berg) Miers. Eschweilera coriacea was the most genetically diverse species and included individuals assigned to each gene pool. Conclusions – We found no conclusive evidence for cryptic species within E. coriacea in French Guiana. SSRs detected fewer gene pools than expected based on morphology in the Parvifolia clade but discriminated evolutionary relationships better than available plastid markers. A positive trend between demographic abundance of species and allelic richness illustrates that hyperdominants may have a high evolutionary potential. This hypothesis can be tested using more powerful genomic data in combination with tree phenotypic trait variation and characterization of niche breadth, to enhance our understanding of the causes of hyperdominance in Amazonian trees.
Keywords: Cryptic species; Eschweilera; Hyperdominant tropical trees; Microsatellites; Species complex; Species delimitation
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