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Revel, N., Alvarez, N., Gibernau, M., & Espíndola, A. (2012). Investigating the relationship between pollination strategies and the size-advantage model in zoophilous plants using the reproductive biology of Arum cylindraceum and other European Arum species as case studies. Arthropod-Plant Interact., 6(1), 35–44.
Abstract: The size-advantage model (SAM) explains the temporal variation of energetic investment on reproductive structures (i. e. male and female gametes and reproductive organs) in long-lived hermaphroditic plants and animals. It proposes that an increase in the resources available to an organism induces a higher relative investment on the most energetically costly sexual structures. In plants, pollination interactions are known to play an important role in the evolution of floral features. Because the SAM directly concerns flower characters, pollinators are expected to have a strong influence on the application of the model. This hypothesis, however, has never been tested. Here, we investigate whether the identity and diversity of pollinators can be used as a proxy to predict the application of the SAM in exclusive zoophilous plants. We present a new approach to unravel the dynamics of the model and test it on several widespread Arum (Araceae) species. By identifying the species composition, abundance and spatial variation of arthropods trapped in inflorescences, we show that some species (i. e. A. cylindraceum and A. italicum) display a generalist reproductive strategy, relying on the exploitation of a low number of dipterans, in contrast to the pattern seen in the specialist A. maculatum (pollinated specifically by two fly species only). Based on the model presented here, the application of the SAM is predicted for the first two and not expected in the latter species, those predictions being further confirmed by allometric measures. We here demonstrate that while an increase in the female zone occurs in larger inflorescences of generalist species, this does not happen in species demonstrating specific pollinators. This is the first time that this theory is both proposed and empirically tested in zoophilous plants. Its overall biological importance is discussed through its application in other non-Arum systems. © 2011 Springer Science+Business Media B.V.
Keywords: Araceae; Flower evolution; Plant-insect interactions; Reproductive strategy; Sex allocation
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Tahiri, A., Amissa Adima, A., Adjé, F. A., & Amusant, N. (2011). Pesticide effects and screening of extracts of Azadirachta Indica (A.) Juss. on the Macrotermes bellicosus rambur termite. Effet pesticide et screening des extraits de Azadirachta indica (A.) Juss. sur le termite Macroterme, 65(310), 79–88.
Abstract: To recommend applications in the field of a naturally insecticide plant substance as an alternative to chemical control against termite attacks, several important prerequisites need to be satisfied to ensure its effectiveness. The toxicity, lethal dose, mode of action, persistence of insecticide effect and chemical composition of total aqueous, alcohol and hexane extracts of the leaves and seeds of the neem tree, Azadirachta indica, were tested with the Macrotermes bellicosus termite. The extracts were found to be highly toxic to termites on contact, killing the entire population tested. The insecticide effect of the extracts persisted from 2.4 to 4.2 days. The aqueous and hexane extracts were the most toxic (LD50 0.422±0.018 to 4,466±0,162 mg/l). Contact and inhalation were both essential to their effectiveness. The aqueous extract of seeds, which is the most active, is also capable of being transferred through the colony during social tasks. However, it seems to have an anti-appetent effect on termites and does not act by ingestion. It contains phenol compounds (tannins and flavonoids) and saponins. The hexane extract of seeds is oily and contains 11 fatty acids as well as terpenoids, flavonoids and saponins.
Keywords: Azadirachta indica; Pesticide properties; Phytochemical screening; Termite
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Cachet, N., Ho-A-Kwie, F., Rivaud, M., Houel, E., Deharo, E., Bourdy, G., et al. (2012). Picrasin K, a new quassinoid from Quassia amara L. (Simaroubaceae). Phytochem. Lett., 5(1), 162–164.
Abstract: A new quassinoid Picrasin K 1 was isolated from a decoction made of Quassia amara leaves, traditionally used in French Guyana to treat malaria. The structure and relative stereochemistry of 1 was determined through extensive NMR analysis. Picrasin K showed a low activity against Plasmodium falciparum in vitro (IC 50 = 8 μM), and a similar low activity on human cancerous cells line (IC 50 = 7 μM on MCF-7 cells line). © 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
Keywords: Malaria; P. falciparum; Quassia amara; Quassinoids; Simaroubaceae
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Basset, C., Rodrigues, A. M. S., Eparvier, V., Silva, M. R. R., Lopes, N. P., Sabatier, D., et al. (2012). Secondary metabolites from Spirotropis longifolia (DC) Baill and their antifungal activity against human pathogenic fungi. Phytochemistry, 74, 166–172.
Abstract: A phytochemical study of the ethyl acetate extract of the roots and adventitious roots of Spirotropis longifolia, a monodominant tree species of the Guianan rainforest, has allowed the isolation of three compounds: 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethylpyrano-[5′, 6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin A), 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethyl-3′, 4′-dihydropyrano-[5′,6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin B), and 5,7-dihydroxy-6,8-diprenyl-2,2-dimethylpyrano[5,6: 3′,4′]-isoflavone (spirotropone). In addition, 10 known compounds, trans-oxyresveratrol, trans-resveratrol, piceatannol, daidzein, genistein, isoprunetin, lupeol, latifolol, gnetin D and gnetin E, were also isolated. These compounds were evaluated for their antifungal activity and their cytotoxicity, and their structures were established by 1D and 2D NMR, HRMS, CD and optical rotation measurements. © 2011 Elsevier Ltd. All rights reserved.
Keywords: Antifungal; Cytotoxic; Leguminosae; Monodominant species; Prenylated pterocarpans; Spirotropis longifolia
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Leroy, C., Corbara, B., Pélozuelo, L., Carrias, J. - F., Dejean, A., & Céréghino, R. (2012). Ant species identity mediates reproductive traits and allocation in an ant-garden bromeliad. Ann. Bot., 109(1), 145–152.
Abstract: •Background and Aims: Determining the sources of variation in floral morphology is crucial to understanding the mechanisms underlying Angiosperm evolution. The selection of floral and reproductive traits is influenced by the plants abiotic environment, florivores and pollinators. However, evidence that variations in floral traits result from mutualistic interactions with insects other than pollinators is lacking in the published literature and has rarely been investigated. We aimed to determine whether the association with either Camponotus femoratus or Pachycondyla goeldii (both involved in seed dispersal and plant protection) mediates the reproductive traits and allocation of Aechmea mertensii, an obligatory ant-garden tank-bromeliad, differently.•Methods: Floral and reproductive traits were compared between the two A. mertensii ant-gardens. The nitrogen flux from the ants to the bromeliads was investigated through experimental enrichments with stable isotopes (15N).•Key Results: Camponotus femoratus-associated bromeliads produced inflorescences up to four times longer than did P. goeldii-associated bromeliads. Also, the numbers of flowers and fruits were close to four times higher, and the number of seeds and their mass per fruit were close to 1·5 times higher in C. femoratus than in P. goeldii-associated bromeliads. Furthermore, the 15N-enrichment experiment showed that C. femoratus-associated bromeliads received more nitrogen from ants than did P. goeldii-associated bromeliads, with subsequent positive repercussions on floral development. Greater benefits were conferred to A. mertensii by the association with C. femoratus compared with P. goeldii ants.•Conclusions: We show for the first time that mutualistic associations with ants can result in an enhanced reproductive allocation for the bromeliad A. mertensii. Nevertheless, the strength and direction of the selection of floral and fruit traits change based on the ant species and were not related to light exposure. The different activities and ecological preferences of the ants may play a contrasting role in shaping plant evolution and speciation. © The Author 2011.
Keywords: δ15N; Aechmea mertensii; Bromeliaceae; bromeliad; Camponotus femoratus; floral traits; fruit-set; mutualistic ants; Pachycondyla goeldii; reproductive allocation; stable isotopes
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Malé, P. - J. G., Leroy, C., Dejean, A., Quilichini, A., & Orivel, J. (2012). An ant symbiont directly and indirectly limits its host plant's reproductive success. Evol. Ecol., 26(1), 55–63.
Abstract: In theory, mutualisms are intrinsically unstable, and the search for the maximum profit at the minimum cost should lead every mutualist to become a parasite. From an empirical point of view, mutualisms are ubiquitous and of major importance to ecosystems, suggesting the existence of mechanisms that enhance the maintenance of such relationships. We focused on the obligatory myrmecophytic association between the Neotropical plant Hirtella physophora (Chrysobalanaceae) and the ant Allomerus decemarticulatus (Myrmicinae). The plant shelters the ants in leaf pouches in exchange for protection from phytophagous insects. We experimentally demonstrated that the ants partially castrate their host plant by destroying almost two-thirds of its floral buds. The ants also impede pollination through their presence and interactions with pollinators. These results reveal that ant activity negatively affects the plant's reproduction both directly and indirectly. This dual negative effect does not result in the complete castration of the plant. We also highlight major limitations to plant reproduction due to the spontaneous abscission of flowers and to the limited quantity and/or poor quality of the pollen. These limitations must not be overlooked since they can alter the outcome of the association of H. physophora with its ant partner. We therefore conclude that the evolutionary fate of the relationship depends on both ant castration intensity and obstacles to plant fertilization not related to the presence of ants. © 2011 Springer Science+Business Media B.V.
Keywords: Cheater; Evolutionary conflict; Mutualism breakdown; Myrmecophyte; Pollination
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Paine, C. E. T., Norden, N., Chave, J., Forget, P. - M., Fortunel, C., Dexter, K. G., et al. (2012). Phylogenetic density dependence and environmental filtering predict seedling mortality in a tropical forest. Ecol. Lett., 15(1), 34–41.
Abstract: Negative density dependence (NDD) and environmental filtering (EF) shape community assembly, but their relative importance is poorly understood. Recent studies have shown that seedling's mortality risk is positively related to the phylogenetic relatedness of neighbours. However, natural enemies, whose depredations often cause NDD, respond to functional traits of hosts rather than phylogenetic relatedness per se. To understand the roles of NDD and EF in community assembly, we assessed the effects on seedling mortality of functional similarity, phylogenetic relatedness and stem density of neighbouring seedlings and adults in a species-rich tropical forest. Mortality risks increased for common species when their functional traits departed substantially from the neighbourhood mean, and for all species when surrounded by close relatives. This indicates that NDD affects community assembly more broadly than does EF, and leads to the tentative conclusion that natural enemies respond to phylogenetically correlated traits. Our results affirm the prominence of NDD in structuring species-rich communities. © 2011 Blackwell Publishing Ltd/CNRS.
Keywords: Community assembly; Density dependence; French Guiana; Generalised linear mixed models; Janzen-Connell hypothesis; Seedling recruitment; Species coexistence; Survival
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Dejean, A., Cereghino, R., Carpenter, J. M., Corbara, B., Herault, B., Rossi, V., et al. (2011). Climate change impact on neotropical social wasps. PLoS ONE, 6(11), e27004.
Abstract: Establishing a direct link between climate change and fluctuations in animal populations through long-term monitoring is difficult given the paucity of baseline data. We hypothesized that social wasps are sensitive to climatic variations, and thus studied the impact of ENSO events on social wasp populations in French Guiana. We noted that during the 2000 La Niña year there was a 77.1% decrease in their nest abundance along ca. 5 km of forest edges, and that 70.5% of the species were no longer present. Two simultaneous 13-year surveys (1997-2009) confirmed the decrease in social wasps during La Niña years (2000 and 2006), while an increase occurred during the 2009 El Niño year. A 30-year weather survey showed that these phenomena corresponded to particularly high levels of rainfall, and that temperature, humidity and global solar radiation were correlated with rainfall. Using the Self-Organizing Map algorithm, we show that heavy rainfall during an entire rainy season has a negative impact on social wasps. Strong contrasts in rainfall between the dry season and the short rainy season exacerbate this effect. Social wasp populations never recovered to their pre-2000 levels. This is probably because these conditions occurred over four years; heavy rainfall during the major rainy seasons during four other years also had a detrimental effect. On the contrary, low levels of rainfall during the major rainy season in 2009 spurred an increase in social wasp populations. We conclude that recent climatic changes have likely resulted in fewer social wasp colonies because they have lowered the wasps' resistance to parasitoids and pathogens. These results imply that Neotropical social wasps can be regarded as bio-indicators because they highlight the impact of climatic changes not yet perceptible in plants and other animals. © 2011 Dejean et al.
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Rodrigues, A. M., Amusant, N., Beauchene, J., Eparvier, V., Lemenager, N., Baudasse, C., et al. (2011). The termiticidal activity of Sextonia rubra (Mez) van der Werff (Lauraceae) extract and its active constituent rubrynolide. Pest Manage. Sci., 67(11), 1420–1423.
Abstract: Termites are degradation agents that inflict severe damage on wood. Some long-lasting Amazonian trees can resist these insects by producing toxic secondary metabolites. These metabolites could potentially replace synthetic termiticidal products which are becoming more restricted to use. Results: Sextonia rubra is resistant to termite-induced degradation. It has been demonstrated that this species naturally produces an ethyl-acetate-soluble termiticidal metabolite, rubrynolide, to protect its wood. Assays in the presence of tropical and invasive termites established that both rubrynolide and crude ethyl acetate extract from S. rubra wood can be used as a treatment for the protection of sensitive woods against termites. Conclusion: Rubrynolide and S. rubra extract are promising candidates for the replacement of synthetic termiticides. © 2011 Society of Chemical Industry.
Keywords: Nasutitermes macrocephalus; Reticulitermes flavipes; Rubrynolide; Sextonia rubra extract; Wood preservation
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Zhang, T., Bai, S. - L., Bardet, S., Almeras, T., Thibaut, B., & Beauchene, J. (2011). Radial variations of vibrational properties of three tropical woods. J. Wood Sci., 57(5), 377–386.
Abstract: The radial trends of vibrational properties, represented by the specific dynamic modulus (E′/ρ) and damping coefficient (tan δ), were investigated for three tropical rainforest hardwood species (Simarouba amara, Carapa procera, and Symphonia globulifera) using free-free flexural vibration tests. The microfibril angle (MFA) was estimated using X-ray diffraction. Consistent patterns of radial variations were observed for all studied properties. E′/ρ was found to decrease from pith to bark, which was strongly related to the increasing pith-bark trend of MFA. The variation of tan δ along the radius could be partly explained by MFA and partly by the gradient of extractives due to heartwood formation. The coupling effect of MFA and extractives could be separated through analysis of the log(tan δ) versus log(E′/ρ) diagram. For the species studied, the extractive content putatively associated with heartwood formation generally tends to decrease the wood damping coefficient. However, this weakening effect of extractives was not observed for the inner part of the heartwood, suggesting that the mechanical action of extractives was reduced during their chemical ageing. © 2011 The Japan Wood Research Society.
Keywords: Damping coefficient; Dynamic modulus; Extractives; Microfibril angle; Tropical woods
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