Dejean, A., Carpenter, J. M., Gibernau, M., Leponce, M., & Corbara, B. (2010). Nest relocation and high mortality rate in a Neotropical social wasp: Impact of an exceptionally rainy La Nina year. C. R. Biol., 333(1), 35–40.
Abstract: After noting the forecast of a La Nina episode, associated with heavy rainfall in French Guiana, we monitored the fate of wasp nests before and during the 2006 short rainy season. The population of the most abundant epiponine wasp species, Polybia bistriata, decreased dramatically during the short rainy season (60.6% of the nests disappeared) then remained low for at least 18 months. Colonies that survived moved from the shelter of large, low leaves (a situation well adapted to the previous dry season) of the most frequent substrate tree, Clusia grandiflora (Clusiaceae), to upper leaves, better ventilated and whose orientation provides good protection from the rain. Therefore, the possibility of moving the nest higher during the first rains following the dry season seems very adaptive as colonies that do not do so are eliminated during the La Nina years, whose frequency will increase with global climate change. (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Vespidae; Population size variation; Microevolution; La Nina; French Guiana
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Delabie, J. H. C., Cereghino, R., Groc, S., Dejean, A., Gibernau, M., Corbara, B., et al. (2009). Ants as biological indicators of Wayana Amerindian land use in French Guiana. C. R. Biol., 332(7), 673–684.
Abstract: We examined the ecological impact of traditional land use by Wayana Amerindians in French Guiana using ants as bio-indicators. Ants were sampled through a rapid assessment method and the core results analyzed using Kohonen's self-organizing maps (SOM). Our sample sites included: (1) a Wayana village; (2) a cassava plantation; (3) an abandoned cassava plantation; (4) a forest fragment near the village; (5) a riparian forest; and (6) a primary terra firma forest. The ant diversity decreases according to the decree to which the habitat is disturbed. The SOM allowed us to compare the ecological succession between the six habitats. The protocol used is robust since the same conclusions were drawn using partial data. To cite this article: J.H.C Delabie et al., C R. Biologies 332 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Landscape ecology; Traditional land use; Formicidae; Rapid assessment; Pit-fall traps; Self-Organizing Maps
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Corbara, B., Carpenter, J. M., Cereghino, R., Leponce, M., Gibernau, M., & Dejean, A. (2009). Diversity and nest site selection of social wasps along Guianese forest edges: assessing the influence of arboreal ants. C. R. Biol., 332(5), 470–479.
Abstract: monitored), and estimate that we recorded up to 73% of the local social wasp fauna. This baseline study was complemented by a long-term survey of the same area and the examination of isolated trees (permitting us to record two additional species, resulting in a total of 63 wasp species). Our results form a continuum from species avoiding nesting on any plant (6.5% of the wasp species) to species nesting on plants but avoiding those sheltering ant nests (82%), to, finally, wasps nesting in association with arboreal ants known to divert army ant raids (11.5%). Consequently, this study documents that most wasp species select plants possibly repulsive to arboreal ants, while associations with arboreal ants, although confirmed here, have been overrepresented in the literature. To cite this article: B. Corbara et al., C. R. Biologies 332 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Polistinae; Diversity; Nest site selection; Ant-wasp-plant interactions; French Guiana
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McClure, M., Chouteau, M., & Dejean, A. (2008). Territorial aggressiveness on the arboreal ant Azteca alfari by Camponotus blandus in French Guiana due to behavioural constraints. C. R. Biol., 331(9), 663–667.
Abstract: This study reports new information on interactions between two sympatric ant species, the plant-ant Azteca alfari (Dolichoderinae) living in association with the myrmecophyte Cecropia obtusa (Cecropiaceae) and Camponotus blandus (Formicinae), a ground-nesting, arboreal-foraging species. Workers of A. alfari forage only on the foliage and the tipper parts of the trunk of their host Cecropia, while C. blandus nests in the ground but frequently forages and patrols pioneer tree foliage, including Cecropia. The activity pattern of A. alfari and the number of C. blandus on Cecropia obtusa was monitored hourly during a two-day period in a disturbed area in French Guiana. The maximum activity of C. blandus occurred between 8:30 and 12:30, at which time A. alfari had retreated within the domatia and were least present on the trunks. Even though aggressive confrontations were observed, C. blandus workers often initiate confrontations but do not prey on A. alfari nor exploit food bodies produced by Cecropia, the principal food source of A. alfari. Hence hostility appears to be the result of territoriality. Differences in their foraging rhythms are proposed as promoting resource and territory partitioning in this ant assemblage.
Keywords: Azteca alfari (Dolichoderinae); Camponotus blandus (Formicinae); foraging; rhythm of activity; territorial aggressiveness
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Maron, P. A., Schimann, H., Ranjard, L., Brothier, E., Domenach, A. M., Lensi, R., et al. (2006). Evaluation of quantitative and qualitative recovery of bacterial communities from different soil types by density gradient centrifugation. Eur. J. Soil Biol., 42(2), 65–73.
Abstract: Extracting and purifying a representative fraction of bacteria from soil is necessary for the application of many techniques of microbial ecology. Here the influence of different soil types on the quantitative and qualitative recovery of bacteria by soil grinding and Nycodenz density gradient centrifugation was investigated. Three soils presenting contrasted physicochemical characteristics were used for this study. For each soil, the total (AODC: acridine orange direct count) and culturable (cfa: colony-forming units) bacterial densities were measured in three distinct fractions: (i) the primary soil, (ii) the soil pellet (soil remaining after centrifugation), and (iii) the extracted cells. The automated-ribosomal intergenic spacer analysis (A-RISA) was used to characterize the community structure directly from the DNA extracted from each fraction. The physicochemical characteristics of soils were found to influence both the efficiency of bacterial cell recovery and the representativeness of the extracted cells in term of community structures between the different fractions. Surprisingly, the most representative extracted cells were obtained from the soil exhibiting the lowest efficiency of cell recovery. Our results demonstrated that quantitative and qualitative cell recovery using Nycodenz density gradient centrifugation are not necessarily related and could be differentially biased according to soil type. (c) 2006 Elsevier SAS. All rights reserved.
Keywords: bacterial community; soil; density gradient; DNA fingerprint
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Dejean, A., Moreau, C. S., Kenne, M., & Leponce, M. (2008). The raiding success of Pheidole megacephala on other ants in both its native and introduced ranges. C. R. Biol., 331(8), 631–635.
Abstract: We studied the behaviour of the invasive African myrmicine ant, Pheidole megacephala, when confronted with colonies of other common ant species in Cameroon, a part of its native range, and in Mexico, where it has been introduced. P. megacephala raided the nests of the other ants in both cases. Eleven species out of 12 put up a rather strong resistance to raiding P. megacephala workers in Cameroon compared to only three species out of 11 in Mexico, where only colonies of Solenopsis geminata, Dorymyrmex pyramicus and Dolichoderus bispinosus resisted these raids. We conclude that P. megacephala's heightened ability to successfully raid colonies of competing ants may help explain its success and the decline of native ants in areas where it has been introduced.
Keywords: invasive ants; predation; raiding other ants; recruitment
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Martin, J. M., Roux, O., Groc, S., & Dejean, A. (2011). A type of unicoloniality within the native range of the fire ant Solenopsis saevissima. C. R. Biol., 334(4), 307–310.
Abstract: To determine if a type of unicoloniality exists in the fire ant Solenopsis saevissima in its native range, we conducted intraspecific aggressiveness tests in French Guiana between workers originating from 15 human-disturbed sites. We identified two “colonial groups” spread over 54 km and 12.5 km, respectively. Workers from the same group never attacked each other, but inter-group confrontations resulted in a high level of aggressiveness. These large “colonial groups” enhances the threat occasioned by S. saevissima for both agriculture and the environment. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Ants; Solenopsis saevissima; Native range; Unicoloniality
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Hattenschwiler, S., Fromin, N., & Barantal, S. (2011). Functional diversity of terrestrial microbial decomposers and their substrates. C. R. Biol., 334(5-6), 393–402.
Abstract: The relationship between biodiversity and biogeochemical processes gained much interest in light of the rapidly decreasing biodiversity worldwide. In this article, we discuss the current status, challenges and prospects of functional concepts to plant litter diversity and microbial decomposer diversity. We also evaluate whether these concepts permit a better understanding of how biodiversity is linked to litter decomposition as a key ecosystem process influencing carbon and nutrient cycles. Based on a literature survey, we show that plant litter and microbial diversity matters for decomposition, but that considering numbers of taxonomic units appears overall as little relevant and less useful than functional diversity. However, despite easily available functional litter traits and the well-established theoretical framework for functional litter diversity, the impact of functional litter diversity on decomposition is not yet well enough explored. Defining functional diversity of microorganisms remains one of the biggest challenges for functional approaches to microbial diversity. Recent developments in microarray and metagenomics technology offer promising possibilities in the assessment of the functional structure of microbial communities. This might allow significant progress in measuring functional microbial diversity and ultimately in our ability to predict consequences of biodiversity loss in the decomposer system for biogeochemical processes. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Bacteria; Biogeochemical cycles; Decomposition; Dissimilarity; Ecosystem functioning; Functional diversity indices; Fungi; Leaf litter
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Masse, P. S. M., Kenne, M., Mony, R., Dejean, A., & Tindo, M. (2011). Initial behavior in colony fragments of an introduced population of the invasive ant Wasmannia auropunctata. C. R. Biol., 334(7), 572–576.
Abstract: We investigated in the laboratory the initial behavior of propagules of the invasive ant Wasmannia auropunctata in Cameroon where it has been introduced. Both workers and queens at first feigned death (thanatosis), and then the workers slowly moved around the experimental arena; the queens did the same about 10 seconds later. Each queen antennated selected workers that then aggregated together by grasping the hind leg of another ant with their mandibles. When encountering the queen again, the lead worker climbed up the queen's hind leg and onto her back, followed by some other individuals. The remaining workers followed the queen to a location in the experimental arena. When brood was present, the workers transferred it to this location. Orphaned workers did not aggregate, but gathered the brood together and took care of it. By permitting propagules to survive, these behaviors likely contribute to the success of W. auropunctata as an invader. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
Keywords: Aggregation; Death feigning; Thanatosis; Worker transportation; Biological invasion; Little fire ant
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Groc, S., Delabie, J. H. C., Cereghino, R., Orivel, J., Jaladeau, F., Grangier, J., et al. (2007). Ant species diversity in the 'Grands Causses' (Aveyron, France): In search of sampling methods adapted to temperate climates RID C-4034-2011. C. R. Biol., 330(12), 913–922.
Abstract: This study aimed at showing the applicability of using a combination of four sampling methods (i.e., Winkler extractors, pitfall traps, baiting and manual collection), something most often conducted in the tropics, to create an inventory of ant species diversity in temperate environments. We recorded a total of 33 ant species in the Grands Causses by comparing three vegetal formations: a steppic lawn ('causse' sensu stricto), which was the most species-rich (29 species), followed by an oak grove (22 species) and a pine forest (17 species). No sampling method alone is efficient enough to provide an adequate sampling, but their combination permits one to make a suitable inventory of the myrmecofauna and to obtain information on the ecology of these ant species.
Keywords: ant diversity; Grands Causses; sampling methods; temperate climate
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