Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth.
PLoS ONE

hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399
https://hal.archives-ouvertes.fr/hal-00912399/document
DOI : 10.1371/journal.pone.0020538
OATAO : 10156

Éditeur(s) : HAL CCSD Wiley
Résumé :  
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. 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 1.2 mm per 10 cm increase in stem diameter, and varied widely at all taxonomic levels. Mean trunk bark thickness was 4.5 mm (range: 0.5-29 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. 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. 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. 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.
ISSN: 0269-8463

hal-01032124
https://hal.archives-ouvertes.fr/hal-01032124
DOI : 10.1111/j.1365-2435.2010.01736.x

Éditeur(s) : HAL CCSD Royal Society, The
Résumé : Species engaged in multiple, simultaneous mutualisms are subject to trade-offs in their mutualistic investment if the traits involved in each interaction are overlapping, which can lead to conflicts and affect the longevity of these associations. We investigate this issue via a tripartite mutualism involving an ant plant, two competing ant species and a fungus the ants cultivate to build galleries under the stems of their host plant to capture insect prey. The use of the galleries represents an innovative prey capture strategy compared with the more typical strategy of foraging on leaves. However, because of a limited worker force in their colonies, the prey capture behaviour of the ants results in a trade-off between plant protection (i.e. the ants patrol the foliage and attack intruders including herbivores) and ambushing prey in the galleries, which has a cascading effect on the fitness of all of the partners. The quantification of partners' traits and effects showed that the two ant species differed in their mutualistic investment. Less investment in the galleries (i.e. in fungal cultivation) translated into more benefits for the plant in terms of less herbivory and higher growth rates and vice versa. However, the greater vegetative growth of the plants did not produce a positive fitness effect for the better mutualistic ant species in terms of colony size and production of sexuals nor was the mutualist compensated by the wider dispersal of its queens. As a consequence, although the better ant mutualist is the one that provides more benefits to its host plant, its lower host–plant exploitation does not give this ant species a competitive advantage. The local coexistence of the ant species is thus fleeting and should eventually lead to the exclusion of the less competitive species.
ISSN: 0962-8452

hal-01608641
https://hal.archives-ouvertes.fr/hal-01608641
DOI : 10.1098/rspb.2016.1679
PRODINRA : 405078

Éditeur(s) : Gauthier-Villars
Résumé : The biology and ecology of the green tropical algae Caulerpa taxifolia (Vahl) C. Agardh have been studied in the lagoons of New Caledonia (South Pacific) with a view to understanding the invasion which began in 1984 in the northwest Mediterranean Sea. A total of 1772 stations were used to establish the spatial and depth distribution of this species, which can be considered as common in New Caledonia, since it has been found in 9 % of the stations. C. taxifolia occurred mainly at depths between 10 and 30 m. Monthly sampling has shown that its growth is maximum during the southern hemisphere spring. From 180 stations randomly sampled in the southwest lagoon we obtained a mean biomass of 0.046 g afdw/m(2), which accounts for only 0.18 % of the macrophytobenthic biomass in this lagoon. Nevertheless the species constitutes a food source which is specific to the small herbivorous mollusc sacoglosses.
Oceanologica Acta (0399-1784) (Gauthier-Villars), 1994 , Vol. 17 , N. 5 , P. 563-569

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00099/21013/18639.pdf
http://archimer.ifremer.fr/doc/00099/21013/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The extent to which Marine Protected Areas (MPAs) benefit corals is contentious. On one hand, MPAs could enhance coral growth and survival through increases in herbivory within their borders; on the other, they are unlikely to prevent disturbances, such as terrestrial runoff , that originate outside their boundaries. We examined the effect of spatial protection and terrestrial sediment on the benthic composition of coral reefs in Saint Lucia. In 2011 (10 to 16 years after MPAs were created), we resurveyed 21 reefs that had been surveyed in 2001 and analyzed current benthic assemblages as well as changes in benthic cover over that decade in relation to protection status, terrestrial sediment influence (measured as the proportion of terrigenous material in reef-associated sediment) and depth. The cover of all ben-thic biotic components has changed significantly over the decade, including a decline in coral and increase in macroalgae. Protection status was not a significant predictor of either current benthic composition or changes in composition, but current cover and change in cover of several components were related to terrigenous content of sediment deposited recently. Sites with a higher proportion of terrigenous sediment had lower current coral cover, higher macroalgal cover and greater coral declines. Our results suggest that terrestrial sediment is an important factor in the recent degradation of coral reefs in Saint Lucia and that the current MPA network should be complemented by measures to reduce runoff from land.
ISSN: 1932-6203

hal-01281152
https://hal-univ-perp.archives-ouvertes.fr/hal-01281152
https://hal-univ-perp.archives-ouvertes.fr/hal-01281152/document
https://hal-univ-perp.archives-ouvertes.fr/hal-01281152/file/journal.pone.0146855.PDF
DOI : 10.1371/journal.pone.0146855

Éditeur(s) : HAL CCSD Wiley
Résumé : Understanding the mechanisms generating species distributions remains a challenge, especially in hyperdiverse tropical forests. We evaluated the role of rainfall variation, soil gradients and herbivory on seedling mortality, and how variation in seedling performance along these gradients contributes to habitat specialisation. In a 4-year experiment, replicated at the two extremes of the Amazon basin, we reciprocally transplanted 4638 tree seedlings of 41 habitat-specialist species from seven phylogenetic lineages among the three most important forest habitats of lowland Amazonia. Rainfall variation, flooding and soil gradients strongly influenced seedling mortality, whereas herbivory had negligible impact. Seedling mortality varied strongly among habitats, consistent with predictions for habitat specialists in most lineages. This suggests that seedling performance is a primary determinant of the habitat associations of adult trees across Amazonia. It further suggests that tree diversity, currently mostly harboured in terra firme forests, may be strongly impacted by the predicted climate changes in Amazonia.
ISSN: 1461-023X

hal-01531751
https://hal.archives-ouvertes.fr/hal-01531751
DOI : 10.1111/ele.12661
PRODINRA : 387284

Éditeur(s) : Inter-research
Résumé : We propose a statistical approach based on multivariate analysis and general linear models to test the consequences of removal of reserve status from the Abore Reef fish assemblage of the Abore Reef reserve, New Caledonia. Consequences on fish density were examined at the level of fish assemblage, accounting for habitat. Fish counts and habitat-related information were collected before and after the removal of reserve status, both inside and outside the reserve. Species groups were constructed on the basis of additional information on behavioural characteristics and taxonomy. The impact of the removal of reserve status was assessed by using 2 habitat proxies corresponding to 2 spatial scales and by considering several criteria for grouping species. Habitat appeared to be a determining factor in explaining density variations. Significant positive effects were found for several species groups such as macrocarnivores, piscivores, herbivores, Lethrinidae and Siganidae. A counterintuitive negative effect was observed for Acanthuridae. No significant differences between the area which remained closed to fishing and the area open to fishing were found for the other species groups. The approach allows for a synoptic diagnosis of the impact of changes in reserve status at the fish assemblage level. It could be used to develop and select potential indicators for monitoring such impacts on fish assemblages in coral reef ecosystems and in other contexts.
Marine Ecology Progress Series (0171-8630) (Inter-research), 2005 , Vol. 292 , P. 271-286

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00000/10970/7574.pdf
http://archimer.ifremer.fr/doc/00000/10970/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
While the populations of large herbivores are being depleted in many tropical rainforests, the importance of their trophic role in the ecological functioning and biodiversity of these ecosystems is still not well evaluated. This is due to the outstanding plant diversity that they feed upon and the inherent difficulties involved in observing their elusive behaviour. Classically, the diet of elusive tropical herbivores is studied through the observation of browsing signs and macroscopic analysis of faeces or stomach contents. In this study, we illustrate that the original coupling of classic methods with genetic and ethnobotanical approaches yields information both about the diet diversity, the foraging modalities and the potential impact on vegetation of the largest terrestrial mammal of Amazonia, the lowland tapir. The study was conducted in the Guianan shield, where the ecology of tapirs has been less investigated. We identified 92 new species, 51 new genera and 13 new families of plants eaten by tapirs. We discuss the relative contribution of our different approaches, notably the contribution of genetic barcoding, used for the first time to investigate the diet of a large tropical mammal, and how local traditional ecological knowledge is accredited and valuable for research on the ecology of elusive animals.
ISSN: 1932-6203

halsde-00676374
https://hal.archives-ouvertes.fr/halsde-00676374
DOI : 10.1371/journal.pone.0025850
PUBMED : 21991372

Éditeur(s) : Soc Francaise D Ichtyologie
Résumé : The ichtyofauna of Geyser and Zelee coral banks (north of Mozambique canal) was investigated in 1996, this work being the first quantitative study on this area. Quantitative data were collected on 11 stations (mean depth 18 m) by visual observations along 50 m transect, widened to 2 m for small sedentary species, and to 5 m for commercial species with a large action range. The main descriptors of the fish communities (species richness, abundance per species) and the trophic structure (omnivorous, herbivorous, carnivorous, browsers of sessile invertebrates) were described and analysed.A total of 294 fish species, belonging to 43 families were recorded. The species richness varied from 45 to 83 species / station, and the abundance, from 292 to 1322 individuals / 100 m(2), the lower values being recorded on the inner slope and the higher ones on the outer slope. In terms of number of individuals, diurnal planktivores were highly represented at all sites (mean 63.7%). Pomacentridae and Caesionidae were the most abundant families, damselfishes being mainly represented by Chromis ternatensis (mean 73 ind., max, 148 ind. 100 m(2)), C. dimidiata (mean 33 ind., max. 151 ind. / 100 m(2)) and Dascyllus carneus (mean 38 ind., max. 92 ind. 100 m(2)), and fusiliers by Pterocaesio chrysozona (mean 19 ind., max. 128 ind. / 100 m(2)), P. tile (mean 12 ind., max. 38 ind. / 100 m(2)) and Caesio teres (mean 6 ind., max. 32 ind. / 100 m(2)). The high values recorded showed that small and isolated coral banks can support relatively rich fish faunas and substantial populations of individuals. This result may be explained by different factors such as the oceanographic circulation favourable to a localised enrichment of nutrients from surface water, the low human impact, a good coral cover and a high degree of self-recruitment associated with regional recruitment. Nevertheless, the main commercial species such as Lutjanus bohar and Variola louti, observed at each station, were represented at a low density (mean 0.8 ind., max. 6 ind. / 100 m(2) and mean 0.2 ind., max. 0.8 ind. / 100 m(2) respectively). This result may be due to the exploitation of these coral banks between 1990 and 1992, which was interrupted following the fast decreasing output.Such an experience shows us the fragility of these small coral banks and the necessity to establish a rational management of the resource.
Cybium (0399-0974) (Soc Francaise D Ichtyologie), 2002 , Vol. 26 , N. 1 , P. 11-26

Droits : info:eu-repo/semantics/openAccess
http://archimer.ifremer.fr/doc/00000/10132/7687.pdf
http://archimer.ifremer.fr/doc/00000/10132/

Éditeur(s) : HAL CCSD American Association for the Advancement of Science
Résumé : International audience
Most eukaryotic organisms are arthropods. Yet, their diversity in rich terrestrial ecosystems is still unknown. Here we produce tangible estimates of the total species richness of arthropods in a tropical rainforest. Using a comprehensive range of structured protocols, we sampled the phylogenetic breadth of arthropod taxa from the soil to the forest canopy in the San Lorenzo forest, Panama. We collected 6144 arthropod species from 0.48 hectare and extrapolated total species richness to larger areas on the basis of competing models. The whole 6000-hectare forest reserve most likely sustains 25,000 arthropod species. Notably, just 1 hectare of rainforest yields >60% of the arthropod biodiversity held in the wider landscape. Models based on plant diversity fitted the accumulated species richness of both herbivore and nonherbivore taxa exceptionally well. This lends credence to global estimates of arthropod biodiversity developed from plant models.
ISSN: 0036-8075

hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285
https://hal.archives-ouvertes.fr/hal-00817285/document
https://hal.archives-ouvertes.fr/hal-00817285/file/1226727Revisedtext.pdf
DOI : 10.1126/science.1226727

Éditeur(s) : HAL CCSD Universidad Complutense de Madrid
Résumé : The Lodève Permian synrift sequence is represented by thick stacked climate-controled playa cycles which have been constrained by structural, sedimentological, geochemical and paleontological processes. The present paper merges the different results in order to better constrain the dynamics and palaeoecologycal evolution of the playa system from Late Cisuralian to Early Lopingian time. In this depositional environment, thining upwards sheet-flood sequences represent flooding events; they are relayed by ephemeral ponding, suspension settling and limited carbonate precipitation accompanied by large amounts of shallow to subaerial sedimentary structures... (Ver más) (current and wind ripples, desiccation cracks, rain drops, etc.). The aridity of the climate contrasts with the surprising abundance of the fauna encountered into carbonate-rich silty-clay playa-lake deposits. Ephemeral pools are colonized by numerous shellfish: Choncostraca, Triopsids, and Insects, which led to intense burrowing of the overbank deposits (Scoyenia facies). Tetrapods are common and dominated by several types of reptiles after footprints: Pelycosauria, Parareptilia and Lepidosauria in the Rabejac Fm, and Mammalian reptiles (Therapsida) on the top of the fluvial deposits of the Salagou Fm near La Lieude farm. In addition, elements of a weighty herbivorous Pelycosaurian and a small amphibian Tupilakosaurid, only described in the Triassic before, have been also found in the Upper part of the Permian series of this sector.
ISSN: 1698-6180

hal-00411539
https://hal.archives-ouvertes.fr/hal-00411539

Éditeur(s) : HAL CCSD Botanical Society of America
Résumé :  
To investigate the existence of coordinated sets of seedling traits adapted to contrasting establishment conditions, we examined evolutionary convergence in seedling traits for 299 French Guianan woody plant species and the stress response in a shadehouse of species representing seed size gradients within five major cotyledon morphology types. The French Guianan woody plant community has larger seeds than other tropical forest communities and the largest proportion of hypogeal cotyledon type (59.2%) reported for tropical forests. Yet the community includes many species with intermediate size seeds that produce seedlings with different cotyledonal morphologies. A split-plot factorial design with two light levels (0.8% and 16.1% PAR) and four damage treatments (control, seed damage, leaf damage, stem damage) was used in the shadehouse experiment. Although larger-seeded species had higher survival and slower growth, these patterns were better explained by cotyledon type than by seed mass. Even larger-seeded species with foliar cotyledons grew faster than species with reserve-type cotyledons, and survival after stem grazing was five times higher in seedlings with hypogeal cotyledons than with epigeal cotyledons. Thus, to predict seedling performance using seed size, seedling morphology must also be considered.
ISSN: 0002-9122

hal-01032177
https://hal.archives-ouvertes.fr/hal-01032177
DOI : 10.3732/ajb.94.6.901

Éditeur(s) : HAL CCSD Wiley Open Access
Résumé : International audience
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.
ISSN: 2045-7758

Droits : http://creativecommons.org/licenses/by/
hal-01296640
http://hal.upmc.fr/hal-01296640
http://hal.upmc.fr/hal-01296640/document
http://hal.upmc.fr/hal-01296640/file/ece31810.pdf
DOI : 10.1002/ece3.1810

Éditeur(s) : HAL CCSD
Résumé : Biogenic volatile organic compound (BVOCs) emissions play an important role in regional air quality and global atmospheric chemistry. In addition, these natural VOC emissions serve important biological functions including attracting and repelling pollinators and herbivores. Some biological organisms use ambient air as a communication medium and the oxidation of these compounds brings about the concentration gradients sensed by insects and other organisms. Isoprene is the predominant BVOC emitted by vegetation and tropical forests are the dominant global source. This compound is very reactive in the atmosphere and contributes to the reactions that control tropospheric oxidant concentrations and thus the concentrations and lifetimes of longer-lived species. This paper presents a study on the seasonal variations in isoprene and some other significant BVOCs such as µ-pinene, µ-pinene, limonene, e-µ ocimene and longifolene, measured at the Guyaflux Tower located in a wet tropical forest in Paracou French Guiana (5o16´54´´N, 52o54´44´´W), during the year of 2011, using the Relaxed Eddy Accumulation technique at approximately 20 meters high above the canopy. The results show a lower concentration of isoprene during the month of February and March which correspond to the wet season with an average of 0,545 µg/m3 and 0,341 µg/m3, respectively followed by a slight increase in middle April (still wet season) and a higher concentration later in mid-June. The same behavior was observed for µ-pinene with higher concentrations for the same periods as isoprene however with a smaller increase. All the other compounds had concentrations below 1 µg/m3during the whole year: The monoterpene, e-µ ocimene, was observed and is known as a stress compound but the vegetation at the site did not face any known severe stress condition such as excessive drought or flooding. Concerning the fluxes, the results showed that just a small amount of BVOCs were deposited by wet or dry process and the majority of them were released in the atmosphere. Isoprene was by far the biogenic volatile organic compound with the highest concentration and flux, followed by alpha-pinene. The lowest concentration and flux rate for all the studied compounds was observed during the months of March and late July and beginning of August indicating a lower production of those BVOCs by vegetation during those periods. Previous limited studies in Amazonia and the Congo suggested that a higher concentration and flux rate of isoprene and µ-pinene should be expected during the dry season with lower emissions during the wet season, which is in relative agreement with what was observed at this tropical forest site in French Guiana. The exceptions were observed in April and June which correspond to a long wet period in which the concentration of isoprene and µ-pinene increased more than it was expected for this time of the year. The observations will be compared to output from the global chemistry transport model CAM-chem, which includes the MEGAN biogenic emissions model.
10th EGU General Assembly
vienne, Austria

hal-01204214
https://hal.archives-ouvertes.fr/hal-01204214
PRODINRA : 276525

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ¹⁵N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms.
PLoS ONE

hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754
https://hal.archives-ouvertes.fr/hal-00913754/document
DOI : 10.1371/journal.pone.0059405
OATAO : 10202

Éditeur(s) : HAL CCSD Wiley
Résumé : In the Amazon basin and the Guiana Shield, white-sand (WS) forests are recognized as a low-resource habitat often composed by a distinct flora with many edaphic endemic plants. Small patches of nutrient-poor white-sand forests can pose a series of challenges to plants and animals. For plants, these challenges have been shown to function as strong filters that in turn drive taxonomic, functional and phylogenetic plant composition. However, very little is known about animal communities in WS forest and the effect that low-resource availability may have on higher trophic levels. Here, we investigate the diversity of both taxonomic and phylogenetic diversity of three Lepidoptera families' (Nymphalidae, Saturniidae, and Sphingidae) assemblages between low-resource (White-Sand Forest) and two adjacent high-resource habitats, terra firme clay and seasonally flooded forests. We found no clear effect of habitat type on taxonomic composition although butterfly and moth species abundance differed among the three contrasted habitats. The WS forest Lepidoptera community is significantly more phylogenetically overdispersed than expected by chance. We suggest that these low-resource habitats filter the number of plant lineages which, in turn, creates a bottom-up control structuring Lepidoptera phylogenetic structure. We recommend long-term sampling on Lepidoptera community both at larval and adult stages that may complement this study and test hypotheses linking herbivore phylogenetic structure to plant resource availability and trophic cascade theory.
ISSN: 0006-3606

hal-01532550
https://hal.archives-ouvertes.fr/hal-01532550
DOI : 10.1111/btp.12294
PRODINRA : 353400

Éditeur(s) : Cambridge Univ Press
Résumé : Integrated Multi-Trophic Aquaculture takes advantage of the mutualism between some detritivorous fish and phytoplankton. The fish recycle nutrients by consuming live (and dead) algae and provide the inorganic carbon to fuel the growth of live algae. In the meanwhile, algae purify the water and generate the oxygen required by fishes. Such mechanism stabilizes the functioning of an artificially recycling ecosystem, as exemplified by combining the euryhaline tilapia Sarotherodon melanotheron heudelotii and the unicellular alga Chlorella sp. Feed addition in this ecosystem results in faster fish growth but also in an increase in phytoplankton biomass, which must be limited. In the prototype described here, the algal population control is exerted by herbivorous zooplankton growing in a separate pond connected in parallel to the fish-algae ecosystem. The zooplankton production is then consumed by tilapia, particularly by the fry and juveniles, when water is returned to the main circuit. Chlorella sp. and Brachionus plicatilis are two planktonic species that have spontaneously colonized the brackish water of the prototype, which was set-up in Senegal along the Atlantic Ocean shoreline. In our system, water was entirely recycled and only evaporation was compensated (1.5% volume/day). Sediment, which accumulated in the zooplankton pond, was the only trophic cul-de-sac. The system was temporarily destabilized following an accidental rotifer invasion in the main circuit. This caused Chlorella disappearance and replacement by opportunist algae, not consumed by Brachionus. Following the entire consumption of the Brachionus population by tilapias, Chlorella predominated again. Our artificial ecosystem combining S. m. heudelotii, Chlorella and B. plicatilis thus appeared to be resilient. This farming system was operated over one year with a fish productivity of 1.85 kg/m(2) per year during the cold season (January to April).
Animal (1751-7311) (Cambridge Univ Press), 2013-02 , Vol. 7 , N. 2 , P. 322-329

Droits : The Animal Consortium 2012
http://archimer.ifremer.fr/doc/00118/22955/20945.pdf
DOI:10.1017/S1751731112001279
http://archimer.ifremer.fr/doc/00118/22955/

Éditeur(s) : HAL CCSD eLife Sciences Publication
Résumé : International audience
Larval recruitment, the transition of pelagic larvae into reef-associated juveniles, is a critical step for the resilience of marine fish populations but its molecular control is unknown. Here, we investigate whether thyroid-hormones (TH) and their receptors (TR) coordinate the larval recruitment of the coral-reef-fish Acanthurus triostegus. We demonstrate an increase of TH-levels and TR-expressions in pelagic-larvae, followed by a decrease in recruiting juveniles. We generalize these observations in four other coral reef-fish species. Treatments with TH or TR-antagonist, as well as relocation to the open-ocean, disturb A. triostegus larvae transformation and grazing activity. Likewise, chlorpyrifos, a pesticide often encountered in coral-reefs, impairs A. triostegus TH-levels, transformation, and grazing activity, hence diminishing this herbivore’s ability to control the spread of reef-algae. Larval recruitment therefore corresponds to a TH-controlled metamorphosis, sensitive to endocrine disruption. This provides a framework to understand how larval recruitment, critical to reef-ecosystems maintenance, is altered by anthropogenic stressors.
ISSN: 2050-084X

Droits : http://creativecommons.org/licenses/by/
hal-01633712
http://hal.upmc.fr/hal-01633712
http://hal.upmc.fr/hal-01633712/document
http://hal.upmc.fr/hal-01633712/file/elife-27595-v1.pdf
DOI : 10.7554/eLife.27595

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
Tropical plants frequently live in association with ants that protect their foliage from defoliators. Among them, myrmecophytes have evolved mutualisms with a limited number of plant-ants that they shelter and feed, and, in return, benefit from some protection. Hirtella physophora (Chrysobalanaceae), for example, houses Allomerus decemarticulatus (Myrmicinae) that build gallery-shaped traps to catch large prey. In French Guiana, we frequently observed the assassin bug Zelus annulosus (Reduviidae, Harpactorinae) on the leaves of H. physophora. Here, we studied the distribution of Zelus annulosus among understory plants in the Guianese rainforest and found it only on pubescent plants, including H. Physophora, whether or not it was sheltering an A. decemarticulatus colony, but only rarely on other myrmecophytes. The relationship between Z. annulosus and its host plants is, then, also mutualistic, as the plant trichomes act as an enemy-free space protecting the nymphs from large predatory ants, while the nymphs protect their host-plants from herbivorous insects. Through their relationship with A. decemarticulatus colonies, Z. annulosus individuals are protected from army ants, while furnishing nothing in return. In those cases where H. physophora sheltered both an A. decemarticulatus colony and Z. annulosus nymphs, certain plant individuals repeatedly sheltered nymphs, indicating that female bugs may select not only pubescent plants but also particular H. physophora treelets having characteristics more favourable to the development of their progeny.
PLoS ONE

hal-00911249
https://hal.archives-ouvertes.fr/hal-00911249
https://hal.archives-ouvertes.fr/hal-00911249/document
DOI : 10.1371/journal.pone.0013110
OATAO : 10144

Éditeur(s) : HAL CCSD Springer Verlag
Résumé : International audience
Introduction The Latitudinal Gradient Hypothesis (LGH) foresees that specialized metabolites are overexpressed under low latitudes, where organisms are subjected to higher herbivory pressure. The widespread macroalga Asparagopsis taxiformis is composed of six distinct genetic lineages, some of them being introduced in many regions. Objectives To study (i) metabolic fingerprints of the macroalga and (ii) its bioactivity in space and time, both as proxies of its investment in defensive traits, in order to assess links between bioactivities and metabotypes with macroalgal invasiveness. Methods 289 macroalgal individuals, from four tropical and three temperate regions, were analyzed using untargeted metabolomics and the standardized Microtox (R) assay. Results Metabotypes showed a low divergence between tropical and temperate populations, while bioactivities were higher in temperate populations. However, these phenotypes varied significantly in time, with a higher variability in tropical regions. Bioactivities were high and stable in temperate regions, whereas they were low and much variable in tropical regions. Although the introduced lineage two exhibited the highest bioactivities, this lineage could also present variable proliferation fates. Conclusion The metabolomic approach partly discriminates macroalgal populations from various geographic origins. The production of chemical defenses assessed by the bioactivity assay does not match the macroalgal genetic lineage and seems more driven by the environment. The higher content of chemical defenses in temperate versus tropical populations is not in accordance with the LGH and cannot be related to the invasiveness of the macroalgae.
ISSN: 1573-3882

hal-01681538
https://hal.archives-ouvertes.fr/hal-01681538
DOI : 10.1007/s11306-017-1169-z