Ants are widely regarded as ecosystem engineers because of their effect on soil structure and on the flow of energy. However, little is known about their influence on the carbon flux in tropical ...humid savannah. Recent investigations in a humid savannah ecosystem in Lamto showed that ant nests’ association with perennial grasses enhances their growth and productivity. This study aimed at understanding the influence of ant nests on soil micro‐organism's activity beneath grass tufts. The kinetic of mineralisation was tested in laboratory conditions at various times (days 1, 2, 4 and 7) beneath three grass species associated and not associated with ant nests, following the CO2 amount released at 30℃ during soil respiration. The amount of CO2 released from the soil is higher beneath grass tufts associated with ant nests compared with those not associated with ant nest. The highest amount of CO2 released from the soil was found beneath Hyparrhenia diplandra tufts followed by Andropogon schirensis tufts and the lowest under Loudetia simplex tufts. This study has shown that ant nests’ association with grass tufts enhances microbial activity in this savannah ecosystem.
Résumé
Les fourmis sont largement considérées comme des ingénieurs de l'écosystème en raison de leur effet sur la structure du sol et sur le flux d'énergie. Cependant, on sait peu de choses sur leur influence sur le flux de carbone dans les savanes tropicales humides. Des études récentes dans un écosystème de savane humide à Lamto ont montré que l'association des nids de fourmis avec des herbes pérennes améliore leur croissance et leur productivité. Cette étude visait à comprendre l'influence des nids de fourmis sur l'activité des microorganismes du sol sous les touffes d'herbe. La cinétique de minéralisation a été testée en laboratoire à différents moments (jour 1, 2, 4 et 7) sous trois espèces de graminées associées et non associées à des nids de fourmis, en suivant la quantité de CO2 libérée à 30°C pendant la respiration du sol. La quantité de CO2 libérée du sol est plus élevée sous les touffes d'herbes associées aux nids de fourmis que sous celles qui ne le sont pas. La plus grande quantité de CO2 libérée du sol a été trouvée sous les touffes d'Hyparrhenia diplandra, suivie par les touffes d'Andropogon schirensis et la plus faible sous les touffes de Loudetia simplex. Cette étude a montré que l'association des nids de fourmis avec les touffes d'herbe améliore l'activité microbienne dans cet écosystème de savane.
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Ants are known to contribute to the physical and chemical improvement of the soil. In this context, the hypothesis put forward is that ants improve the nitrogen (N) supplementation necessary to ...ensure the high primary production measured in the Lamto savannah. Recent investigations in the humid savannah ecosystem showed that ant nests’ association with perennial grasses enhances their growth, productivity, and microorganism activity. This study aimed at understanding the effect of ant nests on organic matter (OM), carbon (C), and N flux beneath grass tufts. Under each grass tuft chosen to carry out this study, soil samples were taken from the depths of 0–10 cm using an auger at shrubby, clear grassy, and transitional grassy savannah. The analytical method by incineration of the loss on fire was used to determine the OM amount. The Kjeldahl method was used to determine the total N amount in the soil under grass tufts. The results showed that these components’ amount is higher beneath grass tufts associated with ant nests than those not associated with ant nests. The presence of ant nests increases OM and C amount in the soil under Hyparrhenia diplandra tufts than Andropogon schirensis, and Loudetia simplex tufts. In contrast, N amount is higher under L. simplex tufts than A. schirensis; but mean under H. diplandra. The carbon/nitrogen ratios less than 10 indicate high OM mineralization under grass tufts associated with ant nests. This provides the plants with an adequate supply of nutrients.
Core Ideas
Ants improve the nitrogen (N) supplementation necessary to ensure high primary production measured in the Lamto savannah.
This study aimed at understanding the effect of ant nests on organic matter (OM), carbon (C), and N flux beneath grasses.
The carbon/nitrogen ratios less than 10 indicate high OM mineralization under grasses associated with ant nests.
OM capacity to decompose more or less rapidly and the absorption of N is released into the soil under grass tufts.
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In this study the taxonomy of the
Pheidole pulchella
species group is updated for the Afrotropical region and the new species
P. klaman
sp. nov.
described. It is integrated into the existing ...taxonomic system by an updated identification key for the whole group and an update of the known distribution ranges of its members. High quality focus stacking images are provided, with X–ray micro–CT scanned digital 3D representations, of major and minor worker type specimens.
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Context.
Dusty debris disks around pre- and main-sequence stars are potential signposts for the existence of planetesimals and exoplanets. Giant planet formation is therefore expected to play a key ...role in the evolution of the disk. This is indirectly confirmed by extant submillimeter near-infrared images of young protoplanetary and cool dusty debris disks around main-sequence stars that usually show substantial spatial structures. With two decades of direct imaging of exoplanets already studied, it is striking to note that a majority of recent discoveries of imaged giant planets have been obtained around young early-type stars hosting a circumstellar disk.
Aims.
Our aim was to create a direct imaging program designed to maximize our chances of giant planet discovery and target 22 young early-type stars. About half of them show indications of multi-belt architectures.
Methods.
Using the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-constrast coronagraphic differential near-infrared images, we conducted a systematic search in the close environment of these young, dusty, and early-type stars. We used a combination of angular and spectral differential imaging to reach the best detection performances down to the planetary mass regime.
Results.
We confirm that companions detected around HIP 34276, HIP 101800, and HIP 117452 are stationary background sources and binary companions. The companion candidates around HIP 8832, HIP 16095, and HIP 95619 are determined as background contaminations. Regarding the stars for which we infer the presence of debris belts, a theoretical minimum mass for planets required to clear the debris gaps can be calculated. The dynamical mass limit is at least 0.1
M
J
and can exceed 1
M
J
. Direct imaging data is typically sensitive to planets down to ~3.6
M
J
at 1′′, and 1.7
M
J
in the best case. These two limits tightly constrain the possible planetary systems present around each target. These systems will be probably detectable with the next generation of planet imagers.
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Estuarine and wetland ecosystems are becoming increasingly altered by the concentration of human population near the coastline. A major threat to biodiversity related to this human footprint is the ...introduction of invasive alien species, particularly in isolated ecosystems like islands where biological invasion is often harmful. The National Park of Ehotilés Islands is an archipelago of 6 islands and a RAMSAR site subjected to disturbances activities like agriculture, illegal fisheries, and tourism. These factors often act as an accelerator for the introduction of invasive species. However, there is a lack of research conducted on insects, specifically ants on these islands. This study aimed to inventory the present ant fauna and estimate the vulnerability to tramp and potential invasive ant species. Ants were collected using Winkler, pitfall, and funnel traps on five islands. In total, 76 ant species were recorded. These species are distributed into 20 genera and five subfamilies: Dolichoderinae (5 species), Formicinae (11 species), Myrmicinae (49 species), Ponerinae (11 species) and Proceratiinae (1 species). We also detected two tramp and potentially invasive species: the ghost ant Tapinoma melanocephalum and the big-headed ant Pheidole megacephala. Ant communities are dominated by six species, namely Odontomachus troglodytes, Oecophylla longinoda, Nylanderia lepida, Pheidole sp.2, Monomorium invidium, and the invasive ghost ant Tapinoma melanocephalum. This work is the first to inventory ants on the Islands of Ehotilés National Park and may serve as a basis for conservation decisions as it demonstrates that this park is not spared from the introduction of invasive ant species.
In this study the taxonomy of the
species group is updated for the Afrotropical region and the new species
described. It is integrated into the existing taxonomic system by an updated identification ...key for the whole group and an update of the known distribution ranges of its members. High quality focus stacking images are provided, with X-ray micro-CT scanned digital 3D representations, of major and minor worker type specimens.
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Ants constitute an important part of arboreal arthropod biomass in rainforests. Nevertheless, there are only a few methods which permit a rapid assessment of these insects in the canopy layer. This ...study aims at evaluating the efficiency of a new variant type of pitfall trap i.e. “the funnel trap”, to sample arboreal ants in a secondary and gallery forest in Lamto reserve (Côte d’Ivoire). This method was compared to standard arboreal pitfall trap and beating. In total, the 3 methods yielded 7072 ant workers belonging to 43 species, 14 genera and 5 subfamilies. Tree beating recorded the highest ant’s numerical abundance (3670 workers), with 27 species, 12 genera and 3 subfamilies followed by the “funnel trap” that yielded 2800 ant workers, with 23 species belonging to 12 genera and 5 subfamilies. Finally, arboreal pitfall traps caught the lowest individual with 602 ant workers from 20 species belonging to 9 genera and 3 subfamilies. The composition of species which are caught by arboreal pitfall trap and “funnel trap” was similar at 53 percent. Tree beating showed a distinct species composition compared to arboreal pitfall trap and “funnel trap”. The “funnel trap” could be a fast and efficient way to quickly assess ant-biodiversity in forest canopies and agroecosystems as it looks like a non-destructive sampling method.
L’utilisation du dialysat citraté en HDF post-dilution (HDF-POST) est actuellement controversée. Un effet anticoagulant a été évoqué sans avoir été confirmé. De plus, l’hypocalcémie induite par le ...citrate oblige à augmenter la concentration en calcium du dialysat sans que les effets au long cours sur le métabolisme osseux ne soient connus. Dans ce travail, nous rapportons notre expérience d’un an d’utilisation.
Entre le 1er mai 2013 et le 31 avril 2014, tous les patients ayant été traités par bains citratés (Ca2+1,65mEq, citrate 1mm) en HDF-POST sur générateurs Gambro® (AK-200US et ARTIS) et pour lesquels une diminution de la nadroparine en séance a été réalisée ont été inclus dans cette étude rétrospective monocentrique. Les hémorragies et les coagulations ont été répertoriées ainsi que les données biologiques (calcémie, urée, hémoglobine et PTH) et les traitements administrés. Des tests non paramétriques et des analyses multivariées adaptées ont été utilisés afin d’analyser la survenue d’évènements indésirables et d’évaluer la possibilité d’arrêt de l’anticoagulation en séance.
Seules 2056 séances d’HDF-POST pour 27 patients ont été analysées. Les calcémies, la PTH ainsi que l’utilisation de carbonates de calcium ou d’EPO sont restées stables dans le temps. Soixante-seize coagulations en cours de séance ont été répertoriées et aucune hémorragie. Seuls 5 patients ont pu être dialysés de manière prolongée sans nadroparine, tous étaient traités par AVK. Après analyse multivariée, la diminution et l’arrêt de la nadroparine ont été identifiés comme facteurs de risque de coagulation en séance (RR 6,9–CI 95 % : 1.1–44, p=0,0396) alors que l’utilisation des AVK et les générateurs ARTIS ont été associés à un moindre risque de coagulation (p<0,001 et 0,021 respectivement).
L’utilisation d’un dialysat citraté en HDF-POST est sûr et n’induit pas de troubles du métabolisme osseux pour une concentration en calcium de 1,65mEq. Cependant, le dialysat au citrate ne permet pas de réaliser de séances sans anticoagulant.
Les dialysats citratés peuvent être utilisés en HDF-POST mais ne permettent pas l’arrêt de l’anticoagulation en séance.
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The use of soil and litter arthropods as biological indicators is a way to assess environmental changes, where ant species in particular may serve as important indicators of soil quality. This study ...aimed at relating the abundance of soil and litter ant species to soil parameters under different tree species, both native and exotic, and varieties of coffee and banana plantations. Variations were found in soil physicochemical parameters. A total of 30 species belonging to 14 genera, and four subfamilies, the Formicinae, Dorylinae, Myrmicinae, and Ponerinae were identified. Higher abundance was found in coffee plantations compared to banana plantations, exotic and native tree species. Species of Camponotus cinctellus and Odontomachus troglodytes occurred in all land uses which is a sign of tolerance to a wide range of soil properties. In addition, these species, together with Myrmicaria SP02, Phrynoponera gabonensis, Camponotus SP06, Myrmicaria opaciventris, Pheidole SP03, Tetramorium simillimum, Pheidole SP01, and Tetramorium laevithorax were not strongly correlated with soil physicochemical parameters. Species of Pheidole SP02 and Camponotus SP05 were restricted to specific soil physicochemical properties, while species of Tetramorium zonacaciae and Bothroponera talpa discriminated between native tree species, coffee plantations, soil organic carbon, sandy soil texture, and aggregate stability. We concluded that these ant species can differently indicate the soil quality depending on the land use. We recommended further studies in order to generalize these findings.
Abstract
In the tropical forest‐savannah mosaic of Lamto Reserve in Ivory Coast ants play an important role in the biodiversity conservation. This work aimed to explore the structure and composition ...of the arboreal ant assemblages in a forest‐savannah mosaic located in central Côte d'Ivoire. Ants were collected by baited trap (Protein bait: tuna and sugar bait: sweet milk) and beating of low vegetation. During the entire sampling campaign, 59 ant species belonging to 18 genera and five subfamilies (Formicinae, Ponerinae, Myrmicinae, Dolichoderinae and Pseudomyrmecinae) were recorded. The mean ant species richness of shrub savannah (SS) was significantly lower than of both forest island (FI) and forest gallery. Likewise, a significant difference was observed for species composition when comparing the arboreal ant communities of SS, gallery forest and FI.
Résumé
Dans la mosaïque forêt tropicale‐savane de la réserve de Lamto en Côte d'Ivoire, les fourmis jouent un rôle important dans la conservation de la biodiversité. Ce travail avait pour but d'explorer la structure et la composition des assemblages de fourmis arboricoles dans une mosaïque forêt‐savane située dans le centre de la Côte d'Ivoire. Les fourmis ont été collectées à l'aide de pièges appâtés (appât protéique : thon et appât sucré : lait sucré) et de battues de végétation basse. Pendant toute la campagne d'échantillonnage, 59 espèces de fourmis appartenant à 18 genres et cinq sous‐familles (Formicinae, Ponerinae, Myrmicinae, Dolichoderinae et Pseudomyrmecinae) ont été répertoriées. La richesse moyenne en espèces de fourmis de la savane arbustive (SA) était considérablement plus faible que celle de l'île forestière (IF) et de la galerie forestière. De même, une différence importante a été observée pour la composition des espèces en comparant les communautés de fourmis arboricoles de la SA, de la forêt‐galerie et de l'IF.
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