Second Record and DNA Barcode of the Ant Tyrannomyrmex rex Fernández (Hymenoptera: Formicidae: Myrmicinae)

Tyrannomyrmex is a rarely collected ant genus from Old World tropical forests comprising only three described species, all of them known from a single worker. Here we report the discovery of a second worker of Tyrannomyrmex rex from a selectively logged primary forest of Singapore, increasing the known distribution range of the species to nearly 250 km South-East. We also provide a DNA barcode for the species and a partial sequence of the wingless gene. Although insufficient evidence prevents us to draw any firm conclusion, the genus seems to be restricted to pristine or relatively undisturbed forests and, as a result, could be highly sensitive to habitat degradation

Capacité invasive d'Ips typographus et effet Allee -- Lutte biologique

Ips typographus est le ravageur le plus important des forêts européennes. Son hôte principal est l’épicéa, et en conditions endémiques il s’attaque à des arbres affaiblis ou des chablis. A la suite d’une catastrophe naturelle, comme une tempête ou une sécheresse prolongée, l’abondance de ressources peut mener à une explosion démographique, qui dépasse alors le seuil épidémique. Les attaques sont tellement nombreuses que les scolytes viennent à bout des défenses des arbres sains, et les tuent. L’importante capacité de dispersion de cet insecte est une adaptation essentielle à la découverte de ressources potentielles, disséminées dans le temps et l’espace. A l’émergence, les insectes vont alimenter un réservoir de population formé au-dessus du paysage par l’apport de multiples sources. Ce travail vise à mieux comprendre deux aspects complémentaires de la migration :• La dispersion à longue distance, grâce à l’analyse de la structure spatiale du réservoir, qui s’amenuise progressivement avec la distance aux sources. L’approche expérimentale est l’établissement d’un transect de 150 km entre la zone endémique, Bouillon, et une zone dépourvue d’épicéas, la Champagne. Les captures réalisées le long de ce transect montrent que le réservoir est capable de s’avancer bien au-delà de la zone endémique, et de se concentrer localement au niveau de peuplements isolés. • La dispersion à courte distance, en l’absence de réservoir local. A cette fin, une expérience de lâcher-recapture d’individus marqués a été réalisée dans une zone dépourvue d’épicéas :la Forêt Domaniale de la Perthe, en Champagne-Ardenne. Les résultats de recapture montrent que la dilution des individus émergeant d’une source unique est très rapide, et qu’en l’absence de réservoir, la colonisation de nouvelles ressources est certainement impossible. En outre, l’étude de l’effet du vol sur les réserves adipeuses a été réalisée au moyen d’un moulin de vol. Cette expérience a montré qu’un vol de moins de 5 km n’entame pas les réserves lipidiques.info:eu-repo/semantics/nonPublishe

Capacité invasive d'Ips typographus (Coleoptera, Curculionidae) et effet Allee

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Facteurs déterminant la distribution spatio-temporelle des fourmis dans une forêt tropicale andine

In tropical forests, ants are numerous, diversified and ecologically important, being present from forest floor to upper canopy and exploiting a wide variety of diets. Nearly half of the ant species are directly in contact with the ground stratum, including the leaf-litter and the underlying soil, for nesting or foraging. The main factors known to influence ant distribution and abundance can be environmental (e.g. heterogeneous distribution of microhabitat size, nutrient availability, microclimate, soil properties) or biotic (e.g. inter- and intraspecific competition, prey availability). Some of these factors, such as leaf-litter volume or prey availability, may also vary seasonally. Also, the Ecuadorian Andes are known as being a hotspot of biodiversity for a large array of organisms, but it was not documented until now if this is also the case for ants.The general aim of the PhD project was to identify, by both descriptive and experimental approaches, the factors determining the structure of a ground-dwelling ant assemblage at a small-spatial scale and its temporal variation in an evergreen premontane tropical forest of the Ecuadorian Andes.In the descriptive part of the project, we studied both horizontal (along a transect) and vertical (across ground layers) species diversity and distribution of ground-dwelling ants. To attempt to explain the observed patterns, we measured a series of environmental factors varying at small spatial scale and/or seasonally: canopy openness, leaf-litter quantity, slope, and a series of soil physico-chemical properties (e.g. texture). The ant assemblage richness appeared to be at least as high as in the Amazonian Basin, with up to 33 species per m². The heterogeneity of species spatial distribution at small spatial scale was high, with distinct species composition (average Jaccard index = 0.2 ± 0.08 SD) and abundance (up to 40 fold) in contiguous plots. We observed a strong seasonal effect on the ant assemblage structure. The higher ant diversity and abundance found at the surface and in the mineral soil during the dry season suggested a seasonal peak of activity on the ground surface and the seasonal migration of drought-sensitive species downwards in the soil. Ant diversity was related to distinct environmental factors according to the ground layer considered. We found strong correlations between litter amount and dominant ant distribution in the leaf-litter layer, while we found no correlation with any factor in the soil layer. The low amount of negative association between dominant species suggested a low interspecific competition.In the experimental part of the project, our aim was to identify experimentally the relative importance of habitat size vs. prey availability in structuring the leaf-litter ant assemblage. We studied the response of various ant trophic groups to an increased nutrient availability which boosted the decomposition of their leaf-litter habitat and enhanced the abundance of their prey. Bottom-up effect on the ant fauna (and other predaceous arthropods) regarding species composition and dominance was also studied. Stable isotope analysis was used to distinguish trophic groups among ants and mesofauna. Ants responded differentially according to their trophic group: despite increased prey availability, predatory species were negatively affected by nutrient supply, while other ant trophic group densities did not change. Our results showed that predatory ants are limited by habitat size rather than by prey availability, and that these ants are more affected by habitat loss than their prey, other ant trophic groups and other macrofauna taxa. Furthermore, a taxonomic shift occurred within each ant trophic group, leading to the replacement of dominant genera in fertilized plots.As a conclusion, our results emphasize the importance of distinguishing layers among the ground matrix, since both ant faunas and their response to environmental factors vary vertically and seasonally. The distribution of ground-dwelling ants was only weakly explained by both the environmental factors measured and by biotic interactions, at a small spatial scale. Also, our results emphasize the importance of distinguishing trophic groups among the ant assemblage, since the response of these groups under changing conditions was different. In this regard, stable isotope analysis was a useful tool for investigating the trophic ecology of various leaf-litter taxa, and it was successfully used for the first time to assess the diet of leaf-litter ants and their position in the Brown Food Web relative to other taxa. Also, the isotopic approach allowed us to increase the knowledge about the biology of a rare and cryptic ant species, by revealing its top-predatory position. The outstanding local species richness that we observed confirms that the Ecuadorian Andes are also a biodiversity hotspot for ants.Doctorat en Sciences agronomiques et ingénierie biologiqueinfo:eu-repo/semantics/nonPublishe

Using isotopic approach to study trophic relationships between ants and their prey: Proceedings du meeting Entomology in Belgium

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Using isotopic approach to study trophic relationships between ants and their prey

info:eu-repo/semantics/nonPublishe

Spatio-temporal variation in ant (Hymenoptera: Formicidae) communities in leaf-litter and soil layers in a premontane tropical forest

Nearly half of the ant species present in a tropical forest are directly in contact with the ground for nesting or foraging, with evidence of vertical stratification among ground layers (i.e. surface, litter, and soil). How ants in each layer respond to environmental factors and to seasonality remains little studied. We hypothesized that ant species distribution varied spatially and seasonally among the three ground layers and that their distribution was distinctly affected by various abiotic and biotic factors. Ants were collected in an Ecuadorian premontane tropical forest and their distribution was analyzed spatio-temporally: vertically (between the ground surface, leaf-litter, and mineral soil, using pitfalls, Winkler, and soil cores), horizontally (every meter along a 100 m transect) and seasonally (between the dry and the rainy seasons). Four environmental parameters were measured every meter along the transect: canopy openness, slope, leaf-litter depth, and leaf-litter volume. Correlations between species distribution, richness, abundance, and environmental variables were calculated. Species richness was high, with 176 species collected along the transect. Our results show a clear vertical stratification, with distinct faunal composition in each layer and a strong seasonal effect. Stable distribution of several dominant species between seasons suggests a low nest relocation rate. During the dry season, higher ant richness and abundance were found in pitfall traps suggesting higher activity on the surface of the forest floor. Similarly, higher ant richness and abundance found in the soil during the dry season suggest the migration of drought-sensitive species downwards deeper into the soil. Species richness and dominant species distribution were related to distinct factors according to the layer considered; we found strong correlations between the quantity of leaf-litter and dominant ant species distribution and species richness in the leaf-litter layer, while no correlation was found with any factor in the soil layer. Our results show that ant faunal composition and the response of ants to environmental factors vary vertically at small spatial scale and seasonally, which emphasizes the importance of distinguishing layers in the ground matrix.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Soil properties affect the small-scale distribution of subterranean ants in a montane tropical forest

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