We compared the ant assemblages from four very heterogeneous habitats over a short-distance eleva... more We compared the ant assemblages from four very heterogeneous habitats over a short-distance elevational gradient of vegetation (due to the presence of an inselberg) at the Nouragues Research Station, French Guiana. We focused on litter-dwelling ants, combining the use of pitfall traps and the Winkler method according to the Ants of the Leaf Litter Protocol. This permitted us to note (1) a high leaf-litter ant diversity overall, (2) a decreasing diversity gradient from the lowland rainforest to the top of the inselberg, and (3) changes in species density, composition and functional structure. While the ant assemblages on the plateau and inselberg can be considered functionally similar and typical of an Amazonian rainforest, that of the transition forest, relatively homogenous, rather corresponded to an ant fauna typical of open areas. By contrast, the liana forest assemblage was unexpectedly rich and dense, sheltering a litter-dwelling ant fauna dominated by numerous and abundant cryptic species. These taxonomical and functional dissimilarities point out the great influence of the environmental heterogeneity, which, through variable abiotic conditions, contributes to maintaining an exceptionally rich ant biodiversity in these Neotropical habitats.
Brazil is one of the leading producers of soybeans and other annual crops, and in several regions... more Brazil is one of the leading producers of soybeans and other annual crops, and in several regions landowners are required by law to maintain 20 % of their lands with natural vegetation (i.e. as “legal reserves”). However, there is a growing concern that some of these reserves will be subject to increased levels of disturbance or even be lost as a result of the ongoing legislation reforms. In this sense, studies that evaluate the conservation potential of retaining natural habitats within agricultural areas are of great importance. We assessed the efficiency with which remnants of natural vegetation conserve the native ant fauna in a context of intensive agriculture. We compared the structure of ground-dwelling ant assemblages between crop fields and reserves located in different farms. Ant species richness was much higher in the reserves than in the crops, and this pattern was consistent in spite of variations in the type of crop planted in each field, and in the size (39–149 ha) and vegetation (open or closed savanna) of the reserves. From 41.4 to 76.4 % of all species recorded within each farm were exclusively found in the reserves. Differences in species composition were strong not only because the reserves had much more species, but also because the species that were present in both habitats showed contrasting patterns of abundance in each habitat. Overall, our results highlight that even small remnants of natural vegetation can have a significant potential to maintain a higher diversity of ants within an agriculturally dominated landscape.
Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hy... more Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hypertrophied trap-jaw mandibles, is characterized by a set of unexpected biological traits including colony size, aggressiveness, trophobiosis and hunting behavior. The size of one colony has been evaluated at ca. 952,000 individuals. Intra- and interspecific aggressiveness were tested and an equiprobable null model used to show how D. armigerum colonies react vis-à-vis other arboreal ant species with large colonies; it happens that D. armigerum can share trees with certain of these species. As they hunt by sight, workers occupy their hunting areas only during the daytime, but stay on chemical trails between nests at night so that the center of their home range is occupied 24 hours a day. Workers tend different Hemiptera taxa (i.e., Coccidae, Pseudococcidae, Membracidae and Aethalionidae). Through group-hunting, short-range recruitment and spread-eagling prey, workers can capture a wide range of prey (up to 94.12 times the mean weight of foraging workers).
Tatuidris kapasisp. nov. (Formicidae: Agroecomyrmecinae), the second known species of “armadillo ... more Tatuidris kapasisp. nov. (Formicidae: Agroecomyrmecinae), the second known species of “armadillo ant”, is described after a remarkable specimen collected in French Guiana. This species can be easily distinguished from Tatuidris tatusia by characters related to the shape of the mesosoma and petiole as well as to the pilosity, the sculpture, and the color.
To determine if a type of unicoloniality exists in the fire ant Solenopsis saevissima in its nati... more 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.Afin de déterminer si la fourmi de feu Solenopsis saevissima peut être unicoloniale dans son aire d’origine, nous avons effectué en Guyane française des tests d’agressivité intraspécifique. Nous avons identifié deux « entités coloniales » s’étendant respectivement sur 54 km et 12,5 km. Les ouvrières d’une même entité coloniale ne s’attaquent pas, mais sont agressives durant les confrontations « inter-entités ». La présence de ces « entités coloniales » s’étendant sur de vastes zones a des incidences agricoles et environnementales.
Insects, particularly ants, are good bioindicators of the state of ecosystems. Nevertheless, inco... more Insects, particularly ants, are good bioindicators of the state of ecosystems. Nevertheless, incorporating them into conservation surveys is expensive due to problems associated with their identification, which is exacerbated by the fact that there are fewer and fewer taxonomists working today. “Taxonomic sufficiency” (TS), which identifies organisms to a level of taxonomic resolution sufficient enough to satisfy the objectives of a study, has never been applied to Neotropical ant communities. We analysed five Neotropical datasets representing ant assemblages collected with different sampling methods in various habitats. We first treated them using two complementary and cumulative TS methods, higher-taxon and “indicator taxa” surrogacies, before testing a new approach called “mixed-level method” that combines the two previous approaches. For the higher-taxon surrogacy, we showed that, above species, genus is the most informative taxonomic level. Then, mixed-level method provided more information on ant assemblages than did the two others, even though the “indicator taxa” surrogacy was based on relevant indicator genera. Although habitat type has no effect on its efficiency, this new method is influenced by the dataset structure and the type of sampling method used to collect data. We have thus developed a new method for analyzing Neotropical ant faunas that enables the taxonomic work linked to the identification of problematic species to be significantly reduced, while conserving most of the information on the ant assemblage. This method should enhance the work of Neotropical entomologists not specialised in taxonomy, particularly those concerned with biological conservation and indication.
We examined the ecological impact of traditional land use by Wayana Amerindians in French Guiana ... more 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 degree 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).Nous avons examiné l'impact de l'utilisation traditionnelle de la terre par les Amérindiens Wayanas de Guyane Française en utilisant les fourmis comme bio-indicateurs. Ces fourmis ont été capturées grâce à une méthode d'échantillonnage rapide et les résultats analysés au moyen de cartes auto-organisatrices de Kohonen (SOM). Nous avons échantillonné : (1) le village Wayana ; (2) une plantation de manioc ; (3) une plantation abandonnée depuis 6 ans ; (4) un fragment de forêt près du village ; (5) une ripisylve ; et (6) une forêt primaire. La diversité des fourmis décroît en fonction du degré de perturbation de l'habitat. Le SOM permet de suivre la succession écologique entre les six habitats. Le protocole utilisé est robuste car les mêmes conclusions sont atteintes après contrôle utilisant une information fragmentaire. Pour citer cet article : J.H.C. Delabie et al., C. R. Biologies 332 (2009).
Abstract. 1. Leaf-litter ants represent a major component of biodiversity and are excellent bioi... more Abstract. 1. Leaf-litter ants represent a major component of biodiversity and are excellent bioindicators reflecting the health of terrestrial ecosystems. This study, conducted in an unspoiled forest near the Nouragues Research Station, represents the first inventory of leaf-litter ant diversity conducted in French Guiana, and so can be considered as the baseline dataset for ants in this country.2. Ants were extracted from the leaf-litter using the Ants of the Leaf Litter Protocol, along an altitudinal gradient at four forest sites, including an inselberg.3. A total of 196 ant species representing 46 genera distributed over eight subfamilies were collected. Four distinct communities spread over a gradient of diversity were thus identified: the liana forest was the most species-rich (140 species) followed by the forested plateau (102 species), the transition forest (87 species) and the forest at the top of the inselberg (71 species).4. The discovery of species new to science plus several species recorded for the first time in French Guiana, coupled with the particular context of this area, suggests that the Nouragues Research Station might represent a centre of endemism. Once completed, this leaf-litter ant dataset will contribute greatly to the knowledge of ant biodiversity in French Guiana, and has the potential to progressively become an indispensable tool for country-wide conservation planning programmes.
This study aimed at showing the applicability of using a combination of four sampling methods (i.... more 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. To cite this article: S. Groc et al., C. R. Biologies 330 (2007).Le but de cette étude était de montrer l'applicabilité d'une combinaison de quatre méthodes d'échantillonnage (méthode Winkler, pièges pitfall, appâts et récolte manuelle) couramment utilisée sous les tropiques pour réaliser une étude de la diversité de fourmis en milieux tempérés. Nous avons récolté 33 espèces dans les Grands Causses, en comparant trois formations végétales : une pelouse steppique ( « causse » au sens strict), une chênaie et une pinède. Chaque technique n'est pas assez efficace à elle seule pour un échantillonnage acceptable ; en revanche, leur combinaison est recommandée, car elle permet de réaliser un inventaire plus complet des fourmis des milieux échantillonnés et d'étudier leur écologie. Pour citer cet article : S. Groc et al., C. R. Biologies 330 (2007).
We compared the ant assemblages from four very heterogeneous habitats over a short-distance eleva... more We compared the ant assemblages from four very heterogeneous habitats over a short-distance elevational gradient of vegetation (due to the presence of an inselberg) at the Nouragues Research Station, French Guiana. We focused on litter-dwelling ants, combining the use of pitfall traps and the Winkler method according to the Ants of the Leaf Litter Protocol. This permitted us to note (1) a high leaf-litter ant diversity overall, (2) a decreasing diversity gradient from the lowland rainforest to the top of the inselberg, and (3) changes in species density, composition and functional structure. While the ant assemblages on the plateau and inselberg can be considered functionally similar and typical of an Amazonian rainforest, that of the transition forest, relatively homogenous, rather corresponded to an ant fauna typical of open areas. By contrast, the liana forest assemblage was unexpectedly rich and dense, sheltering a litter-dwelling ant fauna dominated by numerous and abundant cryptic species. These taxonomical and functional dissimilarities point out the great influence of the environmental heterogeneity, which, through variable abiotic conditions, contributes to maintaining an exceptionally rich ant biodiversity in these Neotropical habitats.
Brazil is one of the leading producers of soybeans and other annual crops, and in several regions... more Brazil is one of the leading producers of soybeans and other annual crops, and in several regions landowners are required by law to maintain 20 % of their lands with natural vegetation (i.e. as “legal reserves”). However, there is a growing concern that some of these reserves will be subject to increased levels of disturbance or even be lost as a result of the ongoing legislation reforms. In this sense, studies that evaluate the conservation potential of retaining natural habitats within agricultural areas are of great importance. We assessed the efficiency with which remnants of natural vegetation conserve the native ant fauna in a context of intensive agriculture. We compared the structure of ground-dwelling ant assemblages between crop fields and reserves located in different farms. Ant species richness was much higher in the reserves than in the crops, and this pattern was consistent in spite of variations in the type of crop planted in each field, and in the size (39–149 ha) and vegetation (open or closed savanna) of the reserves. From 41.4 to 76.4 % of all species recorded within each farm were exclusively found in the reserves. Differences in species composition were strong not only because the reserves had much more species, but also because the species that were present in both habitats showed contrasting patterns of abundance in each habitat. Overall, our results highlight that even small remnants of natural vegetation can have a significant potential to maintain a higher diversity of ants within an agriculturally dominated landscape.
Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hy... more Here we show that Daceton armigerum, an arboreal myrmicine ant whose workers are equipped with hypertrophied trap-jaw mandibles, is characterized by a set of unexpected biological traits including colony size, aggressiveness, trophobiosis and hunting behavior. The size of one colony has been evaluated at ca. 952,000 individuals. Intra- and interspecific aggressiveness were tested and an equiprobable null model used to show how D. armigerum colonies react vis-à-vis other arboreal ant species with large colonies; it happens that D. armigerum can share trees with certain of these species. As they hunt by sight, workers occupy their hunting areas only during the daytime, but stay on chemical trails between nests at night so that the center of their home range is occupied 24 hours a day. Workers tend different Hemiptera taxa (i.e., Coccidae, Pseudococcidae, Membracidae and Aethalionidae). Through group-hunting, short-range recruitment and spread-eagling prey, workers can capture a wide range of prey (up to 94.12 times the mean weight of foraging workers).
Tatuidris kapasisp. nov. (Formicidae: Agroecomyrmecinae), the second known species of “armadillo ... more Tatuidris kapasisp. nov. (Formicidae: Agroecomyrmecinae), the second known species of “armadillo ant”, is described after a remarkable specimen collected in French Guiana. This species can be easily distinguished from Tatuidris tatusia by characters related to the shape of the mesosoma and petiole as well as to the pilosity, the sculpture, and the color.
To determine if a type of unicoloniality exists in the fire ant Solenopsis saevissima in its nati... more 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.Afin de déterminer si la fourmi de feu Solenopsis saevissima peut être unicoloniale dans son aire d’origine, nous avons effectué en Guyane française des tests d’agressivité intraspécifique. Nous avons identifié deux « entités coloniales » s’étendant respectivement sur 54 km et 12,5 km. Les ouvrières d’une même entité coloniale ne s’attaquent pas, mais sont agressives durant les confrontations « inter-entités ». La présence de ces « entités coloniales » s’étendant sur de vastes zones a des incidences agricoles et environnementales.
Insects, particularly ants, are good bioindicators of the state of ecosystems. Nevertheless, inco... more Insects, particularly ants, are good bioindicators of the state of ecosystems. Nevertheless, incorporating them into conservation surveys is expensive due to problems associated with their identification, which is exacerbated by the fact that there are fewer and fewer taxonomists working today. “Taxonomic sufficiency” (TS), which identifies organisms to a level of taxonomic resolution sufficient enough to satisfy the objectives of a study, has never been applied to Neotropical ant communities. We analysed five Neotropical datasets representing ant assemblages collected with different sampling methods in various habitats. We first treated them using two complementary and cumulative TS methods, higher-taxon and “indicator taxa” surrogacies, before testing a new approach called “mixed-level method” that combines the two previous approaches. For the higher-taxon surrogacy, we showed that, above species, genus is the most informative taxonomic level. Then, mixed-level method provided more information on ant assemblages than did the two others, even though the “indicator taxa” surrogacy was based on relevant indicator genera. Although habitat type has no effect on its efficiency, this new method is influenced by the dataset structure and the type of sampling method used to collect data. We have thus developed a new method for analyzing Neotropical ant faunas that enables the taxonomic work linked to the identification of problematic species to be significantly reduced, while conserving most of the information on the ant assemblage. This method should enhance the work of Neotropical entomologists not specialised in taxonomy, particularly those concerned with biological conservation and indication.
We examined the ecological impact of traditional land use by Wayana Amerindians in French Guiana ... more 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 degree 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).Nous avons examiné l'impact de l'utilisation traditionnelle de la terre par les Amérindiens Wayanas de Guyane Française en utilisant les fourmis comme bio-indicateurs. Ces fourmis ont été capturées grâce à une méthode d'échantillonnage rapide et les résultats analysés au moyen de cartes auto-organisatrices de Kohonen (SOM). Nous avons échantillonné : (1) le village Wayana ; (2) une plantation de manioc ; (3) une plantation abandonnée depuis 6 ans ; (4) un fragment de forêt près du village ; (5) une ripisylve ; et (6) une forêt primaire. La diversité des fourmis décroît en fonction du degré de perturbation de l'habitat. Le SOM permet de suivre la succession écologique entre les six habitats. Le protocole utilisé est robuste car les mêmes conclusions sont atteintes après contrôle utilisant une information fragmentaire. Pour citer cet article : J.H.C. Delabie et al., C. R. Biologies 332 (2009).
Abstract. 1. Leaf-litter ants represent a major component of biodiversity and are excellent bioi... more Abstract. 1. Leaf-litter ants represent a major component of biodiversity and are excellent bioindicators reflecting the health of terrestrial ecosystems. This study, conducted in an unspoiled forest near the Nouragues Research Station, represents the first inventory of leaf-litter ant diversity conducted in French Guiana, and so can be considered as the baseline dataset for ants in this country.2. Ants were extracted from the leaf-litter using the Ants of the Leaf Litter Protocol, along an altitudinal gradient at four forest sites, including an inselberg.3. A total of 196 ant species representing 46 genera distributed over eight subfamilies were collected. Four distinct communities spread over a gradient of diversity were thus identified: the liana forest was the most species-rich (140 species) followed by the forested plateau (102 species), the transition forest (87 species) and the forest at the top of the inselberg (71 species).4. The discovery of species new to science plus several species recorded for the first time in French Guiana, coupled with the particular context of this area, suggests that the Nouragues Research Station might represent a centre of endemism. Once completed, this leaf-litter ant dataset will contribute greatly to the knowledge of ant biodiversity in French Guiana, and has the potential to progressively become an indispensable tool for country-wide conservation planning programmes.
This study aimed at showing the applicability of using a combination of four sampling methods (i.... more 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. To cite this article: S. Groc et al., C. R. Biologies 330 (2007).Le but de cette étude était de montrer l'applicabilité d'une combinaison de quatre méthodes d'échantillonnage (méthode Winkler, pièges pitfall, appâts et récolte manuelle) couramment utilisée sous les tropiques pour réaliser une étude de la diversité de fourmis en milieux tempérés. Nous avons récolté 33 espèces dans les Grands Causses, en comparant trois formations végétales : une pelouse steppique ( « causse » au sens strict), une chênaie et une pinède. Chaque technique n'est pas assez efficace à elle seule pour un échantillonnage acceptable ; en revanche, leur combinaison est recommandée, car elle permet de réaliser un inventaire plus complet des fourmis des milieux échantillonnés et d'étudier leur écologie. Pour citer cet article : S. Groc et al., C. R. Biologies 330 (2007).
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