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International audience; Crickets (Ensifera, Grylloidea) are not commonly used as ecological indicators in contrary to other Orthoptera (e.g., grasshoppers and katydids). However, they are sensitive to environmental changes and abundant in tropical regions. To evaluate whether crickets are relevant bioindicators of tropical ecosystems, we investigated cricket assemblages along a tropical ecological gradient. We collected crickets during both day and night in southern New Caledonia for three stages of ecological succession: open shrubland, preforest, and forest. Simultaneously, we measured several environmental variables, such as temperature and relative humidity, at each sampling site. Cricket species assemblages showed a clear response to ecological succession. The highest and lowest species richness and abundances of individuals were, respectively, found in forest and shrubland, with species specialized in each ecological stage revealing the conservation value of each of these stages. Similar results were found when considering only the part of cricket communities with the ability to acoustically communicate. This work is part of a larger research program about Neocaledonian crickets and contributes to support the use of acoustic approaches to monitor tropical environments. In conclusion, these findings highlight the potential value of crickets as an environmental indicator in tropical ecosystems. The results also contribute to the discussion of the intrinsic conservational value of shrublands in New Caledonia and similar ecotypes.; Bien que d’autres groupes d’orthoptères soient largement utilisés comme bioindicateur, les grillons sont peu considérés dans les études écologiques. Pourtant, les grillons sont à la fois sensibles aux changements environnementaux et très abondants dans les régions tropicales. Dans cette étude, nous avons décrit les assemblages de grillons le long d’un gradient écologique en milieu tropical. Nous avons collecté les individus en période nocturne et diurne, sur 12 sites, et dans trois formations végétales du Sud de la Nouvelle Calédonie : le maquis, le paraforestier et le forestier. Des variables environnementales comme la température et l’humidité relative ont été collectées simultanément aux relevés de grillons. Les assemblages de grillons montrent une réponse très claire à la succession environnementale, suivant le gradient écologique, avec une diversité d’espèce et une abondance d’individus plus élevées en milieu forestier qu’en milieu maquis. Chaque stade du gradient écologique montre un assemblage unique d’espèces. Des résultats similaires sont obtenus en ne considérant que la part de la communauté des grillons qui utilisent l’acoustique pour communiquer. Ces résultats, interprétés à la lumière de travaux complémentaires faisant parties du même programme de recherche sur les grillons de Nouvelle-Calédonie, supporte l’analyse de relevés acoustiques pour évaluer l’état des milieux. En conclusion, les résultats soutiennent l’intérêt des grillons comme indicateurs écologiques du milieu tropical. Ces résultats contribuent également à la reconnaissance de la valeur intrinsèque des maquis en terme de conservation de la biodiversité en Nouvelle-Calédonie et dans des écotypes similaires.

Insect diversity represents about 60% of the estimated million-and-a-half described eukaryotic species worldwide, yet comprehensive and well-resolved intra-ordinal phylogenies are still lacking for the majority of insect groups. This is the case especially for the most species-rich insect group, the beetles (Coleoptera), a group for which less than 4% of the known species have had their DNA sequenced. In this study, we reconstruct the first higher level phylogeny based on DNA sequence data for the species-rich darkling beetles, a family comprising at least 20 000 species. Although amongst all families of beetles Tenebrionidae ranks seventh in terms of species diversity, the lack of knowledge on the phylogeny and systematics of the group is such that its monophyly has been questioned (not to mention those of the subfamilies and tribes contained within it). We investigate the evolutionary history of Tenebrionidae using multiple phylogenetic inference methods (Bayesian inference, maximum likelihood and parsimony) to analyse a dataset consisting of eight gene fragments across 404 taxa (including 250 tenebrionid species). Although the resulting phylogenetic framework only encompasses a fraction of the known tenebrionid diversity, it provides important information on their systematics and evolution. Whatever the methods used, our results provide strong support for the monophyly of the family, and highlight the likely paraphyletic or polyphyletic nature of several important tenebrionid subfamilies and tribes, notably the polyphyletic subfamilies Diaperinae and Tenebrioninae that clearly require substantial revision in the future. Some interesting associations in several groups are also revealed by the phylogenetic analyses, such as the pairing of Aphtora Bates with Phrenapatinae. Furthermore this study advances our knowledge of the evolution of the group, providing novel insights into much-debated theories, such as the apparent relict distribution of the tribe Elenophorini.

Biological invasions are generally thought to occur after human aided migration to a new range. However, human activities prior to migration may also play a role. We studied here the evolutionary genetics of introduced populations of the invasive ant Wasmannia auropunctata at a worldwide scale. Using microsatellite markers, we reconstructed the main routes of introduction of the species. We found three main routes of introduction, each of them strongly associated to human history and trading routes. We also demonstrate the overwhelming occurrence of male and female clonality in introduced populations of W. auropunctata, and suggest that this particular reproduction system is under selection in human-modified habitats. Together with previous researches focused on native populations, our results suggest that invasive clonal populations may have evolved within human modified habitats in the native range, and spread further from there. The evolutionarily most parsimonious scenario for the emergence of invasive populations of the little fire ant might thus be a two-step process. The W. auropunctata case illustrates the central role of humans in biological change, not only due to changes in migration patterns, but also in selective pressures over species.

Correspondance: arnaud.estoup@supagro.inra.fr; International audience; Highly polymorphic genetic markers provide a useful tool for estimating genetic parametersin studies of the evolution of sociality in insects. We isolated and characterized 12 polymorphicmicrosatellite loci in the invasive ant, Wasmannia auropunctata, and described experimental conditions for PCR (polymerase chain reaction) multiplexing and simultaneously genotyping these loci in two sets of five and seven markers. The number of alleles per locus ranged from two to 14 and the observed heterozygosity ranged from 0.233 to 0.967. Moreover, results of cross-species amplification tests are reported in three other species of Wasmannia and in two species of the genus Allomerus

For the last 30 years, Wasmannia auropunctata (the little fire ant) has spread throughout the Pacific and represents a severe threat to fragile island habitats. This invader has often been described as a disturbance specialist. Here we present data on its spread in a dense native rainforest in New Caledonia. We monitored by pitfall trapping the litter ant fauna along an invasive gradient from the edge to the inner forest in July 1999 and March 2000. When W. auropunctata was present, the abundance and richness of native ants drops dramatically. In invaded plots, W. auropunctata represented more than 92% of all trapped ant fauna. Among the 23 native species described, only four cryptic species survived. Wasmannia auropunctata appears to be a highly competitive ant that dominates the litter by eliminating native ants. Mechanisms involved in this invasive success may include predation as well as competitive interactions (exploitation and interference). The invasive success of W. auropunctata is similar to that of other tramp ants and reinforces the idea of common evolutionary traits leading to higher competitiveness in a new environment.