Abstract: 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. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract: Interspecific relationships among insects are often mediated by chemical cues, including non-volatile cuticular compounds. Most of these compounds are hydrocarbons that necessitate the use of solvents for their extraction, identification, and manipulation during behavioral assays. The toxicity of these solvents often precludes the removal and reapplication of hydrocarbons from and to live insects. As a consequence, dummies often are used in behavioral assays, but their passivity can bias the behavior of the responding insects. To overcome these limitations, we propose a method where cuticular compounds are extracted from live ants by placing them into glass vials half-filled with tepid water (ca. 34A degrees C) and vigorously shaking the vials to form an emulsion whose supernatant can be analyzed and/or reapplied to other ants. We demonstrate that cuticular compounds can be extracted from workers of the red fire ant, Solenopsis saevissima, and reapplied to the cuticle of workers from a sympatric species, Camponotus blandus (both Hymenoptera: Formicidae), while keeping the ants alive. Gas chromatographic-mass spectrometric analysis and behavioral assays were used to confirm the successful transfer of the behaviorally active compounds.

Abstract: Ripley’s K function is the classical tool to characterize the spatial structure of point patterns. It is widely used in vegetation studies. Testing its values against a null hypothesis usually relies on Monte-Carlo simulations since little is known about its distribution.
We introduce a statistical test against complete spatial randomness (CSR). The test returns the p-value to reject the null hypothesis of independence between point locations. It is more rigorous and faster than classical Monte-Carlo simulations. We show how to apply it to a tropical forest plot. The necessary R code is provided.

Abstract: Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant-plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant-myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca-Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees' fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree.

Abstract: 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. (C) 2011 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.