Species in the carabid beetle genus Paussus (340 species) exhibit an extraordinary diversity of unique morphological structures, in part because they are obligate symbionts of ants (i.e., myrmecophiles). The taxonomy of Paussus is in a state of turmoil, as evinced by multiple contradictory classifications of the group. This is to some degree due to the striking phenotypic uniqueness of these beetles, which tends to obscure similarities that can be used to infer evolutionary relationships between species. The objectives of this project are to: (1) infer the evolutionary relationships within Paussus based on DNA sequence data; (2) examine the evolution of morphological characters using the resulting phylogenetic framework; (3) produce a novel species-group classification within Paussus and an electronic interactive key to those species groups; (4) produce a systematic revision of those species of Paussus endemic to Madagascar, one of the most diverse and threatened regions of the world; and, (5) provide georeferenced biodiversity data to environmental non-profit organizations and governmental agencies in Madagascar for science-based conservation planning. The phylogeny produced with this research will provide a stable evolutionary framework for the proposed systematic revision of the Malagasy fauna, as well as for all future revisions and biogeographic analyses within the genus. Analyses of character evolution will reveal patterns of evolution of some very unusual traits associated with myrmecophily. Distributional and life history data, species- and higher-level classifications, phylogenetic hypotheses, and paper and web-based identification tools will be made available to ecologists and conservation biologists as facilitated by Réseau de la Biodiversité de Madagascar (REBIOMA). Throughout this project, the PI will train high school students, undergraduates, and graduate students in morphological and molecular approaches to revisionary systematics research.