The evolution of arboreal carabid beetles

Abstract

The diversity of many groups of organisms is related to the evolution of features that contribute to rapid radiations. This project reconstructed the phylogeny of carabid beetles in the subfamily Harpalinae, a speciose group of terrestrial predators. The phylogenetic inference focused on the sister group relationships, the monophyly of the subfamily and the tribal relationships within harpalines. Molecular sequence data, primarily from 28S ribosomal DNA and the wingless gene, were collected from more than 200 carabid beetles. Parsimony, minimum evolution distance, maximum likelihood, and Bayesian phylogenetic analysis methods were used to reconstruct the phylogeny of harpalines. Brachinine bombardier beetles and austral psydrines were found to be closely related to the harpaline clade. Within harpalines, zuphiites formed a clear clade as did pseudomorphines + graphipterines + orthogoniines. However the lebiomorph assemblage and the tribe Lebiini were not monophyletic. With the use of harpaline phylogenetic hypotheses, the evolution of the arboreal lifestyle was elucidated within the subfamily, including the rate and number of origins and losses of arboreality. Correlated evolution of several morphological characters and habitat was explored. Significant correlation of adhesive subtarsal setae and bilobed fourth tarsomeres on carabid legs were found with arboreality and may be arboreal adaptations, while long legs and long elytra are probably not associated with arboreality. The relationship of other morphological characters with arboreality is not clear. Harpalines may have been part of a rapid radiation of species diversity, where many lineages invaded new ecological niches and evolved novel morphological features to become adapted to their environment.