Molecular phylogeny of Pompilinae (Hymenoptera: Pompilidae): Evidence for rapid diversification and host shifts in spider wasps

Pompilinae are one of the largest groups of spider wasps. Their phylogeny has never been studied with molecular data. Most pompilines are generalist at the spider host family level, but there is some specificity at the ecological level (i. e. host guild). We aimed to test the monophyly of Pompilinae tribes and genera. We also aimed to test whether changes over time in the rate of diversification are associated with host shifts. The first molecular phylogenetic analysis concentrating on Pompilinae spider wasps is presented based on the analysis of five nuclear loci (28S, EF1, LWRh, Wg, Pol2) for 77 taxa in 36 genera. Data were analyzed using maximum likelihood (ML) and Bayesian inference (BI) phylogenetic frameworks. The phylogenetic results were compared with previous hypotheses of tribal classification and generic relationships in the subfamily. The classification of Pompilus and Agenioideus was also discussed. A Bayesian relaxed molecular clock analysis was used to examine divergence times. Ancestral host family and host guild were reconstructed using parsimony and ML methods. Diversification rate-shifts were tested taking into account taxon sampling bias using ML and BI approaches. None of the tribes proposed by previous authors are monophyletic. Several genera (e.g., Pompilus, Microphadnus, Arachnospila, Schistonyx and Agenioideus) are not monophyletic. Divergence dating analyses produced a well-supported chronogram consistent with the BI and ML reconstructions. Ancestral host use reconstructions inferred the use of a guild of spider hunters (other hunters) as the ancestral state for Pompilinae; various switching events to other guilds occurred throughout the evolution of the group. The diversification of Pompilinae shows one main rate-shift that coincides with the use of ground hunters as hosts.