The evolutionary history of mammoth wasps (Hymenoptera: Scoliidae)

Scoliid wasps comprise a clade of aculeates whose larvae are parasitoids of scarabaeid beetle grubs. While scoliids have been used as biological control agents, research into the group's evolution and the stability of scoliid taxonomy have been limited by a lack of reliable phylogenies. We use ultraconserved element (UCE) data under concatenation and the multispecies coalescent to infer a phylogeny of the Scoliidae. In order to mitigate potential issues arising from model misspecification, we perform data filtering experiments using posterior predictive checks. Our analyses confirm the position of Proscolia as sister to all other extant scoliids. We also find strong support for a sister group relationship between the campsomerine genus Colpa and the Scoliini, rendering the Campsomerini non-monophyletic. The Australasian genus Trisciloa is recovered as sister to the remaining members of the Campsomerini, excluding Colpa. Campsomeriella, Dielis, Megascolia, and Scolia are inferred to be non-monophyletic. Analyses incorporating fossil data indicate an Early Cretaceous origin of the crown Scoliidae, with the split between Scoliini+Colpa and Campsomerini sensu stricto most probably occurring in the Late Cretaceous. Posterior means of Scoliini+Colpa and Campsomerini s.s. crown ages are estimated to be in the Paleogene, though age 95% HPD intervals extend slightly back past the K-Pg boundary. Our estimates of the stem ages of Nearctic scoliid clades are consistent with dispersal across Beringia during the Oligocene or later Eocene. Our study provides a foundation for future research into scoliid evolution and biogeography by being the first to leverage genome-scale data and model-based methods.