Survivors crossed the K-Pg extinction line and radiated in the Quaternary: Phylogenetic genomics of the Cimbicidae
The Cimbicidae are the physically largest members of the Hymenoptera. They are herbivorous sawflies with clubbed antennae. The previous classification maintained that this family contains four subfamilies. Two of them, the Cimbicinae and Abiinae, are richly diverse and distributed across the Holarctic. The Corynidinae are confined to the Palaearctic realm and primarily diversified around the Mediterranean and southwestern Asia, while the most morphologically primitive Pachylostictinae has a restricted distribution in South America. However, the connotation of these subfamilies and phylogenetic relationships among genera is still confusing, which limits the study of their evolutionary history and hypotheses of their particular origin. Here, we used the nuclear single-copy genes and mitochondrial genomes to trace the evolutionary history of the Cimbicidae and combine an extensive molecular dataset with phylogenetically and stratigraphically constrained fossil calibrations to deduce an evolutionary timescale for the Cimbicidae. We reveal that the Cimbicidae survived the Cretaceous-Palaeogene (K-Pg) extinction. After then, the lineages differentiation and the diversification of the extant genera gradually initiated in the earlier half of the Paleogene. However, the rapid diversification of the Cimbicidae was almost completed in the later half of Paleogene and the earlier half of Neogene (4010 Myr.). This fast and almost simultaneous genus-level diversity of Cimbicidae underscores the significance of the boundary of geological historical sequence in shaping the taxonomic hierarchy of insects.