Early wasp plucks the flower: disparate extant diversity of sawfly superfamilies (Hymenoptera: 'Symphyta') may reflect asynchronous switching to angiosperm hosts

The insect order Hymenoptera originated during the Permian nearly 300 million years ago. Ancestrally herbivorous hymenopteran lineages today make up the paraphyletic suborder 'Symphyta,' which encompasses circa 8200 species with very diverse host-plant associations. We used phylogeny-based statistical analyses to explore drivers of diversity dynamics within the 'Symphyta,' with a particular focus on the hypothesis that diversification of herbivorous insects has been driven by the explosive radiation of angiosperms during and after the Cretaceous. Our ancestral-state estimates reveal that the first symphytans fed on gymnosperms, and that shifts onto angiosperms and pteridophytes—and back—have occurred at different time intervals in different groups. Trait-dependent analyses indicate that average net diversification rates do not differ between symphytan lineages feeding on angiosperms, gymnosperms, or pteridophytes, but trait-independent models show that the highest diversification rates ...