AbstractMost major modern families of Hymenoptera were established in the Mesozoic, but the diversifications within ecologically key trophic guilds and lineages that significantly influence the character of modern terrestrial ecosystems – bees (Apiformes), ants (Formicidae), social Vespidae, parasitoids (Ichneumonidae), and phytophagous Tenthredinoidea – were previously known to occur mostly in the middle to late Eocene. We find these changes earlier, seen here in the early Eocene Okanagan Highlands fossil deposits of western North America. Some of these may have occurred even earlier, but have been obscured by taphonomic processes. We provide an overview of the Okanagan Highlands Hymenoptera to family level and in some cases below that, with a minimum of 25 named families and at least 30 when those tentatively assigned or distinct at family level, but not named are included. Some are poorly known as fossils (Trigonalidae, Siricidae, Peradeniidae, Monomachidae), and some represent the oldest confirmed occurrences (Trigonalidae, Pompilidae, Sphecidaesensu stricto, Peradeniidae, Monomachidae, and possibly Halictidae). Some taxa previously thought to be relictual or extinct by the end of the Cretaceous (Angarosphecidae, Archaeoscoliinae, some Diapriidae) are present and sometimes abundant in the early Eocene. Living relatives of some taxa are now present in different climate regimes or on different continents.
Early Eocene biotic and climatic change in interior western North America
