Ancient fig wasps indicate at least 34 Myr of stasis in their mutualism with fig trees

Abstract

Fig wasps and fig trees are mutually dependent, with each of the 800 or so species of fig trees (Ficus, Moraceae) typically pollinated by a single species of fig wasp (Hymenoptera: Agaonidae). Molecular evidence suggests that the relationship existed over 65 Ma, during the Cretaceous. Here, we record the discovery of the oldest known fossil fig wasps, from England, dated at 34 Ma. They possess pollen pockets that contain fossil Ficus pollen. The length of their ovipositors indicates that their host trees had a dioecious breeding system. Confocal microscopy and scanning electron microscopy reveal that the fossil female fig wasps, and more recent species from Miocene Dominican amber, display the same suite of anatomical characters associated with fig entry and pollen-carrying as modern species. The pollen is also typical of modern Ficus. No innovations in the relationship are discernible for the last tens of millions of years.