Instead of 300-million-year old twosome: Museomics reveals a synchronous diversification of Australian cycad-pollinating weevils (Coleoptera: Curculionidae) and cycads in the late Miocene

Cycads are palm-like gymnosperms, commonly known as “living fossils” due to their Permian origin, Mesozoic diversity and prolonged morphological stasis. Long thought to be wind-pollinated, it has been recently shown that insects, especially beetles, play major roles in cycad pollination. Given the old age of cycads, the obligate insect pollination is usually portrayed as a “300-million-year old twosome”, making for a good headline in the media. However, recent fossil-calibrated phylogeny indicated that all extant cycads derive from a global diversification in the Miocene. Furthermore, molecular dating of cycad-pollinating thrips has also shown their recent divergence in the late Miocene rather than an ancient origin. While it is now established that cycads are largely cantharophilous, the origin and divergence of their beetle pollinators remain unclear. Australia is one of the main centres of cycad diversity, and weevils have been shown to play significant roles in the pollination of Australian cycads. In this study, mitochondrial genomes were sequenced from museum specimens for phylogenetic reconstruction to investigate on the monophyly and systematic placement of Australian cycad-pollinating weevils, and divergence dating using fossil calibration was performed to estimate their origin. The results reveal that Australian cycad-pollinating weevils are a non-monophyletic group, with two different clades in two weevil subfamilies. The main radiation is indicated to have occurred from the late Miocene (ca. 14.1–3.4 mya), which is congruent with the diversification of Australian cycads (ca. 13–5 mya), thus further refuting any notion of an ancient (300-million-year-old) cantharophilous pollination of cycads in Australia.