Past aridity and dust drove biodiversity crises and altered pollination in the ancient gymnosperm Ephedra (Gnetales)

The long-term effects of present-day climate change on pollination are unquantified. However, distinguishing climatic drivers of ancient changes in pollination could provide valuable insights into biotic responses to near-future climate states. Herein, we show that pollination in a group of gymnosperm shrubs (Ephedra L., Gnetales) was irrevocably altered by the Cenozoic expansion of drylands on two different continents. In Asia, increased continentality during the mid-Eocene drove aridification and strong, dust-carrying storms that promoted a shift to prevailing wind pollination in the core clade of Ephedra. Surface uplift in the North American interior together with global cooling caused the expansion of aeolian deposition and placed similar evolutionary pressures on ephedras there, beginning in the latest Eocene and continuing across the Eocene–Oligocene transition (EOT). These climatic changes fundamentally altered the abundance and evolution of this ancient plant lineage on both continents and determined pollination mechanisms in the core clade of Ephedra today. Based on fossil evidence, this review demonstrates how climate change may have major and permanent impacts on plant–pollinator networks, as well as demonstrates possible evolutionary consequences of near-future climate scenarios for which we have no modern analogue.