a—Mucoro- mycotina symbioses, are now needed. Acknowledgements M.i.B. and S.P. thank NERC for grants NEJI027193/1 and NE/ I025360/1. J.G.D. thanks the Leverhulme Trust for an Emeritus Fellowship. A Darwin Initiative Grant enabled S.P. and J.G.D. to collect fungal samples from Ascension Island. We thank Jim Trappe