Aim: Biodiversity is known to be unevenly distributed along latitudinal gradients. While this pattern has been observed for many different organisms, it is unclear whether the distributions of ecologically important belowground mutualists, such as orchid mycorrhizal fungi (OMF), also vary according to latitude. Location: Europe. Methods: We sampled 37 populations over a 3000 km latitudinal gradient of the European orchid Spiranthes spiralis to test whether the diversity and community composition of OMF are influenced by...