The elusive predisposition to mycoheterotrophy in Ericaceae

The rise and diversification of land plants was accompanied by mycorrhizal symbiosis, from their emergence to their adaptation to various biomes and ecological situations (Selosse et al., 2015). In most mycorrhizal associations, fungi provide soil minerals to the plant, in exchange for sugars derived fromphotosynthesis (Smith& Read, 2008; van der Heijden et al., 2015). However, several plant species adapted to shaded forest conditions by secondarily reversing this exchange of carbohydrates: they became achlorophyllous thanks to carbon provided by the fungus. This so-called mycoheterotrophic nutrition is described in over 400 species and evolved at least 40 times independently (Merckx, 2013), raising the question of what predispositions underlie these convergences.