Phylogenetic trait conservation in the partner choice of a group of ectomycorrhizal trees

Ecological interactions are frequently conserved across evolutionary time. In the case of mutualisms, these conserved interactions may play a large role in structuring mutualist communities. We hypothesized that phylogenetic trait conservation could play a key role in determining patterns of association in the ectomycorrhizal symbiosis, a globally important trophic mutualism. We used the association between members of the pantropical plant tribe P isonieae and its fungal mutualist partners as a model system to test the prediction that P isonieae‐associating ectomycorrhizal fungi will be more closely related than expected by chance, reflecting a conserved trait. We tested this prediction using previously published and newly generated sequences in a B ayesian framework incorporating phylogenetic uncertainty. We report that phylogenetic trait conservation does exist in this association. We generated a five‐marker phylogeny of members of the P isonieae and used this phylogeny in a B ayesian relaxed molecular clock analysis. We established that the most recent common ancestors of P isonieae species and P isonieae‐associating fungi sharing phylogenetic conservation of their patterns of ectomycorrhizal association occurred no more recently than 14.2 Ma. We therefore suggest that phylogenetic trait conservation in the Pisonieae ectomycorrhizal mutualism association represents an inherited syndrome which has existed for at least 14 Myr.