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

Abstract

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 Pisonieae and its fungal mutualist partners as a model system to test the prediction that Pisonieae-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 Bayesian 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 Pisonieae and used this phylogeny in a Bayesian relaxed molecular clock analysis. We established that the most recent common ancestors of Pisonieae species and Pisonieae-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.

Two new endemic tree species from Puerto Rico: Pisonia horneae and Pisonia roqueae (Nyctaginaceae)

“…However, we still lack scientific studies exploring possible biotic or abiotic factors shaping these distributions. A possible explanation is the existence of species-specific interactions with ectomycorrhizal fungi, which can help species survive in particular abiotic conditions (Van der Putten et al 2010, Pickles et al 2015) and have been found to interact with Pisonia and other members of the Pisonieae clade for at least 14 Myr (Hayward and Horton 2014). We also lack molecular studies to infer the phylogenetic relationships and species divergence times among Caribbean Pisonia .…”

Plant community responses to stand‐level nutrient fertilization in a secondary tropical dry forest

“…The distribution of species and plant functional groups at Horizontes is similar to that observed across nearby regenerating forests in northwestern Costa Rica (Powers and Tiffin ). The majority of trees are deciduous and arbuscular mycorrhizal, although eight species are evergreen and one of these is known to associate with ectomycorrhizal fungi ( Pisonia aculeata , Hayward and Horton ).…”

New evidence of ectomycorrhizal fungi in the Hawaiian Islands associated with the endemic host Pisonia sandwicensis (Nyctaginaceae)

“…To place P. sandwicensis, P. umbellifera and P. brunoniana phylogenetically, we re-analyzed a set of chloroplast and nuclear sequences from Pisonieae members we have previously generated (Hayward and Horton, 2014). These sequences represent five markers from 14 Pisonieae species, including the three studied here, and are available under GenBank accession numbers JX644435eJX644437, JX844233eJX844290 and KJ522684eKJ522688 (see Hayward and Horton, 2014 for details).…”

“…These sequences represent five markers from 14 Pisonieae species, including the three studied here, and are available under GenBank accession numbers JX644435eJX644437, JX844233eJX844290 and KJ522684eKJ522688 (see Hayward and Horton, 2014 for details). BEAST 1.7.5 (Drummond et al, 2012) was used to generate phylogenies for plants and for fungi.…”

“…Therefore, within the context of the plant kingdom the EM symbiosis is a highly specialized interaction involving only a small percentage of all land plant families, and EM host plant species are often associated with specific fungi (Molina et al, 1992;Hayward and Horton 2014;Põlme et al, 2013). Carlquist (1974) suggested that organisms engaged in more specialized symbiotic interactions should be less common on isolated islands than in mainland communities.…”