Location, but not defensive genotype, determines ectomycorrhizal community composition in Scots pine ( Pinus sylvestris L.) seedlings

Jim Downie* (Corresponding Author), Andy F. S. Taylor, Glenn Iason, Ben Moore, Jonathan Silvertown, Stephen Cavers, Richard Ennos

*Corresponding author for this work

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For successful colonization of host roots, ectomycorrhizal (EM) fungi must overcome host defense systems, and defensive phenotypes have previously been shown to affect the community composition of EM fungi associated with hosts. Secondary metabolites, such as terpenes, form a core part of these defense systems, but it is not yet understood whether variation in these constitutive defenses can result in variation in the colonization of hosts by specific fungal species.

We planted seedlings from twelve maternal families of Scots pine (Pinus sylvestris) of known terpene genotype reciprocally in the field in each of six sites. After 3 months, we characterized the mycorrhizal fungal community of each seedling using a combination of morphological categorization and molecular barcoding, and assessed the terpene chemodiversity for a subset of the seedlings. We examined whether parental genotype or terpene chemodiversity affected the diversity or composition of a seedling's mycorrhizal community.

While we found that terpene chemodiversity was highly heritable, we found no evidence that parental defensive genotype or a seedling's terpene chemodiversity affected associations with EM fungi. Instead, we found that the location of seedlings, both within and among sites, was the only determinant of the diversity and makeup of EM communities.

These results show that while EM community composition varies within Scotland at both large and small scales, variation in constitutive defensive compounds does not determine the EM communities of closely cohabiting pine seedlings. Patchy distributions of EM fungi at small scales may render any genetic variation in associations with different species unrealizable in field conditions. The case for selection on traits mediating associations with specific fungal species may thus be overstated, at least in seedlings
Original languageEnglish
Pages (from-to)4826-4842
Number of pages17
JournalEcology and Evolution
Issue number9
Early online date27 Mar 2021
Publication statusPublished - 3 May 2021

Bibliographical note

JD was supported by a studentship from the School of Biological Sciences, University of Edinburgh. The authors would like to thank the landowners (LC: The Honourable PR Smith Trust, SD: Mr Hugh Tollemanche, BE: Scottish Natural Heritage, RM: Rothiemurchus Estate, AB: The RSPB, GD: Marr Lodge) for allowing access to conduct the necessary fieldwork, Joan Beaton for field assistance and production of seedlings, Sheila Reid for assistance in the field and chemical analyses, David Sim for assistance with fieldwork, Wendela Tarbuck who conducted some of the morphotyping, Nadine Thomas, Will Goodall‐Copestake, and Annika Perry for their help, training, and advice on the molecular portion of this work, and Ally Philimore and Jarrod Hadfield (University of Edinburgh) for their help constructing the turnover models. The authors also thank Scottish Government Rural and Environment Science and Analytical Services (RESAS) for funding and the two anonymous reviewers whose comments were very helpful in improving the manuscript.


  • community composition
  • ectomycorrhizal fungi
  • evolution
  • mutualism
  • Scots pine (Pinus sylvestris)
  • secondary metabolites


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