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

1. For successful colonisation of host roots, ectomycorrhizal (EM) fungi must overcome host defence 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 defence systems, but it is not yet understood whether variation in these constitutive defences can result in variation in colonisation of hosts by specific fungal species.

2. 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 three months we characterised the mycorrhizal fungal community of each seedling using a combination of morphological categorisation 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.

3. While we found that terpene chemodiversity was highly heritable, we found no evidence that parental defensive genotypeor defensive phenoytpeaffected associations with EM fungi. Instead, we found that the location of seedlings, both within and between sites, was the only determinant of the diversity and makeup of EM communities.

4. These results suggest 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 unrealisable in field conditions. The case for selection on traits mediating associations with specific fungal species may thus be overstated, at least in seedlings.