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.

This dataset is the result of a study investing the effect of Scots pine (Pinus sylvestris L.) defensive genotype, considered as the abundance of the terpene Δ³-carene, on the community composition of ectomycorrhizal fungi of seedlings.

The experiment was a fully-reciprocal transplant: six populations of Scots pine in Scotland were chosen (three from the west, three from the east), and seed from two maternal trees at each population was collected. One maternal tree at each site was known to have a low Δ³-carene abundance, and one was known to have a high Δ³-carene abundance. Seeds were germinated, and planted into three grids at each population. Each grid was 50cm x 50cm in total extent, with 5cm intervals. 3 - 5 seedlings per maternal family were planted in each grid at each site, resulting in a fully reciprocal cross.

At the end of the experiment, seedlings were harvested. The community composition of EM fungi on each seedling was characterised through morphotyping, counting the number of root tips of each morphotype on each seedling, as well as the number of non-mycorrhizal root tips. The identities of morphotypes were then confirmed through molecular barcoding with ITS. For a subset of seedlings from 4 growth sites, terpene profiles were generated from needle tissue using GCMS.

This allowed us to assess both the effect of maternal family and terpene character on the EM community composition of different seedlings across multiple sites, to investigate whether either variable affected association frequency with particular fungal species.

This dataset contains the full datasets used for the analysis, as well as scripts containing the code to run the models. For the MCMCglmm community turnover models,.Rdata files are also present containing the model runs reported in the manuscript. Please see README.txt for further information on the contents of each data file.