Host genotype shapes the foliar fungal microbiome of balsam poplar (Populus balsamifera)

Abstract

Foliar fungal communities of plants are diverse and ubiquitous. In grasses endophytes may increase host fitness; in trees, their ecological roles are poorly understood. We investigated whether the genotype of the host tree influences community structure of foliar fungi. We sampled leaves from genotyped balsam poplars from across the species' range, and applied 454 amplicon sequencing to characterize foliar fungal communities. At the time of the sampling the poplars had been growing in a common garden for two years. We found diverse fungal communities associated with the poplar leaves. Linear discriminant analysis and generalized linear models showed that host genotypes had a structuring effect on the composition of foliar fungal communities. The observed patterns may be explained by a filtering mechanism which allows the trees to selectively recruit fungal strains from the environment. Alternatively, host genotype-specific fungal communities may be present in the tree systemically, and persist in the host even after two clonal reproductions. Both scenarios are consistent with host tree adaptation to specific foliar fungal communities and suggest that there is a functional basis for the strong biotic interaction.

Figure 1. Distribution of balsam poplar.

The full natural range of balsam poplar is indicated with green shading . Circles mark the original sampling sites of trees, and stars mark the locations of common gardens (FBK = Fairbanks Garden, IH = Indian Head Garden). The ranges of the three subpopulations identified by Keller et al. are indicated with large ellipses.

Figure 2. Rarefaction curves of pooled 454 reads at 6 grammar thresholds.

Sequence-divergence based equivalents of grammar thresholds are shown in the figure. Dashed lines show 95% highest and lowest confidence intervals of rarefaction curves.

Figure 3. Species accumulation curve of assigned taxa.

Boxplots mark standard deviations. Gray shading represents confidence intervals.

Figure 4. Linear discriminant analysis of fungal communities.

A priori grouping of the LDA is based on host tree genotypes. Symbols on the plot represent the genotype group of the tree.