The data revealed a strong overall correlation between Platanthera orchid host genomic profiles and their root mycobiomes across populations in Denmark, indicating that genetically more similar individuals harbour more similar microbionts than more distantly related, in support of the hologenome theory. Further, the project found significant correlation between orchid mycobiomes and specific soil variables in their habitats, especially between certain fungal strains and highly calcareous soils, indicating a role of the mycobiome in adaptation to local conditions by the host plant.
The assessment of microbiome range and variability of microbiome in 28 Platanthera species in eastern US demonstrated that composition and variability in microbiome differ among orchid species, confirming an effect of the host plant species on its microbiome. Both generalist and specialists Platanthera orchids were characterised, with specialists associating with 1-few mycobionts across their distribution area, while generalists associated with a broader range of mycorrhizal fungi. Closely related species had more similar mycobiont profiles, whereas more distantly related taxa were less likely to have an overlap in mycobionts. For most Platanthera taxa, we did not find any correlation between geographic distance between populations within taxa, and their mycobionts. However, in several species, mycobiont composition was correlated with intraspecific genetic clustering and biome type. These taxa exhibited substantial intraspecific genetic differentiation, with distinct coastal, mountain, and inland populations, which were associated with different mycobiont partners. This pattern indicates that plant mycobiont composition varies across habitat types and could be involved in local adaptation.
