Abstract
Partner specificity is a well-known phenomenon in biotic interactions,
but little is known about biotic and abiotic factors that determine
specificity in plant-fungal associations. Using PacBio sequencing of
soils from monospecific and mixed forest stands, we determined the
predictors driving partner specificity in both ectomycorrhizal plants
and fungi. Fungal guilds differed strongly in the patterns of partner
preference and avoidance, and specificity to particular tree genera.
Specialist ectomycorrhizal fungi dominated in belowground communities,
and most species preferred one of their partner trees - mostly at the
plant genus level. Furthermore, all tree genera (sometimes species)
displayed preference towards certain fungal groups. Partner specificity
was unrelated to rarity of fungi or plants or environmental conditions
except soil pH. Depending on partner taxon, specificity in fungi tended
to increase with dominance and optimal pH of the partner tree genus and
stand age. Partner tree richness and increased evenness of
ectomycorrhizal fungi in multi-host communities promotes species
richness. However, mainly partner-generalist fungi contribute to the
high diversity in mixed forests. Our results further suggest that
reforestation with mixed tree species promotes soil biodiversity, and
that besides conserving mixed forests, protection of old pure stands may
be particularly important for conserving partner-specific
ectomycorrhizal fungi.