Discussion
This study highlights how Frankia -host symbiotic communities are
shaped through spatial Frankia assembly and filtering forces in
nature. We comprehensively investigated genetic diversity and
composition of Frankia in different environments, using NGS. The
occurrence of host plant individuals promoted the local assemblage of
diverse Frankia strains and the greater ASV and OTU richness ofFrankia detected in rhizosphere soils around hosts compared to
root nodules and host-absent riparian soil. In addition, our results
suggest that the diverse Frankia community assemblies in
rhizosphere soils are affected by soil nitrogen. However, theFrankia composition in root nodules consisted of very few members
(Fig. 1). Because Frankia richness in root-nodules was
significantly lower than in the null model, our findings indicate that
members of symbionts within hosts were selected from surrounding pools
via filtering forces. The community dissimilarity approach suggests that
genetic variation in host plants underlies the symbiosis filtering
difference even though host genetics did not affect Frankiacompositions in nodules or the rhizosphere.