Effects of abiotic environmental factors and host genetic variation on Frankia assembly
The dissimilarity of Frankia communities in root nodules was not associated with the genetic distance of hosts (r = −0.309,P = 0.903; Table 1). Community composition in symbionts is consistent across host individuals despite host genetic variation. Furthermore, the Frankia community dissimilarity in rhizosphere soils was also not associated with the host’s genetic distance (r= −0.137, P = 0.754; Table 1). However, the structure ofFrankia communities in rhizosphere soils was significantly affected by inorganic nitrogen in soils (R2 = 0.581, P = 0.017; Table 1), while there was no significant relationship between soil pH and Frankia communities (R2 = 0.212, P = 0.371; Table 1).