Host genetic variation in symbiosis filtering
Symbiosis filtering differences were significantly correlated with host
genetic distance (Fig. 3a). This correlation remained significant even
when spatial distance among alder individuals was corrected using a
partial Mantel test (r = 0.444, P < 0.001).
Furthermore, GDM analysis quantified the explanatory proportions of the
genetic distances of the hosts and other predictors, including spatial
distance among hosts, soil pH, amount of inorganic nitrogen in soils,
and community dissimilarity of Frankia in rhizosphere soils, for
symbiosis filtering differences (Fig. 3b). The genetic distance of
alders and other factors absolutely explained the 36.64% deviance in
the symbiosis filtering differences.
Where the deviance explained by the model with genetic distance and
other factors was 100 %, the genetic distance of alders uniquely
explained 47.94% of the deviance while the other factors uniquely
explained 1.31% (Fig. 3b). This result demonstrates that the host
genetic distance was the best of the measured predictors for symbiosis
filtering differences.
Taken together, our findings suggest that differences in symbiosis
filtering force among host individuals could generate slight differences
in symbiont composition among host individuals in order to alter members
of mutualistic bacteria obtained from rhizosphere soils, while symbiosis
filtering might work to preserve high homogeneity of symbiont
composition in host individuals. Moreover, the differences in symbiosis
filtering force were likely to covary with the genetic variation of host
plants rather than the soil environments surrounding the hosts.