Conclusions
To return to our initial three questions we set out to address, we
conclude that the full L. minor microbiome unequivocally
supresses fitness of the host plant. This was the case in all
environment treatments for seven of the eight genotypes. The decrease in
fitness was accompanied by phenotypic changes, with plants producing
smaller fronds and shorter roots with the microbiome present. There was
some variation in the magnitude of the effect of microbiome on plant
fitness among genotypes perhaps because of differences in microbial
composition among sites. Likewise, there was variation among genotypes
in the phenotypic response to environment, but this was independent of
the microbiome. Although the microbiome clearly includes important
symbionts including several nitrogen fixers, it is a mistake to discount
the important pathogenic, parasitic, and competitive interactions, whose
influence seem to override that of mutualists.
Acknowledgments: We thank Julia Kossakowski, who helped with data
collection. This experiment was supported by a Discovery Grant from the
Natural Science and Engineering Research Council of Canada to GB and an
Alexander Graham Bell Canada Graduate Scholarship from the Natural
Science and Engineering Research Council of Canada to MDJ. SJVM was
supported by a grant from the Swiss National Science foundation.
Authors’ contributions: The study was conceived together by MDJ
and GB. MDJ and SVM performed the experiment. The manuscript was written
by MDJ. SVM and GB contributed substantially to revisions.
Competing interests: The authors declare no competing
interests.
Data availability: Raw data from which all figures were
generated will be stored in the Dryad repository before publication of
the article.