Conclusions
Frond area and root length varied widely in the field and were
correlated with natural levels of resource availability, with plants
investing more biomass into the tissue responsible for the uptake of the
resource that is in short supply. This was most striking for root
length, for which variation among sites was more than sixfold, and
strongly correlated with levels of dissolved phosphorus. This large
phenotypic variation in the field was overwhelmingly a result of
phenotype plasticity, and not local adaptation. Despite the predominance
of environmental variation in both traits, there was also a genetic
basis to these traits that persisted when environmental variation was
removed. We recorded surprisingly high levels of genetic variation in
phenotype and fitness within sites, which itself indicates the presence
of strong purifying selection of about 1% per generation and the
potential to counter environmental change. Future work should focus on
uncovering mechanisms responsible for maintaining such high levels of
genetic variation in L. minor. The continued development ofLemnaceae as a model system in experimental population genetics
(Acosta et al. 2021), community ecology (Laird and Barks 2018) and
eco-evolutionary dynamics (Hart et al. 2019) promises illumination in
understanding the larger mechanisms responsible for maintaining
diversity more generally.
Acknowledgments: We thank Rachel Takasaki, 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.
Authors’ contributions: MDJ lead the field survey and performed
the common garden experiment. Analysis was done jointly by MDJ and GB.
The manuscript was written by MDJ. GB contributed substantially to
revisions. The study was conceived by GB with input from MDJ.
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.