Fig. 2. Correlations between phenotypes measured in the field
and natural levels of resource availability. A. Average frond area
(mm2) as a function of local light availability. Each
point is the average of 10 individuals in each of 3 microsites to give a
single value of average frond area per site. Light availability is
measured as percent transmittance of photosynthetically active
radiation. B. Average root length (mm) as a function of water total
Phosphorus (µgL-1). Each point is the average of 10
individuals in each of 3 microsites to give a single value of average
root length per site.
Plants from the field were taken back to the lab and grown in a common
garden assay. Mean generation time in the common garden was 4.1 days
which resulted in a total of ~7 generations for the full
30-day common garden assay. Although diverse protists and cyanobacteria
were observed in the flasks with microscopy, their densities remained
low as the growth media never became green to the naked eye.
Whereas phenotypic variation in the field is due a mixture of
environmental and genetic sources, any persistent variation in the
common garden can be attributed to genetic differences. There was a
major reduction in phenotypic variation among sites, comparing
measurements from the field to those in the common garden, for both
frond area (Fig. 3 A&B), and root length (Fig. 3 C&D). Frond area
generally increased in the common garden compared to field measurements,
likely due to the vastly lower irradiance provided by artificial light
in the growth chambers (200 µmols/s/m2) compared to
natural irradiance, even in shaded sites.