Statistical analysis
To test whether there were differences in phenotype among sites and
microsites in the field, we used a 2-way nested analysis of variance
(ANOVA) with microsite nested within site. Both site and microsite were
analysed as type II random factors. This was done for both response
variables (frond area and root length). Since the environmental
correlates were measured at the site level, all 30 measures of phenotype
(10 individuals x 3 microsites) were averaged to produce a single value
per site for frond area and root length. We then regressed site mean
phenotype (both frond area and root length) against the environmental
correlates (light availability, TN, TP, DN, DP, and pH) using linear
regression and simplified the models by removing non-significant terms.
To test whether there were differences in phenotype among sites and
microsites after the common garden assay we used a similar nested ANOVA
as that used for the field data, but with a 3rd level
(replicate flask), nested within microsite, using the 10 individuals per
flask as the error variance. Growth rate (fitness) was calculated for
each flask over the final 20 days of the common garden assay using the
standard formula for exponential growth\(r=\frac{\ln\left(\frac{\text{Nt}}{N0}\right)}{t}\) where
N0 is initial population size, t is time in days, and
Nt is population size at time t. To test for differences
in fitness among sites and microsites we used a similar nested ANOVA
with microsites nested within sites. However, since there is only a
single measure of fitness per flask, replicate flask was used as the
error variance.