Figure 2. Correlations between constitutive or induced defenses
and herbivore pressure across 12 non-native plant species and 12 native
plant species. Relationships between the percentage of damaged leaf area
in the common garden experiment and constitutive defense assessed by
generalist Spodoptera littoralis larval weight gain on the leaves
of healthy plants (A) and assessed by phenolics (C) and triterpenoids
(E) contents in the leaves of healthy plants. Relationships between the
percentage of damaged leaf area in the common garden experiment and
induced defense assessed by difference in S. littoralis larval
weight gain on the leaves between healthy and damaged plants [-1 ×
(larval weight gain on the leaves of damaged plant – average of larval
weight gain on the leaves of healthy plant), B], and assessed by
differences in phenolics in the leaves between healthy and damaged
plants (content in the leaves of damaged plant – average of content in
the leaves of healthy plant, D) and difference in triterpenoids on the
leaves between healthy and damaged plants (content in the leaves of
damaged plant - average of content in the leaves of healthy plant, F).
Each point represents individual non-native species (red points) and
native congeners (blue points). Lines indicate significant linear
relationships. The embedding boxplots represents the comparison for each
group of species overall. * indicate p <0.05 and ***
indicate p <0.001.