Using wild individuals of 34 species of Asteraceae, we investigated the differences in five traits that are thought to affect the intensity of herbivory (concentrations of carbon, nitrogen, phosphorus, water, and total phenolics) between flower heads and leaves and the difference in combinations of those traits between flower heads and leaves. We also compared the phylogenetic relationship and trait similarity of the species and evaluated phylogenetic signals for each trait.

Flower heads had higher phosphorus and lower total phenolics than leaves. The traits we measured were more tightly inter-correlated in flower heads than in leaves. Moreover, the phylogenetic relationship did not match the similarity of the traits nor its combination among the species. This result may imply that selective force driving the adaptive convergences of flower head and leaf traits we observed are common and widespread in our study species.

In general, flowers are thought to have a higher fitness value than leaves. However, because our results showed that flowers have a lower concentration of total phenolics, this implies that the relative allocation of defensive compounds could not be explained solely by the fitness value of the organs. Perhaps plants employ an escape strategy rather than a defense strategy to cope with floral herbivores.