FERTILITY AND THE FOOD QUALITY OF WETLAND PLANTS - A TEST OF THE RESOURCE AVAILABILITY HYPOTHESIS

We tested the resource availability hypothesis of antiherbivore defence with emergent wetland plant species. A physiological measure of the food quality of these species was derived using the growth rates of Ostrinia nubilalis larvae on agar-based diets with plant secondary compounds and fiber incorporated at 20% of their concentration in fresh leaf tissue. The correlations between food quality and the weighted mean and median positions of these species along four different fertility gradients were examined. No correlations were found. Similarly, there was no correlation between food quality and the maximum relative growth rates of these plants as seedlings. These results and others in the literature point to the lack of generality in the food quality predictions made by optimal defence theory.