The Impact of Herbivory Pressure on Induction and Relaxation of Physical Defenses in Two Plants in an African Savannah

Abstract

Herbivory induced responses in plants have long been studied, but the way in which secondary variables, specifically growth rate and resource availability, affect these responses in the presence or absence of herbivores is still not well understood. The literature on this body of work suggests that in species of slower growth rates, as well as those in resource limited environments, a higher investment in defenses is favored. Studying the structural defenses in two plants of differing growth rates (Acacia etbaica and Solanum campylacanthum), this thesis examines the induction and relaxation of defenses across environments and treatments varying in levels of herbivory and resource availability, throughout a semi-arid African savannah. Results from this study show significant differences in defense levels with and across the two species, providing evidence for how differences in herbivory pressure and growth rate affect defenses in plants, and suggesting that herbivores are not the only factor in influencing how, and to what extent, a plant will defend itself.