ABSTRACT Investigating Damage, Genetic Correlations, and Natural Selection to Understand Multiple Plant Defenses in Passiflora incarnata

Plants commonly produce multiple, seemingly redundant defenses, but the reasons for this are poorly understood. The specificity of defenses to particular herbivores could drive investment in multiple defenses. Alternatively, genetic correlations between defenses could lead to their joint expression, even if possessing both defenses is non-adaptive. Plants may produce multiple defenses if putative resistance traits do not reduce damage, forcing plants to rely on tolerance of damage instead. Furthermore, resource shortages caused by herbivore damage could lead to compensatory changes in expression and selection on non-defense traits, such as floral traits. Natural selection could favor producing multiple defenses if synergism between defenses increases the benefits or decrease the costs of producing multiple defenses. Non-linear relationships between the costs and benefits of defense trait investment could also favor multiple defenses