Testing optimal defense theory in Solidago altissima

Abstract

<p>Optimal defense theory (OD) predicts that levels of plant defense should correlate with tissue value and risk of attack. That is, tissues of higher fitness value should be more heavily defended (Rhoades 1979). Other theories such as the growth-differentiation balance hypothesis (GDBH) predict that because of constraints and trade-offs associated with resource allocation, OD might not always hold (Herms & Mattson 1992). Depending on the type of defense measured neither theory may be supported (Barto & Cipollini 2005). We assessed the relative contribution of these two theories in a field common garden study of potted clones of the herbaceous perennial tall goldenrod, Solidago altissima (Asteraceae). We found that aspects of both theories accurately predicted defense levels, but that genotype described the most variation. These results may form the basis for a model of plant defense that focuses on life history traits.</p>