Hare. J. Daniel. 2002. Geographic and genetic variation in the leaf surface resin components of Mimulus aurantiacus from southern California. Biochemical Systematics and Ecology 30: 281-296.

Abstract: Nearly 30% of the dry weight of leaves of the chaparral subshrub Mimulus aurantiacus is comprised of leaf surface resins. This resin provides some defense against the insect herbivore, Euphydryas chalcedona and may also protect plants from desiccation and UV light injury. The resin is composed of several components and the different components may contribute differentially to the resin's multiple protective roles. The quantities of each of seven resin component from field-grown plants from six southern California populations of M. aurantiacus spanning a range of water availability and differing in attack by E. chalcedona, and clones from these plants grown in a common garden, were determined. Two predictions were tested: 1) E. chalcedona will attack plant populations with relatively low quantities of total resins and /or concentrations of the ortho dihydroxy resins, and 2) plant populations in drier environments will produce resin that is relatively richer in the methoxylated components than plant populations in more mesic environments. Although resin composition differed genetically among plant populations, the pattern of variation was not as predicted. Insect attack was not associated with lower levels of ortho dihydroxy compounds, and populations with higher proportions of methoxylated flavonoids were not found in the drier sites. The pattern of genetic variation among populations in resin composition therefore was not explained by the differences in chemical structure that were predicted to influence the role of the components as herbivore protectants or antidesiccants.