Analysis of foliar monoterpenoid content in the California Bay Tree, Umbellularia calfironica, among populations across the distribution of the species

Abstract

Mature foliage of 110 trees from 11 populations of Umbellularia californica across its geographic range including diverse habitats were analyzed for monoterpenoid compositional variation by gas chromatography. Three previously unreported compounds for U. californica were identified: thujene, cis-sabinene hydrate, and trans-sabinene hydrate, however, all being minor components (<2.0% of the total composition). One-way ANOVA for each individual compound showed differing significant levels of variation among the 24 compounds analyzed, high ( P = 0.001 for 14 compounds, moderate (0.001< P<0.01) for umbellulone, and no significance for ( P<0.05) for seven compounds. Stepwise Discriminant Analysis of the variance in the entire data set reduced the number of variables to 15 (significance associated with Wilks' Lambda P<0.001). Canonical Discriminant Analysis by individual tree failed to completely separate any of the source populations. Average Linkage Cluster Analysis demonstrated that U. californica monoterpenoid composition apparently is genetically controlled with little significant geographic variation. Furthermore, the monoterpenoid compositional variation data did not support maintaining the subspecies designation for U. californica fresnensis Eastw. The lack of monoterpenoid variation among populations across a wide geographic distribution and diverse habitats enables generalization of results from studies of mammalian herbivory on U. californica.