Geographic structure of chemical variation in wild populations of thefuel crop Jatropha curcas L. in Mexico

Jatropha curcas L. (Euphorbiaceae)is a shrub that produces seeds with a high oil content that can be converted to biodiesel. Some studies have shown that this plant contains phytochemicals that cause adverse effects on herbivores; however, it is not known whether the phytochemical variation is geographically structured and, in turn, if it is associated with herbivory intensity. This knowledge would enable the selection of individuals with adequate chemical variation to decrease the herbivory of this plant. With this objective, total foliar content of saponins, trypsin inhibitors, phytic acids, and phenols were analyzed and herbivory quantified in eight wild populations of J. curcas in Chiapas, Michoacán, and Veracruz, Mexico. Using principal components analysis (PCA), the content of phenols, saponins, trypsin inhibitors, and phytic acids grouped individuals to their state or frequently to their population. A multiple linear regression model considering total phytochemical content, altitude and precipitation, explained herbivory intensity (multiple adjusted R2 = 0.62). The concentration of trypsin inhibitors (par. corr. = 0.51, P < 0.0001)and altitude (par. corr. = 0.769, P < 0.0001)were positively associated with herbivory, whereas the concentration of phytic acid (par. corr. = ?0.299, P < 0.019)and precipitation (par. corr. = ?0.503, P < 0.0001)were negatively associated. It can be concluded that phytochemical variation is structured geographically at the local level and that herbivory intensity is associated with the total phytochemical content, precipitation, and altitude.