Assessing the role of leaf traits against herbivores and pathogens in Cnidoscolus (Euphorbiaceae)

Abstract

The role of some leaf characters (specific area, thickness, trichome density, water content and latex production) on the defence against insect herbivores and fungal pathogens was analyzed in three species of Cnidoscolus (Euphorbiaceae). Foliar damage was examined in adults of the tree species C. spinosus and C. megacanthus, and the herbaceous species C. urens, in populations located in the Biosphere Biological Reserve of Chamela-Cuixmala (Jal.) and in the Huatulco-Zimatán region (Oax.), Mexico. Seedlings of C. spinosus were also analysed. We assessed the following leaf traits: specific area, thickness, density of trichomes on both sides of the leaf, as well as latex and hydric content. In the three Cnidoscolus species, levels of damage caused by grazer insects were higher than the ones caused by pathogens. The lowest level of foliar damage was detected in C. spinosus, but the levels of damage in seedlings were higher than those in the adults. The two tree species showed higher levels of damage by grazers than the herbaceous species. We only detected a direct significant relation between leaf thickness and herbivory levels in seedlings of C. spinousus. No other significant relations were found. This study suggests that the assessed leaf characters do not seem to play a key role in defence of these three Cnidoscolus species.