Do Lecythidaceae specialists (Coleoptera, Cerambycidae) shun fetid tree species?

Abstract

Characteristic secondary metabolites are currently acknowledged to play a pivotal role in the circumscription of a plant's insect fauna. A newly discovered association between wood-boring longicorn beetles (Cerambycidae) and their host trees belonging to the Brazil nut family (Lecythidaceae) inspired a yearlong rearing project in the lowland Neotropical rain forest of central French Guiana. Branches severed from five species of Lecythidaceae yielded 1813 cerambycids belonging to 37 species. Two of the five tree species, Couratari stellata and Gustavia hexapetala, yielded impoverished complements of cerambycids that included large percentages of generalists. Both tree species are characterized by fetid odors. Wood samples collected from the malodorous C. stellata, as well as from two well-colonized species, Lecythis poiteaui and Eschweilera coriacea, were analyzed for their volatile components. Sulfur compounds accounted for almost 15 percent of the volatiles detected from C. stellata, while they were at most minor components of the two well-colonized tree species. S-methylmethionine, isolated from a C. stellata wood sample, appeared to be the major sulfur compound contributing to the distinctive smell. We hypothesize that this foul odor is a deterrent to specialist cerambycids seeking oviposition sites.