Pollination of Pyrrolizidine Alkaloid-containing Plants by Male Lepidoptera

Abstract

Certain plants containing pyrrolizidine alkaloids attract numerous Lepidoptera (Danainae, Ithomiinae, Ctenuchidae, Arctiidae) which congregate on dead shoots and inflorescences to feed. In many species, visitors are nearly all males. It is established that male Ithomiinae and Danainae ingest alkaloidal precursors for sex pheromones. Various parts of the live plants Heliotropium indicum L. and Eupatorium xestolepis Robinson are also attractive to these Lepidoptera and form the basis of an unusual relationship. H. indicum has a number of pollinators that visit the plant primarily for the purpose of obtaining pheromone precursors, spending much of their time at ripe seeds. In E. xestolepis , the floral fragrance may contain some of the volatile compounds typical of dead plant tissue which attract male Ithomiinae and Ctenuchidae. These insects constitute nearly 100% of the pollinators. In addition, this plant shows ecological specialization for subsisting in the habitat of its pollinators.