Host plant influence on the mating success of male Mediterranean fruit flies: variable effects within and between individual plants

Observations of field-caged guava trees, Psidium guajava, revealed that males of the Mediterranean fruit fly (medfly), Ceratitis capitata, occasionally formed tight aggregations on the trunk and branches of certain trees. Males at these aggregation sites (stations) appeared to feed on the bark, and chemical analyses showed that stations contained high levels of the male attractant (alpha)-copaene whereas ‘nonstations’ on the same tree lacked this chemical. Previous work showed that male medflies exposed to pure (alpha)-copaene had a mating advantage over unexposed males. Here, we present data showing that the occurrence of stations is highly variable both within and between individual guava trees. Concurrent mating trials showed that male medflies exposed to entire guava trees containing stations or to individual stations for 3 h gained a mating advantage over unexposed males in tests conducted 1 or 3 days following exposure. In contrast, males exposed to entire trees lacking stations or only to nonstations on trees with stations had similar mating success as unexposed males. Additional experiments showed that exposure to guava leaves had no effect on male mating frequency but that exposure to fruits enhanced male mating success. The discussion considers potential mechanisms underlying the plant-induced increase in mating success and potential effects of (alpha)-copaene and other plant-borne compounds on the spacing of medfly leks in the environment.