The Impact of Destructive Insects on Reproduction in Six Species of Banksia L.f. (Proteaceae).

Abstract

Six species of Banksia (Proteaceae) were examined at two study sites near Perth for insect larvae that destroy flowers and seed. All species, B. attenuata, B grandis, B. ilicifolia, B. littoralis, B. menziesii and B. telmatiaea, showed some damage to the conflorescence (flowering spike) while all except B, grandis and B. ilicifolia had damage to the infructescence (fruit). Six lepidopteran larvae and a curculionid larva damaged conflorescences, and five lepidopteran larvae and three curculionid larvae consumed seed. The insects were found only on Banksia and were mostly host-specific. The insects prevent about one-third of conflorescences from developing seed, but only one-third of the total conflorescences develop into infructescences. It is not known why the remaining one-third of conflorescences do not set seed. Insects destroy up to 60% of the follicles, which contain one or two seeds, on these infructescences. Examples of possible adaptations of the conflorescence and infructescence for avoiding this insect damage are suggested.