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Adaptation for oviposition into concealed cycad ovules in the cycad weevils Antliarhinus zamiae and A. signatus (Coleoptera: Curculionoidea)
- DONALDSON, JOHN S.
- Biological journal of the Linnean Society 1992 v.47 no.1 pp. 23-35
- Curculionidae, Encephalartos, evolution, gametophytes, host plants, larvae, oviposition, ovipositor, ovules, predation
- Antliarhinus zamiae (Thunberg) and A. signatus Gyllenhal are the only insects known in which the larvae feed exclusively on the cycad gametophyte. In their host plants, species of the cycad genus Encephalartos (Zamiaceae), the gametophyte is protected by a three-layered integument and substantial sporophyll tissues. Adaptation for oviposition into the gametophyte may, therefore, be crucial to this feeding specialization. Ovipositional behaviour and ovipositor structure in four species of Antliarhinus suggest that ovipositional traits suited to ovule predation preceded the evolution of this habit and that ovipositional traits in ancestral species provided the right environment for the evolution of ovule predation. Current ovipositional traits in A. zamiae and A. signatus probably represent responses to changes in cone structure after the evolution of ovule predation.