oa African Entomology - Systematics and evolution of the cycad-associated weevil genus Apinotropis Jordan (Coleoptera: Anthribidae)

Volume 7, Issue 1
  • ISSN : 1021-3589



Apinotropis Jordan is the only genus of the curculionoid family Anthribidae known to be exclusively associated with cycads, having been recorded only from certain species of Encephalartos in southern Africa. Recent surveys have produced the first records of these weevils from the Eastern Cape Province, South Africa, considerably extending the previously known range of the genus and the number of species. Three new species, A. brevis, A. robustus and A. nanus, are descriptionbed, and the two previously known species, A. verdoornae Jordan and A. oberprieleri Frieser, as well as the genus Apinotropis are redescriptionbed. These descriptionptions and redescriptionptions include several hitherto unused characters of the venter and male genitalia. In particulru; the males of all species possess ventral abdominal setiferous sex patches of a location and structure so far unrecorded in Anthribidae. The adelphotaxon of Apinotropis is uncertain but is likely to include the southern African genus Holophloeus Jordan. A phylogenetic analysis of the five known species of Apinotropis indicates a monophyletic origin and a strictly dichotomous branching sequence of these species. The immature stages and life history of Apinotropis are still unknown but, based on the examination of pupal chambers in cycad sporophylls and other biological details, a putative reconstruction of the life cycle is presented. Fungal cultures of the gut contents and frass pellets of A. oberprieleri, A. verdoornae and A. brevis yielded several saprotrophic hyphpmycetous fungi but no members of the wood-decaying Xylariaceae on which Anthribidae generally feed and develop. It therefore appears that Apinotropis is not mycetophagous but develops in cycad tissues, and that this lifestyle may represent the ancestral biological trait of the family (adapted only to a particular type of gymnosperm) rather than being a secondary specia1ization only in Apinotrorpis. The evolution of the genus is postulated to have been closely linked with that of the Encephalartos cycadifolius species group, including both cospeciation events and apparent secondary host shifts, and to have proceeded from an original development in trunk tissues to subsequent associations with female and later male cycad cones.

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