Metapopulation dynamics of the coxella weevil (Hadramphus spinipennis) on the Chatham Islands SCIENCE FOR CONSERVATION 134

Katrin Schöps
A B S T R A C T The endangered monophagous coxella weevil, Hadramphus spinipennis, is confined to Mangere and Rangatira (South-East) Islands, Chatham Island group, New Zealand. This study was carried out on Mangere Island, where a metapopulation of weevils inhabits eleven distinct patches of their host plant, Aciphylla dieffenbachii. Local weevil population dynamics in one discrete patch of A. dieffenbachii were investigated using a capture-recapture method. Weevil numbers more than quadrupled
more » ... re than quadrupled during three consecutive summers, and survival and recruitment rates increased. Plant numbers halved over the same period. In the fourth summer the plant population died out and no weevils were found. Overexploitation by the weevils, particularly root feeding, was the probable cause of host plant death. In one local patch, over 90% of the weevils stayed within 06 m of where they were found during a 24-hour period. Weevils had a low tendency to leave a local patch.