Does host-plant exploitation influence the population dynamics of a rare weevil?
This paper provides evidence that an endangered monophagous weevil overexploits its host plant and can cause its local extinction. Over three consecutive summers a mark-recapture study was carried out on a geographically isolated weevil population on Mangere Island (New Zealand) to obtain population estimates and recruitment and survival rates. The host plants in the study area were mapped each summer. A release experiment was carried out to assess the host finding ability of the weevils and to simulate a local extinction of their host plants. At least 68% of the released weevils reached the host plants 100m away from the release site. During the three summers the weevil population more than quadrupled, while the area covered by the host plants halved. We predict the local extinction of the host plant population in the study area for the next summer and the migration of the weevils to other host plant patches.