Challenges in Food-Web Restoration: An Assessment of the Restoration Requirements of a Honeydew-Gecko Trophic Interaction in the Auckland Region, New Zealand

摘要

Two geckos (Hoplodactylus duvaucelii and Hoplodactylus maculatus, Gekkonidae) have been recorded feeding on honeydew produced by the endemic scale insect Coelostomidia zealandica (Coelostomidiidae) on Korapuki Island, east of Coromandel Peninsula, New Zealand. Restoration projects underway on islands in the nearby Hauraki Gulf have reintroduced Hoplodactylus geckos, but to date little attention has been given to honeydew resources on these restored islands. We made observations on Korapuki Island (February 2008) that confirmed that ngaio (Myoporum laetum) and karo (Pittosporum crassifolium) were the most common host plants of C. zealandica, that heavy C. zealandica infestations occurred on both hosts, and that heavily infested hosts were regularly visited by insects and geckos. Hence, dense patches of C. zealandica honeydew may be a significant food resource for Hoplodactylus geckos. A survey for C. zealandica on Hauraki Gulf islands and the adjacent Auckland mainland (2006–2008) showed that dense C. zealandica infestations were entirely missing from the Auckland region. Ngaio was sparse at the survey sites and none carried C. zealandica, whereas karo was locally abundant, but was never heavily infested by C. zealandica. Introduced non-native animals and habitat loss have affected the distribution of Hoplodactylus geckos and may also have affected the distribution of C. zealandica and its host plants. As a result, the distinctive trophic interactions created by dense C. zealandica infestations are absent around Auckland, and the potential for restoration of consumer populations including geckos may be reduced.