We used a comparative approach to investigate heteroblasty in the Chatham Islands. Heteroblasty refers to abrupt changes in the morphology of leaves and shoots with plant height. Common on isolated islands such as New Caledonia and New Zealand, which once had flightless, browsing birds, heteroblasty is hypothesised to be an adaptation to deter bird browsing. The Chatham Islands are a small archipelago located 800 km off the east coast of New Zealand, which has clear floristic links to New Zealand.
The Noises and Motukawao Islands in Hauraki Gulf are small (maximum size 26 ha) and bush— clad, and none is permanently inhabited. Norway rats reached the Noises about 1956, but their history on the Motukawao group is unknown. Live and kill-trapping was carried out between August 1977 and December 1981, mainly on the Noises Islands. Trapping success was high initially but declined rapidly and remained very low after mid-1978. Rats travelled widely between consecutive captures in live-traps and three home ranges of males averaged 1.2 ha.
Provenance variation was studied in the growth and morphology of seedlings of silver beech (Nothofagus menziesii), red beech (N. fusca), hard beech (N. truncata), black beech (N. solandri: var. solandri:), and mountain beech (N. solandri: var. cliffortioides). Seedlings were grown for 2_ years in replicated provenance experiments at Rangiora and Rotorua.