Predators can indirectly structure local plant communities by altering the diversity and behaviour of herbivores. These ‘trophic cascades’ can be seriously disrupted by the local extinction of top predators. They can also be restored by the subsequent re-introduction of top predators by conservationists. Here, we investigated trophic cascades involving kākā, puriri moths and their host trees. New Zealand kākā (Nestor meridionalis, Nestoridae) are large parrots that were extirpated from most of its range in the 20th century.
This study examined whether two species of lepidopteran larvae (Cleora scriptaria and Epiphyas postvittana) were deterred from feeding on the leaves of kawakawa (Macropiper excelsum) after the leaves had been damaged in three different ways: by larval feeding, using a hole punch or a metal rasp. A hierarchy of choice experiments was performed in the laboratory, examining the feeding 'preference' of these insects between undamaged or previously damaged tissue within the same leaf, between different leaves and between different plants.
The pattern of herbivore damage on the New Zealand pepper tree (kawakawa; Macropiper excelsum) caused by its main insect herbivore (Cleora scriptaria) was investigated in the field and laboratory. In the field, only a small proportion of kawakawa leaves had no herbivore damage and C. scriptaria typically produced a number of small holes in each leaf. Leaves were shed at a rapid rate but leaf shedding was not increased by higher levels of herbivore damage.
New Zealand flowers are frequently considered unspecialised allowing easy access to pollen and nectar by a wide range of visitors. Most conform with a syndrome of insect pollination (entomophily). Pollination of forest flowers by birds has been described for a range of species whose flowers are morphologically ornithophilous. On Kapiti Island and Little Barrier Island, all three species of New Zealand honeyeaters have been described feeding on flowers currently assumed to be entomophilous or where the pollination system is unknown.