Herbivore Damage and Leaf Loss in the New Zealand Pepper Tree (‘kawakawa’; Macropiper Excelsum; Piperaceae)

New Zealand Journal of Ecology (1998) 22(2): 173-180 ©New Zealand Ecological Society suggested as a diagnostic feature of the plant (Beever, 1987). Although C. scriptaria feeds on some other host plants (Spiller and Wise, 1982) and kawakawa is host to a few other herbivore species (Spiller and Wise, 1982; Clare and Singh, 1988), kawakawa is the primary host plant of C. scriptaria larvae (Hudson, 1928) and this herbivore is its main grazer. This paper examines two processes by which the plant may lessen the effects of herbivore damage; leaf shedding and wound-induced chemical responses. Preliminary observations have indicated that kawakawa trees may shed leaves at a rapid rate. Although shedding leaves may reduce the photosynthetic capacity of the plant, shedding damaged leaves may be of an overall benefit by reducing levels of microbial infection and preventing depression of transpiration and photosynthesis in undamaged tissue (Grime, 1979; Addicott, 1982). The holes in kawakawa appear to have a ‘regular’ spatial pattern and may fit a model of herbivory based on wound-induced plant defences (Edwards and Wratten, 1982; Edwards et al., 1995). In these systems, it is hypothesized that herbivory induces the plant to produce antifeedant compounds which accumulate at the site of damage. The herbivore feeds until the concentration of these compounds becomes so high that the animal is forced to move away. This process produces a series of small, uniformly spaced, areas of damage such as those seen in the leaves of kawakawa. Introduction