Jeanne Kuahjek

Manaaki Whenua
Landcare Research,
P.O. Box 69,
Gerald St,
Lincoln 8152
Email: KuhajekJ@landcareresearch.co.nz

Despite their presence throughout most New Zealand forests, the impact of brushtail possums has been far from uniform. Variability in possum impact occurs within and between plant populations, communities and ecosystems. Within forest stands possum browsing is frequently concentrated on only a few trees that may be heavily defoliated or killed, while neighbouring individuals of the same species remain largely unaffected. In this project we are seeking to understand the basis for this variability.

Thus far, we have demonstrated significant differences in the palatability of individual trees of Meterosideros umbellata (southern rata) and Fuchsia excorticata (tree fuchsia). We have established that for both southern rata and fuchsia the chemical agent (antifeedant) that limits the amount of foliage a possum will consume is a water-soluble compound or group of compounds.

We are now working to determine whether differences in palatability amoung trees are heritable, or whether they are determined largely by the conditions under which the tree is growing. We are using AFLPs to assess heritability, coupled with field fertilizer trials to assess environmental influences on palatability. The investigation of heritability in the palatability of native trees to possums will give us a better idea of how possums are impacting native tree populations in New Zealand and potentially lend insite into minimizing these impacts.