Influence of leaf traits on the spatial distribution of insect herbivores associated with an overstorey rainforest tree.

Abstract

The spatial distribution of insect herbivores associated with the Australian rainforest treeArgyrodendron actinophyllum (Sterculiaceae) was investigated by restricted canopy fogging. The foliage of this species was low in nitrogen and water content, and high in fibre content. Herbivore abundance was positively correlated with the amount of young foliage present within the samples and in adjacent samples, and with the nitrogen content of young leaves. In particular, the occurrence of phloem-feeders was correlated with the magnitude of translocation within the samples. The influence of leaf water content upon herbivore distribution was marginal, presumably because this factor is not limiting in rain-forest environments during the wet season, which usually coincides with the season of leaf-flush. Specific leaf weight, leaf size and foliage compactness had little or no apparent effect on herbivore distribution. Since the magnitude of leaf turnover affected both the quantity and the quality, as exemplified by translocation effects, of young foliage available, this factor may be critical to herbivores associated with evergreen rainforest trees which are particularly low in foliar nutrients, such asA. actinophyllum.