Influence of leaf traits on the spatial distribution of arboreal arthropods within an overstorey rainforest tree

Abstract

Abstract. Several attributes of foliage were measured from the Australian rainforest tree Argyrodendron actinophyllum Edlin (Sterculiaceae). These were related to estimates of abundance per leaf area of the most common arthropod guilds and families sampled with restricted canopy fogging. When all these arthropod groups were considered, much of the overall variance in arthropod spatial distribution could be attributed to leaf age characteristics, arthropod aggregation patterns, arthropod activity and distance to tree trunk. The fraction of variance which could be specifically explained by foliage attributes such as nitrogen‐, water‐ and fibre‐content, specific leaf weight, and epiphyll load was small for most arthropod groups (usually <30%). However, an index of food quality explained a higher proportion of variance (50%) in the abundance of phloem‐feeders. Leaf size and foliage compactness did not influence significantly the abundance of any arthropod group. Most herbivores were more abundant on young foliage than on mature leaves. With the exception of Corylophidae and Chrysomelidae, which were more abundant in the lower and upper canopy respectively, arthropod stratification was not conspicuous within the inner core of tree crowns. The results firstly emphasize the distribution of young foliage as a key factor affecting the abundance of many herbivores and, secondly, the importance of the local illumination regime for host leaf production and its indirect effects on the spatial distribution of arboreal arthropods.