Invertebrate species richness and density in relation to size of the New Zealand shrub Olearia bullata

Abstract

This study assessed the effects of host plant volume on invertebrate density and taxon richness on a native New Zealand shrub, Olearia bullata (Asteraceae). Specimens were collected by beating during a single summer/autumn sampling event from 30 O. bullata plants. The influence of the surrounding environment was also examined by assessing canopy connectivity between O. bullata shrubs and their nearest neighbours (O. bullata and other shrub species). Linear regression analyses suggested a positive association between invertebrate taxon richness and shrub volume, a relationship that was also apparent at the Order level for Coleoptera, Diptera, and Psocoptera. No significant results were found between shrub volume and invertebrate density at any taxonomic level. Negative associations were obtained between the density of Araneae and Hemiptera against the distance between O. bullata shrubs.