The Guild Composition of Arthropod Communities in Trees

Abstract

(1) Comparative knockdown samples of the invertebrate fauna in trees were taken during summer in South Africa and in Britain. Betula pendula, Quercus robur, Robinia pseudoacacia, Buddleia and Salix species were sampled in both countries; Erythrina caffra was sampled in South Africa only. (2) A total of 41 844 individuals were sorted and identified; only two of these were molluscs, the rest arthropods. (3) The composition of the arboreal guilds is analysed with respect to the numbers and proportions of families, species and individuals, and by biomass. (4) Taxonomic similarities in the arthropod faunas of trees are compared within and across countries. (5) The narrow-leaved flexible-stemmed, willows (Salix species) had a depauparate fauna and proportionately more phytophagous species than the broad-leaved trees sampled. (6) There was a striking uniformity in the proportion of predatory species recorded on all trees in both countries, and also a constant proportion of phytophagous species on different broad-leaved trees. The relative numbers of chewing and sap-sucking species were highly variable, but when summed resulted in proportionally uniform numbers of phytophagous species. These phenomena are discussed in the light of recent debate on patterns in community structure.