The Richness, Abundance and Biomass of the Arthropod Communities on Trees

(1) The invertebrate fauna of six tree species in both Britain and South Africa was sampled using pyrethrum knockdown. Two of the tree species in Britain and three in South Africa were introduced; the rest were native. (2) Average faunal diversities were similar in South Africa and in Britain. (3) The South African arthropod community consisted of fewer, heavier individuals than the British ones and tended to have a more uniform, larger biomass overall. (4) Faunal diversity was similar for native and introduced trees for all guilds except the phytophages, which showed a lower diversity on introduced trees. (5) On every native tree, the most abundant species was an hemipteran; on four of the five introduced trees other orders provided the most abundant species. (6) Total species richness was correlated with tree abundance for both native and introduced trees in Britain. (7) Arthropod abundance increased with species richness-as communities became richer in species, they became more tightly packed. (8) The biomass and numbers of individual arthropods, classified by guild, was not clearly related to structural and other features of the individual trees sampled. (9) There was a positive correlation between the biomass of chewing phytophages and a measure of defoliation.