COMPOSITION OF SPIDER COMMUNITIES IN THE CANOPIES OF RAIN-FOREST TREES IN BORNEO

Spiders from 10 rainforest tree canopies in Borneo were sampled by knockdown insecticide fogging. Spider density ranged from 2.0 to 10.1 m-2 on different trees, and species numbers ranged from 16 to 62; species diversity, as measured by William's alpha, ranged from 26 to 92. Similarity of the spider assemblages on individual trees was low, whether measured by the number of shared species or the Morisita-Horn index of similarity. The contribution of five descriptor variables of tree taxonomy and structure to the similarity of the spider assemblages on different trees was assessed using stepwise multiple regression. No variable made a significant contribution to the variation in similarity indices for the spider assemblages and it was concluded that either other factors were important in determining similarity or that the measurement of these variables was too imprecise. In particular, there was no evidence that taxonomic similarity between tree species influenced the similarity of spider assemblages. Results were compared with similar data from tropical and sub-tropical rainforests in Sulawesi and Australia. Species densities in Borneo and Sulawesi were similar but lower than in Australia. Species richness and diversity were markedly higher in the Bornean rainforest than in Sulawesi or Australia.