Arthropods in tropical oaks: differences in their spatial distributions within tree crowns

The arthropod activity in the upper and the lower zone of nine emergent oak trees (genus Quercus) of a submontane forest in Sabah, Borneo, Malaysia, w as investigated by using flight interception traps, yellow colour traps, an d arboreal pitfall traps. Number of arthropods did not differ significantly between the upper and the lower region of the tree crowns. Nevertheless, t he results reveal significant differences in the abundances of several arth ropod groups between the two zones. In the lower part of the oak crowns Hom optera and ants (mostly alates) were sampled in higher numbers, whereas the upper zone was dominated by Diptera and Hymenoptera (ants excluded). Beetl es and most other groups showed no significant differences in abundance bet ween the lower and upper zone of the oak trees. Thus, the arthropods of the investigated community are not evenly distributed. The arthropod community in tree crowns, which often has been treated as a homogenous unit, is in f act divided into subunits formed by differently composed arthropod assembla ges.