Species richness of insect herbivore communities on Ficus in Papua New Guinea

Insect herbivores were sampled from the foliage of 15 species of Ficus (Mor aceae) in rainforest and coastal habitats in the Madang area, Papua New Gui nea. The collection included 13 193 individuals representing 349 species of leaf-chewing insects and 44 900 individuals representing 430 species of sa p-sucking insects. Despite a high sampling intensity, the species accumulat ion curve did not reach an asymptote. This pattern was attributed to the hi ghly aggregated distribution of insects on individual host trees. The numbe r of insect species collected on a particular Ficus species ranged from 34 to 129 for leaf-chewing and from 51 to 219 for sap-sucking insects. Two Fic us species growing on the seashore sustained less speciose insect communiti es than their counterparts growing in forest. For the forest figs, signific ant predictors of insect species richness included leaf palatability and le af production for leaf-chewing insects (40% of the variance explained), and tree density and leaf expansion for sap-sucking insects (75%). The high fa unal overlap among Ficus communities and the importance of local resources for insect herbivores suggest that highly specialized interactions between insect herbivores and Ficus in Papua New Guinea have not been conserved in evolutionary time. This is at variance with the dogma of old, extremely spe cialized and conservative interactions between insect herbivores and their hosts, providing numerous ecological niches in the floristically rich tropi cs. (C) 1999 The Linnean Society of London.