Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforest

1. Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce. 2. Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea. 3. A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80-92 species. 4. Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts. 5. In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae). 6. Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families.