Host specificity of insects in a community of three co‐dominant Eucalyptus species

In a subalpine association of three Eucalyptus species, phytophagous insects showed strong host preferences even among very closely related Eucalyptus species. Sixty‐three per cent of insect species attacked only one eucalypt species, 30% attacked two species and only 8% fed on all three. Ninety‐seven per cent of individuals belonged to species using one or two hosts. The results are discussed in relation to the degree of host specificity that might be expected when most potential hosts are members of a single genus, the way in which host specificity is determined, and the potential of insects with host preferences to affect the dynamics of plant communities.