Biological Constraints on Host-Range Expansion by the Wood-Boring Beetle Phoracantha semipunctata (Coleoptera: Cerambycidae)

Abstract

The eucalyptus longhorned borer, Phoracantha semipunctata F., is a cosmopolitan pest of Eucalyptus. The developing larvae damage trees by boring through the outer bark and along the cambium layer. Although the borer has become established in many parts of the world where it has encountered novel host-plant species, it has restricted its attacks to Eucalyptus and a few closely related species. The goal of this study was to investigate the behavioral and ecological barriers to host-range expansion by P. semipunctata. In laboratory experiments, gravid female P. semipunctata showed a low propensity to oviposit on logs of nine novel host species even though they had been deprived of their natural oviposition hosts. Survivorship of neonate larvae artificially introduced into logs of some novel host species was similar to that of larvae in Eucalyptus logs. However, larval development time in these novel hosts was greatly prolonged and adult body size was reduced. These findings suggest that oviposition behaviors of the adult beetles could restrict the host range of P. semipunctata to Eucalyptus species, and that oviposition preferences correspond well with performance of the larvae.