Potential host use by the Mediterranean pine engraver on novel tree species

Introduced species have the potential to cause great environmental damage, but many species introduced to an area will not have a large impact. It is critical that we develop the ability to predict which species will become damaging invaders, and manage ecosystems to minimize the probability that introduced species could establish. I present research results on the potential of the Mediterranean pine engraver, Orthotomicus erosus (Wollaston), to utilize North American tree species as hosts. I confirm that several North American conifers, species of pine and spruce, are suitable for the development of O. erosus. I then investigate the host acceptance behaviors of adults in contact with the outer bark. I show that differences among species occur during boring into the outer bark, and that beetles bore into both suitable and unsuitable tree species. The behavior of beetles before they are in contact with the bark was investigated with an olfactometer; odors from several conifer species do not affect the behavior of adult beetles. I also test the feeding response of beetles to extracts of bark and phloem chemicals. Several extracts contain feeding incitant or stimulant compounds, but the presence of these compounds in various tree species is different than adult bark boring behavior on those species. Finally, I used the data from my previous experiments and the phylogenetic distance among tree species in an attempt to predict the response of O. erosus to a second set of tree species from independent validation experiments. Phylogenetic distance from species with known beetle responses was not a good predictor of beetle response to novel plants. This body of work shows that O. erosus may accept a larger set of trees than are suitable for reproduction. Furthermore, adult host acceptance behavior is not determined solely by gustatory stimuli. Detailed knowledge about the stimuli governing host acceptance behavior is needed to predict the acceptability of new tree species to the beetle. The presence of acceptable but developmentaly unsuitable plants may determine whether species such as O. erosus are able to establish in a new environment.