Lack of genetic differentiation after host range extension argues for the generalist nature of Pityogenes chalcographus (Curculionidae: Scolytinae)

The bark beetle, Pityogenes chalcographus, is one of the main pests in Picea abies stands, and it has also been found on other European Pinaceae species. With massive introductions of North American conifer species into European forests, this insect has extended its host range to exotic Pinaceae species. This study assessed whether a wider host range has influenced the genetic structure of P. chalcographus and has led to host specialization. Insects were collected from two different regions of France, where eight native and exotic conifer species coexist and were analyzed using mitochondrial and nuclear genetic markers. Considerable haplotypic diversity was observed within the regions and within host species from where P. chalcographus populations were collected. No genetic differentiation, especially with respect to host species associations, could be detected. Moreover, no relationship could be established between closely related P. chalcographus haplotypes and taxonomically related conifer species. The capacity of P. chalcographus for host shifting and dispersal may have played a key role in the rapid extension of its host range. These findings are important for pest management in forests and health and phytosanitary measures in the timber trade, especially for risk assessment in mixed coniferous forests including tree species of major economic importance