Colonization success of a tree-killing bark beetle: Geographic variation and mismatch with host preference

The preference-performance hypothesis (PPH) predicts that female insects maximize their fitness by ovipositing on hosts where their offspring perform the best. The preference-performance relationships in bark beetles are complex because before offspring development can occur in the phloem, adult bark beetles must first successfully invade host trees, and then construct galleries beneath the bark. Therefore, a positive correlation between host preference and successful colonization is necessary for the PPH in bark beetles to hold (i.e., the preference-colonization hypothesis in bark beetles). In this study, through field choice experiments, I investigated the successful colonization of the bark beetle, Polygraphus proximus, within four allopatrically distributed Abies species across a distinct biogeographic boundary in Japan. The results of this study showed that the biogeographic boundary did not limit the successful colonization by P. proximus. I observed that successful colonization was low in A. firma, despite it being an exotic species in the study sites and the most preferred at the study sites, indicating a mismatch between preference and colonization success. Additionally, I observed that A. sachalinensis had a high colonization success rate, even though it was the least preferred species at the study sites.