Tree species preference and impact on native species community by the bark beetle Ips amitinus in a recently invaded region

Non-native bark beetle species represent a major threat to forest ecosystems. The bark beetle Ips amitinus has recently expanded its range from Finland into northern Sweden. In the present study, we asked the following questions: (i) What is the distribution status in Sweden? (ii) Is there a difference in preference and reproductive success between Norway spruce and Scots pine? (iii) How common is the species after range expansion and does it influence the native community of bark- and wood-boring beetle species? We established the presence of I. amitinus and co-existence with the native community through checks of logging residues at 382 localities in northern Sweden. In addition, attack densities and reproductive success were compared between spruce and pine through investigating field material and by a no-choice rearing experiment. We found that I. amitinus is distributed over large parts of northern Sweden. Within its distribution area, it was found in 58% of all checked localities. It is one of the most common bark beetle species in logging residues and a higher proportion of Norway spruce objects compared to Scots pine were colonised. Attack density and reproductive success were higher in Norway spruce in field material and in the rearing experiment. There was no significant difference in the number of native bark- and wood-boring beetle taxa between localities where I. amitinus was present or absent.