Landscapes Drive the Dispersal of Monochamus Alternatus, Vector of the Pinewood Nematode, Revealed by Whole-Genome Resequencing

Pine wilt disease (PWD), Bursaphelenchus xylophilus, is an extremely threatening invasion forest disease throughout the world, especially in Asia. B. xylophilus is spread in Asia by vector beetles of Monochamus alternatus, which has long no effective control method. Understanding of landscape effects on the dispersal and outbreaks of forest pests is crucial to establishing effective ecological control strategies. Here, we analyzed the samples of M. alternatus collected in a fine-scale in order to estimate the effects of landscape types on the genetic structure and dispersal of M. alternatus. The landscapes included the geographical scales, forest types and land uses. The individuals of M. alternatus were genotyped by using whole-genome resequencing. Population genetic structures were clearly differentiated at the range of 250 kms, suggesting the intermediate scale is an effective barrier against natural dispersal of M. alternatus. We used the least-cost distances, least-cost transect analysis, and distance-based redundancy analysis to estimate the effects of forest types and land uses within the fine scales. The results showed that the gene flow and genetic diversity were positively correlated with host and mixed forests, whereas negatively with non-host forests. Among land-use landscapes, the roads had the positive effect on gene flow and genetic diversity but farmland and urban uses had negative effects. This highlights that humanmediated transport via roads was likely to be the main factor leading to the long-distance invasion of M. alternatus, whereas non-host landscapes could suppress the spread of this species. These findings may be useful to control the PWD dispersed by M. alternatus.