Cosmopolitan Scolytinae: strong common drivers but too many singularities for accurate prediction

Abstract

AimMany scolytine beetle species have been expanding their range in new territories across geographic barriers, traveling with wood, wood products and plants for planting, sometimes with a high impact on plant health. Here we attempt to quantify the mobility of these cosmopolitan species and to identify the biological drivers of mobility and impact. LocationWorld Major taxa studiedColeoptera; Curculionidae; Scolytinae MethodsMobility was estimated by counting the numbers of landmasses (contiguous pieces of land, surrounded by ocean or sea) colonized by each species. A series of potential drivers (taxonomic tribes; feeding habits; polyphagy; reproductive strategy; host taxa; pheromones and primary attractants) as well as impact on host health were recorded. Results163 species were identified, out of 5546 counted in the whole subfamily. Four tribes (Xyleborini; Ipini; Crypturgini; Hylastini) were significantly over-represented, and two others (Corthylini; Hexacolini) were under-represented. 53% of the 163 species are inbreeding, a very significant excess as compared to the whole subfamily (29%). The inbreeders colonized more landmasses than the outbreeders. There is a significant relationship between the number of host families attacked by a species and the number of colonized landmasses. Species restricted to conifers colonized fewer landmasses than hardwood generalists. Species attacking both types of hosts are the most mobile. Most of the invasive species respond to host primary attractants, only one quarter respond to pheromones. All very mobile species respond to primary attractants, and none responds to pheromones. Very mobile species are all associated with a high or moderate impact. Main conclusionsThe most mobile species belong for a large part to a limited number of subtribes. They are often inbreeding, polyphagous and respond to primary attractants but do not produce pheromones. However, many species that do not, or only partly, belong to these categories, have established in several landmasses, sometimes with a high impact. For example, the outbreeding Scolytus multistriatus, that attacks only 3 host families and produces aggregation pheromones, has established in thirteen landmasses, with a high impact. Therefore, risk prediction needs to assess diversity of species-specific biological traits beyond the few routinely analyzed in literature.