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

Abstract

Many scolytine beetle species have been expanding in new territories, travelling with wood and plants for planting, sometimes with a high impact on plant health. Here, we attempt to quantify the mobility of these species and to identify the biological drivers of mobility and impact. Mobility was estimated by counting the numbers of landmasses (contiguous pieces of land, surrounded by ocean or sea) colonised by each species. A series of potential drivers (taxonomic tribes; feeding regimes; polyphagy; reproductive strategy; host taxa; aggregation pheromones and long-range primary attractants), as well as impact on host health were recorded. A total of 163 species were identified, out of 5546 counted in the whole subfamily. The cosmopolitan taxa amongst the subfamily showed significant disharmony with regards to invasion frequency. Four tribes (Xyleborini; Ipini; Crypturgini; Hylastini) were significantly over-represented and two others (Corthylini; Hexacolini) were under-represented. Some 53% of the 163 species are inbreeding, a very significant excess as compared to the whole subfamily (29%). The inbreeders colonised more landmasses than the outbreeders. There is a significant relationship between the number of host families attacked by a species and the number of colonised landmasses. Most of the invasive species are recorded to respond to long-range host primary attractants, only one quarter respond to pheromones. All very mobile species respond to long-range primary attractants and none is known to respond to pheromones. Very mobile species are all associated with a substantial or moderate impact. The most mobile species belong to a limited number of subtribes. They are often inbreeding, polyphagous and respond to long-range primary attractants, but do not produce pheromones. However, there are many counter-examples. The outbreeding Scolytus multistriatus attacks only three host families, producing aggregation pheromones and has established in thirteen landmasses, with a high impact. Due to these many exceptions, species-based risk prediction relying on the few traits routinely analysed in literature suffers from important uncertainties.

Preemergence mating, inbreeding, and their consequences in the bark beetle Ips typographus

“…Research has repeatedly highlighted that inbreeding is a characteristic seen in many exotic Scolytinae species (Jordal et al 2001;Grousset et al 2020;Lantschner et al 2020;Demidko et al 2021;Grégoire et al 2023). A review looking at 163 scolytines with invasion histories (SIHs: Scolytinae species with an invasion history) found that 53% engage regularly in inbreeding, compared to the 27% seen among all Scolytinae (Grégoire et al 2023). Some of these inbreeding species display mixed breeding-the possibility of mating with neighboring, non-related individuals when population densities are high.…”

DNA isolation in bark beetles: reliability of extraction methods and application in downstream molecular procedures

“…Several species within this group are widely acknowledged as significant agents of tree mortality in coniferous forests globally (Raffa et al 2008; Biedermann et al 2019). Additionally, they are inadvertently transported via wood products and wood packaging materials, and numerous species have effectively established worldwide, constituting a notable group of invasive forest insects (Lantschner et al 2020; Grégoire et al 2023).…”