DNA barcoding of bark and ambrosia beetles reveals excessive NUMT s and consistent east‐west divergence across P alearctic forests

A comprehensive DNA barcoding library is very useful for rapid identification and detection of invasive pest species. We tested the performance of species identification in the economically most damaging group of wood‐boring insects – the bark and ambrosia beetles – with particular focus on broad geographical sampling across the boreal Palearctic forests. Neighbour‐joining and B ayesian analyses of cytochrome oxidase I ( COI ) sequences from 151 species in 40 genera revealed high congruence between morphology‐based identification and sequence clusters. Inconsistencies with morphological identifications included the discovery of a likely cryptic N earctic species of D ryocoetes autographus , the possible hybrid origin of shared mitochondrial haplotypes in P ityophthorus micrographus and P . pityographus , and a possible paraphyletic X yleborinus saxeseni . The first record of O rthotomicus suturalis in N orth A merica was confirmed by DNA barcoding. The mitochondrial data also revealed consistent divergence across the P alearctic or H olarctic, confirmed in part by data from the large ribosomal subunit (28S). Some populations had considerable variation in the mitochondrial barcoding marker, but were invariant in the nuclear ribosomal marker. These findings must be viewed in light of the high number of nuclear insertions of mitochondrial DNA ( NUMT s) detected in eight bark beetle species, suggesting the possible presence of additional cryptic NUMT s. The occurrence of paralogous COI copies, hybridization or cryptic speciation demands a stronger focus on data quality assessment in the construction of DNA barcoding databases.