DNA barcoding in Dorcadionini (Coleoptera, Cerambycidae) uncovers mitochondrial-morphological discordance and the hybridogenic origin of several subspecies

Dorcadionini is a highly speciose tribe within Cerambycidae and is also one of the most challenging in terms of species identification owing to the large number of taxa, intraspecific variability or similarity between species. To support species identification and taxonomic decisions, we generated DNA barcodes for 24 species and 152 specimens. Cases of disagreement between the barcode and taxonomic species were further analysed with the 28S and internal transcribed spacer 2 (ITS2) nuclear markers. The mitochondrial variation is mostly in accordance with the traditional taxonomy except a case of haplotype sharing between Dorcadion murrayi , Dorcadion axillare and Dorcadion pusillum that suggest hybridisation events. We hypothesise that introgression is the likely explanation for part of the large morphological variability found in many other species. In Dorcadion aethiops and Dorcadion fulvum , the taxonomic subspecies are not distinguishable using molecular data, as the haplotypes are identical or very similar, while in Dorcadion equestre , the subspecific structure is in accordance with the genetic data. A low between-species divergence ranging from 0.62 to 2.38% was found in four species, in contrast with the deep intraspecific divergences in D. equestre . We use two methods for single-locus species delimitation (General Mixed Yule Coalescent and Poisson Tree Processes), but none was perfect as both have shortcomings in oversplitting or lumping species. Dorcadion fulvum fulvum is confirmed for Romania.