DNA barcode polymorphism within a common widespread rove beetle Quedius molochinus (Coleoptera: Staphylinidae)

Phylogenetic assessment of COI barcodes from 22 specimens identified as Q. molochinus based on external morphology and shape of the aedeagus revealed three non-sister clades within this recently revised species, with large molecular distance (6.3-7.8%) among them, suggesting their species status. On the contrary, preliminary study of the aedeagal internal sac (endophallus) of the available males from these clades and from the more numerous additional non-sequenced materials of Q. molochinus did not reveal notable variants. We report this case here because firstly, this goes against some cases observed in other beetles where endophallic characters may be the only morphological traits supporting molecular-based cryptic species, and secondly, these molecular clades are unexpected within a species we thought to be well-known. DNA barcoding, exploration of nuclear DNA markers and an in-depth examination of the fully everted endophallus for a wider sample of freshly collected specimens are required for further study and explanation of the detected molecular polymorphism of Q. molochinus. An illustration of the everted internal sac as a reference and new distributional data for this species are provided.