How many species is a species? Integrative taxonomy sheds light on the systematics of an insular beetle species complex comprised of 12 subspecies ( Coleoptera: Tenebrionidae : Konstantinos Ntatsopoulos, Emmanouil Meramveliotakis, Malda Stalimerou, Ioannis Anastasiou, Marcin Jan Kamiński, Anna Papadopoulou

Abstract

Complex diversification histories shaped by dynamic palaeogeographical processes, such as those associated with continental archipelagos, pose major challenges for delimiting taxonomic boundaries. The present study focuses on Dailognatha quadricollis , an insular group of darkling beetles with a complex taxonomic history that has presumably diversified non‐adaptively across the Aegean archipelago. For the first time, the taxonomic status of the 12 subspecies assigned to D. quadricollis is revised under an integrative framework, utilizing single nucleotide polymorphism (SNP) data obtained from double digest restriction‐site associated DNA (ddRAD) sequencing in combination with morphological characters and geographic information. Congruence among alternative species delimitation methods supports the subdivision of D. quadricollis into three species, resulting in the following taxonomic changes: Dailognatha quadricollis (Brullé) (= Tentyria laticollis Besser syn. nov .), Dailognatha carceli Solier stat. resurr . (= D. quadricollis anaphiana Koch syn. nov ., = D. quadricollis sporadica Koch syn. nov .), Dailognatha rugata Solier stat. resurr . (= D. obtusangula Reitter syn. nov ., = D. quadricollis montana Koch syn. nov ., = D. quadricollis plicata Koch syn. nov ., = D. quadricollis pseudobtusangula Koch syn. nov ., = D. quadricollis rhodica Koch syn. nov ., = D. quadricollis samosana Koch syn. nov .). A taxonomic key for the three delimited species is also provided, demonstrating the taxonomic utility of characters not previously studied within the group, including genital morphology and mesoventrite punctation. Overall, this study highlights the value of integrating genomic, morphological and geographical data when delimiting cryptic lineages across geographically fragmented systems and raises broader questions regarding the systematics of insular species complexes comprising multiple subspecies.