An integrative revision of the subgenus Liophloeodes (Coleoptera: Curculionidae: Entiminae: Polydrusini): taxonomic, systematic, biogeographic and evolutionary insights.

The subgenus Liophloeus Weise, 1894 of Liophloeus Germar, 1817 (Coleoptera: Curculionidae: Entiminae: Polydrusini) consists of five morphologically similar species traditionally diagnosed based on the shape of the aedeagus. However, traits of the genital apparatus exhibit substantial and overlapping inter- and intraspecific variation. All five species have the same ecological requirements and occur in central and eastern Europe, mostly in montane areas. The focus of this work was to verify the taxonomic status and validity of Liophloeodes species using a combination of molecular and morphometric techniques. Specimens were collected from the entire distribution range and initially assigned to a species according to the aedeagal shape. Genetic diversity and phylogeny of the subgenus were studied using three molecular markers (two ribosomal, 28S-D2 and ITS2, and one mitochondrial, COI). Moreover, several morphological characters were used for multivariate morphometric analyses. Finally, presence and prevalence of bacterial endosymbionts among species were investigated. Phylogenies based on ribosomal markers suggest that traditional species are correctly delimited, whereas COI phylogeny suggests hybridization and introgression occurring between Liophloeodes species. Morphometric analyses confirmed low interspecific diversity. Two major bacterial endosymbionts, Rickettsia and Wolbachia, were detected in many populations. We argue that Liophloeodes consists of young lineages whose evolution and diversification was possibly mediated by cyclic climate change events.