The superfamily Dryopoidea is a diverse group of beetles with a mixture of aquatic, semiaquatic, and terrestrial life histories. These beetles exhibit remarkable morphological diversity, particularly in the larval stages, which is likely associated with their repeated adaptation to aquatic habitats. The phylogenetic relationships among Dryopoidea families and subfamilies are controversial, as phylogenetic analyses based on morphology have failed to propose robust and consistent hypotheses. However, recent molecular phylogenetic studies have provided better resolution for the interfamilial relationships and suggested the non-monophyly of a few families. In this study, we conducted phylogenetic analyses of Dryopoidea obtained in Japan along with other groups in the Elateriformia (Byrrhoidea, Dascilloidea, Buprestoidea, and Elateroidea) using sequence data from ultraconserved elements with the maximum-likelihood method and species-tree analysis based on a multispecies coalescent model. Our results show that Dryopoidea is a monophyletic group, not sister to Byrrhoidea. In Dryopoidea, Dryopidae is sister to all other groups, and Psephenidae and Ptilodactylidae are not monophyletic groups. In Psephenidae, Eubrianacinae has clearly diverged from the other subfamilies (Psepheninae, Psephenoidinae, and Eubriinae) and is closely related to Callirhipidae; in Ptilodactylidae, Cladotominae is related to Psephenidae (except Eubrianacinae) + Chelonariidae and separated from the other Ptilodactylidae subfamilies (Anchytarsinae and Ptilodactylinae). Although ML analyses indicated paraphyly of subfamilies in Limnichidae and Psephenidae (except Eubrianacinae), this was resolved in species tree analysis. Our results show that Eubrianacinae and Cladotominae are clearly distinct groups with different origins from other subfamilies of the respective families and can be separated as independent families.

Graphical Abstract