Molecular phylogeny reveals the gradual evolutionary transition to soft-bodiedness in click-beetles and identifies sub-Saharan Africa as a cradle of diversity for Drilini (Coleoptera: Elateridae)

Drilini are soft-bodied predatory click-beetles (Elateridae: Agrypninae) with incompletely metamorphosed females. Due to divergent morphology, their classification has been contentious. We present the first densely sampled molecular phylogeny of Drilini based on nuclear and mitochondrial markers. Altogether, 44 species, representing all genera, were analysed using maximum likelihood and the Bayesian approach. Molecular analyses recovered five major clades that were also well supported by morphology. Afrotropical lineages mark deep splits. Most Palearctic species belong to a terminal clade. A few species of the predominantly Afrotropical Selasia are distributed from Arabia up to the Himalayas and Thailand. The origin of Drilini is dated to the Late Eocene (similar to 35.5 Mya) and rapid radiation is identified from the Eocene/Oligocene to the Middle Miocene. We describe the gradual transformation of male morphological traits, e.g. the level of sclerotization, structure of mouthparts, loss of the thoracic interlocking mechanism, shortened elytra and expanded larviform abdomen. Five new genera, Austroselasia, Habeshaselasia, Illubaboria, Malacodrilus and Mashaselasia are proposed. Latoselasia, previously a subgenus of Wittmerselasia, is elevated to the genus rank. Five new species, Habeshaselasia nekemtensis, H. illubaborensis, Illubaboria bicolor, Malacodrilus hajeki and Mashaselasia aethiopica are described.