Molecular phylogenetics of Elateriformia (Coleoptera): evolution of bioluminescence and neoteny

Phylogenetic relationships in the coleopteran Series Elateriformia (click beetles, jewel beetles, fireflies and allies) were investigated using > 3800 nucleotides of partial nuclear (small and large subunit rRNA genes) and mitochondrial (large subunit rRNA and cytochrome oxidase subunit I) gene sequences. The Elateriformia includes several soft‐bodied lineages, some of which retain larviform features in the adult stage (neoteny), and several major bioluminescent groups, including the families Lampyridae (fireflies), Phengodidae and Rhagophthalmidae whose relationships have been contentious. All recognized superfamilies (Elateroidea, Cantharoidea, Byrrhoidea, Buprestoidea, Dascilloidea, Scirtoidea) and 28 of the 37 families, represented in 112 individuals, were included in the analysis. Sequence alignment was based on static and dynamic homology assignments and partial removal of sequences of uncertain homology. Alignment variable regions caused a great deal of uncertainty but also contributed much of the phylogenetic signal that was insufficient to resolve deep relationships when these were removed. The main features of most analyses were the monophyly of Elateroidea + Cantharoidea (= Elateroidea sensu lato ), with Omethidae + Telegeusidae frequently occupying the basal node in this group; the affinities of Dascilloidea, Buprestoidea and a (broadly paraphyletic) Byrrhoidea, with unclear relationships among them; and the monophyly of Scirtoidea (including Decliniidae) as a rather distant outgroup to all others. When mapped on the resulting trees, soft‐bodied lineages were polyphyletic, contradicting the former Cantharoidea that had been united by this trait. Transitions to neoteny were either simultaneous with, or subsequent to, the origin of soft‐bodiedness in a minimum of seven lineages. The bioluminescent groups Lampyridae (including the enigmatic genus Drilaster ) and the tightly allied Phengodidae + Rhagophthalmidae were never monophyletic. The former showed close relationship to the species‐rich, soft‐bodied families Lycidae and Cantharidae, while the latter grouped with poorly resolved lineages at the base of Elateridae (click beetles). Hence, although key features as soft‐bodiedness, neoteny and bioluminescence in Coleoptera are largely confined to the Elateriformia, they appear to result from multiple origins, showing the propensity of closely related lineages to acquire similar features independently. © The Willi Hennig Society 2007.