Phylogenomic relationships of bioluminescent elateroids define the ‘lampyroid’ clade with clicking Sinopyrophoridae as its earliest member

Bioluminescence has been hypothesized as aposematic signalling, intersexual communication and a predatory strategy, but origins and relationships among bioluminescent beetles have been contentious. We reconstruct the phylogeny of the bioluminescent elateroid beetles (i.e. Elateridae, Lampyridae, Phengodidae and Rhagophthalmidae), analysing genomic data of Sinopyrophorus Bi & Li, and in light of our phylogenetic results, we erect Sinopyrophoridae Bi & Li, stat.n. as a clicking elaterid‐like sister group of the soft‐bodied bioluminescent elateroid beetles, that is, Lampyridae, Phengodidae and Rhagophthalmidae. We suggest a single origin of bioluminescence for these four families, designated as the ‘lampyroid clade’, and examine the origins of bioluminescence in the terminal lineages of click beetles (Elateridae). The soft‐bodied bioluminescent lineages originated from the fully sclerotized elateroids as a derived clade with clicking Sinopyrophorus and Elateridae as their serial sister groups. This relationship indicates that the bioluminescent soft‐bodied elateroids are modified click beetles. We assume that bioluminescence was not present in the most recent common ancestor of Elateridae and the lampyroid clade and it evolved among this group with some delay, at the latest in the mid‐Cretaceous period, presumably in eastern Laurasia. The delimitation and internal structure of the elaterid‐lampyroid clade provides a phylogenetic framework for further studies on the genomic variation underlying the evolution of bioluminescence. Phylogenomic analyses define the ‘lampyroid clade’ with bioluminescent elaterid‐like Sinopyrophorus Bi & Li as a sister to soft‐bodied bioluminescent fireflies, glowworms and railroad worms (Lampyridae, Rhagophthalmidae, Phengodidae). The ‘lampyroid clade’ is a sister to click beetles (Elateridae), but the support for the monophyletic click beetles remains low. Fireflies and their non‐clicking relatives are modified click beetles. The first luminescent elateroid was a clicking beetle, with an estimated origin in the lower Cretaceous, putatively in Eastern Asia.