Phylogeny, taxonomic revision, and the evolution of host associations in Grallatotermes-associated termitophilous beetles (Coleoptera: Staphylinidae: Aleocharinae)

Evolutionary transitions toward novel ecological niches are major drivers of biological diversification, yet in highly specialized symbiotic systems they may be constrained by strong evolutionary conservatism between symbionts and their hosts. Within the rove beetle tribe Corotocini (Coleoptera: Staphylinidae: Aleocharinae), the subtribe Termitogastrina is predominantly associated with termites of the genera Nasutitermes Dudley, 1890 and Trinervitermes Holmgren, 1912. An exception lineage comprises the physogastric genera Idioptochus Seevers, 1957, Leucoptochus Kistner, 1973, and Melanoptochus Kistner, 1973, which are exclusively associated with the termite Grallatotermes Holmgren, 1912 across East Africa. Despite their distinctive ecological specialization, the phylogenetic placement of these beetles has remained unresolved since their original descriptions. Here, a taxonomic revision and phylogenetic analysis of this assemblage are presented, based on a morphological matrix comprising 122 characters and 25 taxa. Maximum Parsimony, Maximum Likelihood, and Bayesian Inference analyses consistently recovered the three genera as monophyletic, with the association with Grallatotermes representing an ecological synapomorphy of the clade. Ancestral-state reconstructions indicate that the common ancestor of Termitogastrina was associated with wood-feeding, closed-foraging Nasutitermes -like termites, and that two major ecological transitions gave rise to morphologically distinctive lineages: one toward grass-feeding Trinervitermes and another toward lichen-feeding, open-foraging Grallatotermes . All species are redescribed and new records are provided. The independent occurrence of exclusive termitophile assemblages associated with lichen-feeding termites in Africa and the Neotropics suggests that host ecology may play an important role in shaping the diversification of termite-associated beetles.