Tracing the evolution of Lathrobium: A phylogenomic approach using museum specimens.

Megadiverse insect lineages often lack robust phylogenetic frameworks, limiting our ability to understand the processes underlying their diversification and morphological evolution. The rove beetle genus Lathrobium (Staphylinidae: Paederinae), with nearly 800 described species distributed primarily across the Holarctic, exemplifies this challenge, exhibiting extensive morphological convergence and strong geographic structuring. We reconstructed the evolutionary history of Lathrobium using a phylogenomic dataset of ultraconserved elements (UCEs) obtained from both ethanol-preserved and historical museum specimens, complemented by mitochondrial cytochrome c oxidase subunit I (COI) data and fossil-calibrated divergence dating. The resulting phylogeny demonstrates that Lathrobium in a current sense is not monophyletic, with the genus Sinlathrobium nested within it and the subgenus Lathrobioma forming a deeply divergent lineage. Hind wings and eyes reduction evolved repeatedly across the phylogeny, consistent with convergent adaptation to montane and subterranean environments. Divergence time estimates indicate a Paleogene origin, with diversification shaped by climatic cooling and geographic fragmentation. Biogeographic analyses support a primarily Palearctic origin with multiple intercontinental dispersal events. These results provide a robust phylogenomic framework for Lathrobium and highlight the roles of dispersal limitation and ecological specialisation in shaping diversity in a widespread beetle lineage.