A total-evidence approach resolves phylogenetic placement of ‘Cafius’ gigas, a unique recently extinct rove beetle from Lord Howe Island

Cafius gigas Lea, 1929 (Coleoptera: Staphylinidae) was a large rove beetle endemic to Lord Howe Island (LHI) resembling Cafius and the LHI flightless endemic Hesperus dolichoderes (Lea, 1925). Like several other LHI endemics, C. gigas became extinct due to human-introduced rats. It is a legacy species valuable for understanding the LHI biota in terms of evolutionary biology and historical biogeography. Whether C. gigas was a member of Cafius Curtis, 1829, restricted to oceanic shores and prone to trans-oceanic dispersal, or related to H. dolichoderes, would have different implications. We subjected C. gigas to a total-evidence phylogenetic analyses of morphological and molecular data using model-based and parsimony methods. As a result, it is transferred to Hesperus Fauvel, 1874 with the new combination Hesperus gigas (Lea, 1929) comb. nov. Our analysis indicates that the montane leaf litter inhabitant H. gigas evolved neither in situ nor from a seashore Cafius-ancestor, or from an ancestor shared by two other LHI endemic congeners, Hesperus pacificus Olliff, 1887 and H. dolichoderes. It also suggests that all three Hesperus species that currently occur on LHI could have evolved on various seamounts at various times before reaching LHI.