Gastritis over Gastrisus Sharp (Coleoptera: Staphylinidae: Xanthopygina): Resolving a major taxonomic impediment with phylogenomics

With 334 species, the subtribe Xanthopygina forms a diverse and ecologically dominant component of the Neotropical beetle fauna, ranging from the southern United States south to Argentina. Species can be abundant in a variety of microhabitats and are frequently encountered in tropical forests. Although a number of morphologically distinct genera are now well defined and identifiable, the subtribe still suffers from several poorly defined genera with relatively generalized morphology. The worst of these is the genus Gastrisus Sharp, which has never had a morphological definition per se and has, over time, accumulated many morphologically disparate species. This nebulous concept of Gastrisus has further made it difficult to generically assign and describe new species. Here we assembled a phylogenomic dataset using anchored hybrid enrichment across a broad sample of Xanthopygina, including nearly all described genera, a representation of morphological variation within Gastrisus and a number of undescribed taxa we were unable to assign to a genus. Both maximum likelihood and coalescent analyses converged on a well resolved and stable topology for the subtribe, which will serve as a critical framework for continued taxonomic progress in Xanthopygina. Nine major lineages were identified, most congruent with previous work. The limits of Gastrisus were successfully identified, and the monophyletic core of the genus was recovered as sister to a redefined Nausicotus Sharp, which included Torobus syn. n. Several large species of Gastrisus were resolved as a clade of the Xanthopygus group and are here placed in Drepanagrios gen. n. An additional six new genera were discovered but will be described and treated in detail in future papers. In addition to Gastrisus, Phanolinus Sharp, Xenopygus Bernhauer, Phanolinopsis Scheerpeltz and Ocyolinus Sharp were recovered as paraphyletic, resulting in Elecatopselaphus syn. n. (=Phanolinus), the re-validation of Leptodiastemus Bernhauer stat. ressur. and the redefinition of Xenopygus, Phanolinopsis and Ocyolinus. We propose Phanolinus scheerpeltzi nom. n. as a replacement name for Phanolinus peruvianus (Scheerpeltz 1972, nec Bernhauer 1917) (previously Elecatopselaphus).