Mouthpart structure of Stylogymnusa subantarctica Hammond, 1975 (Coleoptera : Staphylinidae : Aleocharinae) with a reanalysis of the phylogenetic position of the genus

Structure, particularly of the mouthparts, of the unusual aleocharine staph ylinid Stylogymnusa subantarctica Hammond was reevaluated. The mouthparts a re described in detail, and drawings of their structure are provided. Sever al features were found to be misinterpreted in previous accounts of the str ucture of this aleocharine. In particular, the stylate structures found on the prementum are not a highly; modified, hollow stylate glossa, as had bee n previously suggested. Instead, these structures represent highly modified labial palpi; the segments are completely fused, all signs of typical seta e of the labial palpi are missing, and the palpi are very long and slender. In addition, there is no sign that they are hollow. Small, slender, membra nous lobes at the base of, and between, the palpi are interpreted as the tr ue glossae (= ligula). Reinterpretation of these characters, and greatly im proved phylogenetic techniques in the 20 years since previous phylogenies h ad been proposed, allowed testing of previous hypotheses of the phylogeneti c position of Stylogymnusa and the relationships of the tribes Gymnusini an d Deinopsini within the Aleocharinae. Phylogenetic analysis of 7 out-group and 12 in-group taxa, based on 84 characters and 231 character states, prod uced 3 equally most-parsimonious trees (tree length = 253, C.I. = 0.557, R. I. = 0.674, rescaled C.I. = 0.376). These trees provide strong support for a monophyletic lineage consisting of Stylogymnusa, Gymnusa and the Deinopsi ni but only weak support for a monophyletic Gymnusini (Gymnusa + Stylogymnu sa). Bootstrap analysis based on 1000 resampling repetitions showed the fol lowing monophyletic clades to be well supported by the dataset: Aleocharina e (79%), Stylogymnusa + Gymnusa + Deinopsini (99%), Deinopsis + Adinopsis ( 100%), and representatives of Myllaenini + Athetini + Aleocharini + Homalot ini + Oxypodini (the "higher Aleocharinae") (88%). Weakly supported clades in the bootstrap analysis were: Paraconosoma + Gymnusini + Deinopsini (56%) , Anacyptus + 'higher Aleocharinae' (54%), and Athetini + Oxpodini + Homalo tirli + Aleocharini (52%). (C) 2000 The Linnean Society of London.