Systematics of Sitonini (Coleoptera: Curculionidae: Entiminae), with a hypothesis on the evolution of feeding habits

Abstract

AbstractA new classification of Sitonini Gistel into ten genera is proposed, derived from a phylogenetic analysis based on morphology. Two subgenera ofSitona,CharagmusandCoelositona, are promoted to genus level.Sitonais restricted to the former nominotypical subgenus and redefined using apomorphies, and several species previously included in it are transferred to the genusCoelositonaGonzález. The species composition of the genusCharagmusSchönherr is unchanged.Andriongen.n.is described (type species:Curculio regensteinensisHerbst, 1794).CatachaenusSchönherr, 1840 is synonymized withEugnathusSchönherr, 1834 (syn.n.).Homalorhinus lutosusHochhuth, 1847 is removed from Sitonini. The relationships represented by the new classification correspond with the evolution of Fabaceae (Leguminosae), mostly with the group of ‘temperate herbaceous tribes’ or Hologalegina. This group is divided into the sister clades, Loteae s.l. and IRLC (inverted repeat‐lacking clade) – a clade well defined by the loss of a structural mutation in the genome of the chloroplast.Andriondoes not feed on Hologalegina.CharagmusandCoelositonafeed on species of Loteae s.l., whereas members of the genusSitonafeed on species in IRLC. This ability to feed on IRLC plants seems to have been a key trait that enabled the radiation ofSitonainto more than 100 species. A key to the genera of Sitonini and illustrations of important morphological features are provided. A new structure is described from the internal sac, the ‘hamuli’. The variability of hamuli between the species of Sitonini is an important new tool in the taxonomy of this tribe. New combinations:Eugnathus circulus(Eydoux & Souleyet, 1839),E. mangarinicus(Voss, 1925),E. scintillans(Pascoe, 1874),E. sulcifrons(Heller, 1934),Charagmus gressorius(Fabricius, 1792),Ch. intermediusKüster, 1847,Ch. griseus(Fabricius, 1775),Ch. cachectusGyllenhal, 1834,Ch. stierliniReitter, 1903,Ch. variegatus(Fåhraeus, 1840),Coelositona ribesi(González, 1971),C. cambricus(Stephens, 1831),C. cinerascens(Fåhraeus, 1840),C. limosus(Rossi, 1792),C. ocellatus(Küster, 1849),C. latipennis(Gyllenhal, 1834),C. puberulus(Reitter, 1903),C. villosus(Allard, 1869),Andrion regensteinense(Herbst, 1794) andAnemeroides lutosus(Hochhuth, 1847).