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

A new classification of Sitonini Gistel into ten genera is proposed, derived from a phylogenetic analysis based on morphology. Two subgenera of Sitona, Charagmus and Coelositona, are promoted to genus level. Sitona is restricted to the former nominotypical subgenus and redefined using apomorphies, and several species previously included in it are transferred to the genus Coelositona González. The species composition of the genus Charagmus Schönherr is unchanged. Andriongen.n. is described (type species: Curculio regensteinensis Herbst, 1794). Catachaenus Schönherr, 1840 is synonymized with Eugnathus Schönherr, 1834 (syn.n.). Homalorhinus lutosus Hochhuth, 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. Andrion does not feed on Hologalegina. Charagmus and Coelositona feed on species of Loteae s.l., whereas members of the genus Sitona feed on species in IRLC. This ability to feed on IRLC plants seems to have been a key trait that enabled the radiation of Sitona into 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. intermedius Küster, 1847, Ch. griseus (Fabricius, 1775), Ch. cachectus Gyllenhal, 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) and Anemeroides lutosus (Hochhuth, 1847).