Revision of the genus Zeller, 1839, a challenging taxonomic tightrope of species delimitation (Lepidoptera, Gelechiidae).

The taxonomy of the Palearctic genus Zeller, 1839 (Lepidoptera, Gelechiidae) is revised, based on external morphology, genitalia and DNA barcodes. An integrative taxonomic approach supports the existence of 85 species which are arranged in 24 species groups (disputed taxa from other faunal regions are discussed). Morphology of all species is described and figured in detail. For 35 species both sexes are described; for 46 species only the male sex is reported, in one species the male is unknown, whereas in three species the female adult and/or genitalia morphology could not be analysed due to lack of material. DNA barcode sequences of the COI barcode fragment with > 500 bp were obtained from 264 specimens representing 62 species or about three-quarters of the species. Species delimitation is particularly difficult in a few widely distributed species with high and allegedly intraspecific DNA barcode divergence of nearly 14%, and with up to 23 BINs in a single species. Deep intraspecific or geographical splits in DNA barcode are frequently not supported by morphology, thus indicating a complex phylogeographic history or other unresolved molecular problems. The following 44 new species (22 of them from Europe) are described: (Spain), (Turkey), (Bulgaria, Romania, Turkey), (Iran), (Croatia), (France, Italy), (Italy), (Spain), (Spain), (Spain), (Portugal, Spain), (Spain), (Spain), (Portugal), (Spain), (Spain), (France, Spain), (Bulgaria, Romania), (Albania, Greece, Macedonia, Montenegro), (Macedonia), (Spain), (Morocco), (France, Spain), (Libya, Morocco), (Kazahkstan), (Kazahkstan), (Spain), (Morocco), (Morocco), (Russia), (Kyrgyzstan), (Kazakhstan), (Afghanistan, Kazakhstan, Kyrgyzstan), (Portugal, Spain), (Morocco), (Algeria, Tunisia), (Turkey), (Croatia, Greece, Italy, Slovenia), (Macedonia), (Spain), (Morocco), (France, Spain), (Afghanistan), and (Afghanistan). Caradja, 1920, (homonym), Dumont, 1928, , Filipjev, 1931, , and Caradja, 1933, are treated as junior synonyms of . Furthermore the following species are synonymised: Staudinger, 1859, ., Walsingham, 1897, ., and Chrétien, 1925, . of (Zeller, 1850); Le Cerf, 1932, of Le Cerf, 1932; (Fischer von Röslerstamm, 1843), and Rebel, 1930, of (Zeller, 1839); Turati, 1924, of (Chrétien, 1915); Junnilainen, 2010, of (Fischer von Röslerstamm, 1843); Povolný, 1982, of (Filipjev, 1929); (Dumont, 1928), , (Dumont, 1928), , and (Turati & Krüger, 1936), of (Chrétien, 1915); Schmidt, 1941, of Meyrick, 1926. (Caradja, 1920), , (Chrétien, 1915), , (Amsel, 1935), , (Chrétien, 1915), , and (Filipjev, 1931), are newly combined in .