Systematics of Cetema Hendel (Diptera: Chloropidae):: revision of the Nearctic species and phylogeny and zoogeography of the Holarctic fauna

The Holarctic genus Cetema Hendel is revised, with special reference to the Nearctic fauna. There are four Nearctic species: C. elongata Meigen; C. nigripalpis sp. n., C. procera Loew, and C. subvittata Loew. This is the first record of the Palaearctic species C. elongata in the Nearctic region. All Nearctic species are described and illustrated. The Palaearctic species C. paramyopina Collin is synonymized with C. neglecta Tonnoir and a key to all described species of Cetema is provided. A phylogenetic analysis supports the monophyly of the genus, as well as the monophyly of the subgenera Archecetema Nartshuk and Cetema. The Nearctic species do not form a monophyletic group. Zoogeographic analysis suggests that the genus originated in the eastern Palaearctic and subsequently colonized North America via a Beringian connection, probably in the early to mid-Tertiary. Following speciation in the eastern Nearctic, the more derived lineages of Cetema recolonized the western Palaearctic, probably via a North Atlantic land connection prior to the late Miocene.