The fungus gnats of Iceland (Diptera, Keroplatidae & Mycetophilidae)

The Icelandic fauna of fungus gnats in the families Keroplatidae and Mycetophilidae is revised based on available material lodged at the Icelandic Institute of Natural History; the Zoological Museum in Copenhagen, Denmark; the Museum of Zoology in Lund, Sweden; and the Museum of Zoology in Amsterdam, the Netherlands. Eight species names previously published from Iceland are removed from the Icelandic fauna due to misidentifications. Three replaced names and 20 new species are added; viz. Allocotocera pulchella (Curtis, 1837), Sciophila hirta Meigen, 1818, S. parviareolata Santos Abreu, 1920, Boletina basalis (Meigen, 1818), B. gripha Dziedzicki, 1885, Leia fascipennis Meigen, 1818, Anatella sp., Brevicornu auriculatum (Edwards, 1925), B. verralli (Edwards, 1925), Exechia borealis Lundström, 1912 sp. restit., E. micans Lastovka & Matile, 1974, E. pectinivalva Stackelberg, 1948, E. pseudofestiva Lackschewitz, 1937, E. sp. A, Exechiopsis ligulata (Lundström, 1913), Rymosia speyae Chandler, 1994, Mycetophila marginata Winnertz, 1863, Phronia bicolor Dziedzicki, 1889, P. braueri Dziedzicki, 1889, P. taczanowskyi Dziedzicki, 1889, Trichonta atricauda (Zetterstedt, 1852), T. terminalis (Walker, 1856) and Zygomyia pseudohumeralis Caspers, 1980.
The known fauna now comprises 41 species in 19 genera. Keys to genera and males of all species are provided. Females are associated to males and keyed for all species except for species belonging to genera Anatella Winnertz, Brevicornu Marshall and Sciophila Meigen. One male Exechia with rather peculiar but mal-developed terminalia could not be placed in any known species. Hence, it is figured and briefly described here, but left without a scientific name until more material is discovered. Exechia borealis is figured and reinstated as a separate species based on studies of Finnish type material and selection of a lectotype. To confirm the identity of Macrocera nigropicea Lundström, 1906 the Finnish holotype has been studied and compared with the closely related M. maculata Meigen, 1818.
Estimates of the total species richness in Iceland varies between 44 and 52. The Icelandic fauna of fungus gnats is discussed in the context of its relationship to the wider Holarctic fauna, especially to that of the adjacent parts of NW Europe. There is a strong affinity with the rest of NW Europe and a high proportion of the Icelandic species show a Holarctic, seemingly circumpolar distribution. The fauna of fungus gnats in Iceland is regarded to be entirely postglacial in origin. Thus, the dominance of species in the subfamily Mycetophilinae indicates that they are a successful group in the high boreal and arctic regions with a great dispersion potential. The main limiting factor for the diversity of fungus gnats on Iceland is probably lack of highly developed forest environments