The Mycetophila ruficollis Meigen (Diptera, Mycetophilidae) group in Europe: elucidating species delimitation with COI and ITS2 sequence data

European species of the Mycetophila ruficollis group are compared on the basis of morphology and sequences
of mitochondrial cytochrome oxidase subunit one (COI) and the ITS2 region of nuclear ribosomal
DNA. The study represents the first evaluation of morphology-based species delimitation of closely
related fungus gnat species by applying molecular information. Detailed descriptions and illustrations
of the male terminalia are presented along with a key for the identification of all nine European species
of the group. Phylogenetic analyses of molecular data generally supported the morphological species
discrimination. The barcoding region of COI superseded ITS2 rDNA in resolving species. In the COI
barcoding region interspecific differences ranged from 2.9 to 10.6% and the intraspecific distance from
0.08 to 0.8%. Only COI data distinguished between the similar and closely related M. ichneumonea and
M. uninotata of which the latter was observed to include cryptic species. The host range of some species is
suggested to be narrower than previously considered and to depend on the forest type. Presented evidence
indicates the importance of analysing sequence data of morphologically very similar mycetophages reared
from identified host fungi for elucidating species delimitation as well as their geographic and host ranges.
New country records, viz. Estonia for M. evanida, Georgia for M. ichneumonea, M. idonea and M. ruficollis,
and Norway for M. strobli, widen the known distribution ranges of these species.