Clarifying the taxonomic status and exploring hidden diversity in <i>Graphomya minor</i> <b>Robineau-Desvoidy, 1830</b> (Diptera: Muscidae: Mydaeinae) using molecular and morphological evidence

A first report on the phylogeography and phylogeny of the widespread Holarctic species, <i>Graphomya minor</i> Robineau-Desvoidy, 1830, within its continuous range throughout northern Eurasia and North America, is presented. The geographic patterns of genetic and morphological variability in <i>G. minor</i> were examined. The phylogenetic structure was assessed using the barcode fragment of the mitochondrial <i>COI</i> gene. We detected 35 unique <i>COI</i> haplotypes in in <i>G. minor</i>, with only two common haplotypes for both the Palaearctic and Nearctic regions. A higher number of <i>COI</i> haplotypes was detected in the Eurasian populations (27 haplotypes) than in the North American samples (eight haplotypes). The diversity of mitochondrial DNA haplotypes and the degree of genetic differences between five geographic populations of <i>G. minor</i> varies. Morphological analysis did not reveal correlations between haplotypes and morphological characters. A genetic comparison of <i>G. minor</i> with morphologically close Palaearctic (<i>G. maculata</i>, <i>G. rufitibia</i>) and Nearctic species (<i>G. ungava</i>, <i>G. minuta</i>, <i>G. americana</i>, <i>G. transitionis</i>) was made. The newly obtained <i>COI</i> sequences of <i>Graphomya</i> species (155) were combined with those published in the GenBank and BOLD databases (76) and were analysed using the species delimitation software ASAP. The results of these species delimitation analyses validated the morphological species in <i>Graphomya</i> and revealed two new species lineages of <i>Graphomya</i> located in north-eastern and south-eastern Russia. Based on the results of our analyses, we concluded that <i>G. minor</i> is a valid widespread polymorphic Holarctic species and is not a junior synonym of <i>G. maculata</i>; and assign 30 unidentified sequences from BOLD and GenBank to named morphospecies.