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

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

Automated summary

This study presents the first report on the phylogeography and phylogeny of Graphomya minor, a widely distributed species in northern Eurasia and North America. The mitochondrial COI gene analysis revealed a higher genetic diversity in the Asian populations of G.minor. However, morphological analysis did not show any correlations between haplotypes and morphological characters.