Mitochondrial genome comparison and phylogenetic position of Fannia pusio among the Calyptratae flies

Fannia pusio, the chicken dung fly species, remains unexplored despite its forensic, sanitary, and veterinary importance in the Nearctic and Neotropical regions. In this study, we obtained the complete mitochondrial genome of Fannia pusio for the first time using next-generation sequencing. We compared it with previously published mitogenomes of the genus from the Palearctic region, and its phylogenetic position was studied based on the concatenated proteincoding genes (PCGs) dataset of Calyptratae flies. The circular mitochondrial genome of F. pusio is 16,176 bp in length, with a high A + T content (78.3%), whose gene synteny, codon usage analysis, and amino acid frequency are similar to previously reported Fannia mitogenomes. All PCGs underwent purifying selection except the nad2 gene. Interspecific K2P distances of PCGs of Fannia yielded an average of 12.4% (8.1%-21.1%). The Fannia genus is monophyletic and closely related to Muscidae based on molecular data. Further taxonomic sampling is required to deep into the phylogenetic relationships of the originally proposed species-groups and subgroups within the genus. These results provide a valuable dataset for studying the mitochondrial genome evolution and a resource for the taxonomy and systematics of Fannia.