Characterization of the Complete Mitochondrial Genome of Sea Duck Mergus serrator and Comparison with other Anseriformes Species

As a key group in the Anatidae, the Mergini tribe (sea ducks) is strongly structured, with clear genetic assignments and phylogenetic relationships. The tribes also differ in terms of breeding strategy, longevity, and bionomic strategy. The mitochondrial genome (mitogenome) of Mergus serrator was 16,627 bp in length, and its structure was circular. The structure and gene arrangement of the genome were basically the same as those of Anseriformes species. The mean base composition of the mitogenome of Anseriformes was T (22.31 +/- 0.51%), C (32.63 +/- 0.64%), A (29.36 +/- 0.64%), and G (15.71 +/- 0.52%), indicating a slight specific bias towards A and C. AT content ranged of the mitogenome was from 50.27% to 55.31%, with an average value of 51.67 +/- 1.10%, higher than the GC content and similar to that of birds in general (50.5% to 57.7%). In addition, the start and stop codons, the mitogenome consists of 3662 codons. The most commonly used amino acid was leucine (13.63%) in the use of M. serrator. The analyses indicated that the Anseriformes include the families Anseranatidae, Anhimidae, and Anatidae. Furthermore, Anatinae is composed of Aythyini, Anatini, Somaterini, and Mergini. M serrator was sister to M. merganser and M. squamatus, and this group belongs to Mergini. The. value of the ND3 gene in the Mergini tribe is lower than those for other tribes. The phylogenetic relationships were analyzed and M. serrator was sister to M. merganser and M. squamatus, and formed a closely evolved Mergini clade. Different evolutionary rates between the Mergini tribe and other tribes were found.