Characterization Of The Complete Mitochondrial Genome Of Sea Duck Mergus Serrator And Comparison With Other Anseriformes Species

Background: 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 Mergini tribe as an excellent tribe to investigate molecular adaptions to elevate metabolic burden associated with other life-history characteristics. Mitochondrial genome (mitogenome) plays a critical role of molecular evolution and phylogenetic. Phylogenetic analyses can help investigate the relationships between mitochondrial DNA (mtDNA) molecular evolution and metabolic performance. Results: The mitogenome of Mergus serrator was 16,627 bp in length, and its structure was circular. Annotation of the mitogenome presented 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and 1 control region. To determine the intraspecific evolutionary relationships among Anseriformes, the mitogenomes of 53 other Anseriformes species were examined concurrently. Among Anseriformes species, the shortest mitogenome belongs to Oxyura jamaicensis (15,914 bp) and the longest is that of Anseranas semipalmata (16,868 bp). 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 (Table 1) and similar to that of birds in general (50.5% to 57.7%). Conclusions: The structure and gene arrangement of the genome were basically the same as those of Anseriformes species. 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 results of selection analysis demonstrated different evolutionary rates between Mergini tribes and other tribes, and most protein-coding genes evolved under purifying selection except for the ND6 gene.