Insights into Mitochondrial Rearrangements and Selection in Accipitrid Mitogenomes, with New Data on and .

Background/objectives: Accipitridae mitogenomes exhibit unique structural variations, including duplicated control regions (CRs) that undergo gradual degeneration into pseudo-CRs, revealing a complex evolutionary landscape. However, annotation of this characteristic in a subset of accipitrid genomes is lacking. Due to the taxonomic diversity of Accipitridae and the presence of understudied species, comprehensive mitogenomic studies are essential. This study sought to expand and investigate the evolutionary characteristics of Accipitridae mitogenomes.

Methods: A comparative analysis was conducted using the newly acquired complete mitogenomes of and along with 22 available accipitrid mitogenomes. Codon usage, selective pressure, phylogenetic relationships, and structural variations were comparatively analyzed.

Results: Accipitrid mitogenomes showed a strong AT bias with adenine preference. Most protein-coding genes (PCGs) were under purifying selection except for , which underwent positive selection. The gene exhibited relaxed purifying selection on codon usage patterns and showed high genetic variation. Selection for and genes was specific to certain clades of accipitrids. Gene order re-examination revealed both non-degenerate CRs and highly degenerate CR2 fragments in the Accipitridae family. Non-degenerate CRs were found in early diverging species, such as and , while more recent lineages had highly degenerate CR2 fragments with missing conserved element. Repeat motifs and sequence variations were observed in the functional CR.

Conclusions: These findings suggest that and genes reflect metabolic adaptations, while CRs indicate potential diversification of these accipitrid species. This study provides valuable insights into mitochondrial genome evolution within the Accipitridae family.