Comparative mitogenomic study of the brown accentor (Prunella fulvescens) and a sympatric relative across an altitudinal gradient

The Brown Accentor (Prunella fulvescens) is an understudied bird on the Tibetan Plateau, for which life-history and molecular genetic data remain scarce. In this study, we sequenced the complete mitochondrial genome of P. fulvescens and conducted a comparative analysis with two conspecific individuals (one from the similar altitude and one from a lower altitude); we further performed interspecific comparison with its sympatric species Prunella strophiata (a congener) and Carpodacus rubicilloides (a sympatric non-congener). Divergence between high and lower altitude populations of P. fulvescens concentrated in genes associated with oxygen utilization and energy metabolism. As altitude decreased, the number of mutation sites increased (except for Cyt b). ATP8 has the lowest nucleotide and amino acid sequence similarity across both groups. Ka/Ks analysis indicated that ATP6 and COXIII evolve at a faster rate. Sympatric interspecies comparisons revealed that different genes exhibit varying intensities of selective pressure, reflecting their respective functions. Divergence time estimation showed that divergences among the three P. fulvescens populations occurred during the Pleistocene. Collectively, these findings suggest incipient genetic differentiation among P. fulvescens populations at different altitudes, driven by geographic isolation and environmental adaptation. This study provides novel insights into the genetic basis of high-altitude avian adaptive evolution.