Lineage-specific accelerations in mitochondrial genomes of Campanuloideae

In plants, the mitochondrial genomes tend to evolve slowly in sequence. Here, we displayed a significant departure from this conserved evolutionary pattern in two lineagesof flowering plants. Nucleotide substitution rates vary substantially between lineages of Platycodinae+Wahlenberginaeand Campanulinae within the subfamily Campanuloideae. All mitochondrial genes accelerated in Platycodinae+Wahlenberginae, indicating that substitution rates accelerated throughout the genome. Additionally, we tested the hypotheses regarding biological mechanisms underlying this pattern.