Deletion bias in avian introns over evolutionary timescales.

The role that introns play in the function and evolution of nuclear genomes is not fully understood. Recent models of intron evolution suggest that selection and drift may interact to maintain introns in multicellular organisms. In addition, deletion mutations are more likely to become fixed than insertion mutations. Examination of indel substitutions over macroevolutionary timescales in pigeons and doves (Aves: Columbiformes) reveals that deletion substitutions outnumber insertion substitutions by over six times. The length of indel events is variable.