Linked from
The 28 pages that link to Somatic mutation, each with the reason it gives.
MosaicismRelated: A mutation in an embryonic cell can create a genetically distinct lineage.
Clonal colonyRelated: Mutations can make different parts of an old colony genetically distinct.
Clonal evolutionRelated: New somatic mutations create heritable differences among cell lineages.
MutagenRelated: Mutagen exposure can create mutations confined to affected tissues.
Old TjikkoRelated: Mutations can distinguish successive shoots within a long-lived plant clone.