Mosaic Accumulation of Somatic Genetic Variation and Estimates of Age in the Long‐Lived Reef‐Building Coral Acropora palmata

ABSTRACT Somatic genetic variation (SoGV) accumulates during an organism's lifetime and is traditionally viewed as detrimental rather than adaptive due to links with cancer and senescence. However, in modular organisms like corals, deleterious mutations can be purged at the cellular or polyp level, while adaptive mutations may rise in frequency as polyps create genetically distinct modules. Quantifying the somatic genetic landscape in corals is necessary to understand the role these mutations may have in coral and clonal animal development and evolution. Here, we catalogue somatic genetic variation in eight Acropora palmata colonies from Curaçao. Whole genomes were sequenced (70–100× depth) to document mutation variant allele frequency shifts as genets age. Large numbers of SoGVs were observed in six‐ to ten‐year‐old colonies, and inferred mutation rates were used to age a genet of uncertain age to almost a century old. Mutations were not fixed at the polyp or branch levels, i.e., they always displayed frequencies Acropora palmata . This work provides fundamental insights into the landscape of somatic mutations in reef‐building coral, highlighting the importance of studying somatic genetic variation as they may contribute to genetic diversity and adaptability in colonial animals.