Homologous organs produced by individual plants are not identical, and within-plant phenotypic variance often exceeds variance between plants. Alonso et al. hypothesised that epigenetic mosaicism, caused by subindividual heterogeneity in DNA methylation levels, may account for within-plant variation in seed size and seed production in the evergreen Mediterranean shrub Lavandula latifolia (Lamiaceae).
They found that DNA samples from leaves located in different parts of the same shrub differed in global DNA cytosine methylation, and that such subindividual heterogeneity was nonlinearly related to variation in number and size of seeds produced per inflorescence. They propose that variation in global DNA methylation within L. latifolia shrubs may result from the concerted action of plant sectoriality and differential exposure of different plant parts to some environmental factor(s) with a capacity to induce durable epigenetic changes.