Variation in DNA methylation transmissibility, genetic heterogeneity and fecundity-related traits in natural populations of the perennial herb Helleborus foetidus

Inferences about the role of epigenetics in plant ecology and evolution are mostly based on studies of cultivated or model plants conducted in artificial environments. Insights from natural populations, however, are essential to evaluate the possible consequences of epigenetic processes in biologically realistic scenarios with genetically and phenotypically heterogeneous populations. Here, we explore associations across individuals between DNA methylation transmissibility (proportion of methylation-sensitive loci whose methylation status persists unchanged after male gametogenesis), genetic characteristics (assessed with AFLP markers), seed size variability (within-plant seed mass variance), and realized maternal fecundity (number of recently recruited seedlings), in three populations of the perennial herb Helleborus foetidus along a natural ecological gradient in southeastern Spain. Plants (sporophytes) differed in the fidelity with which DNA methylation was transmitted to descendant pollen (gametophytes). This variation in methylation transmissibility was associated with genetic differences. Four AFLP loci were significantly associated with transmissibility and accounted collectively for ~40% of its sample-wide variance. Within-plant variance in seed mass was inversely related to individual transmissibility. The number of seedlings recruited by individual plants was significantly associated with transmissibility. The sign of the relationship varied between populations, which points to environment-specific, divergent phenotypic selection on epigenetic transmissibility. Results support the view that epigenetic transmissibility is itself a phenotypic trait whose evolution may be driven by natural selection, and suggest that in natural populations epigenetic and genetic variation are two intertwined, rather than independent, evolutionary factors.