INDIVIDUAL VARIATION IN SIZE AND FECUNDITY IS CORRELATED WITH DIFFERENCES IN GLOBAL DNA CYTOSINE METHYLATION IN THE PERENNIAL HERB HELLEBORUS FOETIDUS (RANUNCULACEAE)

Premise of the study: Few studies have examined how epigenetic modifications of DNA may influence individual plant phenotypes and ecological processes in wild plant populations. We investigated natural variation in global DNA cytosine methylation and its phenotypic correlates in the perennial herb Helleborus foetidus. Methods: We focused specifically on individual differences in size-and fecundity-related traits and used HPLC to quantify percentage of total cytosines in the genome of young full-grown leaves that were methylated. Key results: About one third of all cytosines in H. foetidus genome were methylated. Methylation level differed significantly among individual plants (range = 26.4-36.6%; n = 60 plants), and this variation was significantly related to most size-and fecundity-related traits considered. Relatively hypomethylated plants bore more vegetative, reproductive, and total ramets, produced more flowers, larger inflorescences and more seed-bearing follicles, and their ramets remained vegetative for fewer years before reproducing sexually, than relatively hypermethylated ones. Taken together, results revealed that individual differences in size and reproductive output were inversely related to global cytosine methylation. Conclusions: These results confirm, in a natural scenario, the association between DNA methylation and size-and fecundity-related traits that was previously found by experimental studies. Variations in global cytosine methylation were predictably related to individual differences in sexual reproduction through significant effects on flower and fruit production, which might ultimately influence patterns of selection and population dynamics in this species. This study provides novel insights on the potential ecological significance of epigenetic heterogeneity in wild plant populations.