Understanding Natural Epigenetic Variation

Recently, there has been increased interest in understanding the role of epigenetic processes in ecology and evolution (e.g. Richards, 2006; Bossdorf et al., 2008; Johannes et al., 2008; Richards et al., 2010). We now know that some epigenetic marks are not reset each generation, but are faithfully transmitted across generations (Jablonka & Raz, 2009), that natural variation can exist not only in the DNA sequence but also at the epigenetic level (e.g. Vaughn et al., 2007) and that epigenetic variation can cause significant heritable variation in phenotypic traits (e.g. Johannes et al., 2009). Moreover, heritable epigenetic modifications can be triggered by exposure to different environmental conditions (e.g. Verhoeven et al., 2010). If we put these different pieces of evidence together, then this clearly suggests that epigenetic mechanisms could add an additional layer of complexity to heritable phenotypic variation, and thus to the diversity and evolutionary potential of natural populations. However, in spite of abundant speculation about the potential ecological and evolutionary implications of epigenetic processes, most previous work has been carried out on only a few types of agricultural crops and on model species such as Arabidopsis thaliana, frequently under artificial conditions, and we therefore still have no idea of the true importance of epigenetic processes in natural populations. Because of this, several authors have argued for expanding research efforts into ecologically relevant circumstances across model and nonmodel organisms and have outlined experimental and statistical approaches that would facilitate the merging of molecular-based insight with sound evolutionary ecology (Bossdorf et al., 2008; Johannes et al., 2008; Richards, 2008). In this issue of New Phytologist(pp. 867–876), Herrera & Bazaga provide an intriguing example of how researchers are now beginning to respond to this call. ‘… epigenetic mechanisms could add an additional layer of complexity to heritable phenotypic variation, and thus to the diversity and evolutionary potential of natural populations.