Irene Adrian-Kalchhauser, Sonia E Sultan, Lisa Shama, Helen Spence-Jones, Stefano Tiso, Claudia I Keller Valsecchi, Franz J. Weissing

Understanding the evolutionary and ecological roles of non-genetic inheritance is daunting due to the complexity and diversity of epigenetic mechanisms. We draw on precise insights from molecular structures and events to identify three general features of non-genetic inheritance systems that are central to broader investigations: (i) they are functionally interdependent with, rather than separate from, DNA sequence; (ii) each of these mechanisms is not uniform but instead varies phylogenetically and operationally; and (iii) epigenetic elements are probabilistic, interactive regulatory factors and not deterministic epi-alleles with defined genomic locations and effects.
We explain each feature and offer research recommendations. Finally, we consider existing evolutionary models for non-genetic inheritance and present a new model that implements a unifying inherited gene regulation approach.