Abstract

A sound perspective on epigenetic phenomena must take into account mechanisms and associated phenotypes as occurring in the different lineages of the tree of life. For example, in eusocial insects DNA methylation is involved in caste determination; in ciliate protozoans, the inheritance of cortical structures is independent of DNA and the dramatic DNA rearrangements that give rise to a new macronucleus are epigenetically controlled; in Plasmodium, the parasite responsible for malaria, the continuous turnover in surface proteins is partly under epigenetic control; in flowering plants, the different fates (embryo vs. endosperm) of the zygotes issued from the double fertilization depends on differential epigenetic imprinting. Epigenetic variation contributes to selectable variation and occasionally fosters speciation.