The original version of this Article contained an error in Fig. 5, in which the evolutionary origin of DRM2 was incorrectly placed prior to the divergence between gymnosperms and angiosperms . The correct evolutionary origin of DRM2 should be in angiosperms. In addition, in the "Percent methylation change" section of the Methods, Equation 1 was incorrect. This has been corrected in both the PDF and HTML versions of the Article.An amendment to this paper has been published and can be accessed via a link at the top of the paper.