Conservation of miRNA editing in vertebrates. The identifier of the edited miRNA and the position at which editing occurs are indicated on the left. Observed miRNA editing with a frequency of >1% is indicated as blue boxes for the species in the core set (Table 1) and as dark green boxes for the 10 additional species. For completeness, cases where A-to-G mismatches were present at a frequency <1% (‘trace reads’) are shown as light green boxes, although it should be noted that such trace events cannot be readily distinguished from sequencing errors. Gray shading indicates that the presence of miRNA editing could not be assessed due to a lack of sequencing reads for the miRNA in question (which might be explained by the rigorous filtering criteria, lack of expression in the investigated samples or absence of the miRNA in the genome). An asterisk following the species name indicates that no quality scores were available for the species in question. Divergence times were taken from the TimeTree database . Note that the analysis presented here was performed using a stringent detection algorithm to avoid false positives; editing of a given miRNA might therefore have escaped detection in some species (compare Figure 3).