Figure 1

Innovations of microRNAs, tandem duplications, and non-local duplications of microRNA genes are unevenly distributed in metazoan phylogeny. Indeed, non-local duplications occur almost exclusively in the ancestral vertebrate and teleosts, resp., in accordance with the 2R/3R model. Species for which large experimental screens for microRNAs have been performed are indicated by a larger font. The phylogenetic tree is based on a recent multi-gene analysis of the major bilaterian groups [69], and the phylogeny of holometabolous insects [70].