A micro-RNA is the effector gene of a classic evolutionary hotspot locus

In Lepidoptera (butterflies and moths), the genomic region around the gene cortex is a ‘hotspot’ locus, repeatedly used to generate intraspecific melanic wing color polymorphisms across 100-million-years of evolution. However, the identity of the effector gene regulating melanic wing color within this locus remains unknown. Here, we show that none of the four candidate protein-coding genes within this locus, including cortex , serve as major effectors. Instead, a micro-RNA (miRNA), mir-193 , serves as the major effector across three deeply diverged lineages of butterflies, and its function is conserved in Drosophila . In Lepidoptera, mir-193 is derived from a gigantic long non-coding RNA, ivory , and it functions by directly repressing multiple pigmentation genes. We show that a miRNA can drive repeated instances of adaptive evolution in animals. ### Competing Interest Statement The authors have declared no competing interest.