New Insights Into the Evolution of Butterfly Wing Patterns

Nuanced changes to deeply ancestral, multifunctional noncoding genetic elements, rather than the gain and loss of pattern-specific enhancers, have driven the diverse patterns of butterfly wings, according to a study appearing in this week's Science. Butterfly wing patters derive from a deeply conserved developmental ground plan yet are diverse and evolve rapidly. Just how gene regulatory architectures can accommodate both deep homology and adaptive change, however, is poorly understood. To investigate, a Cornell University-led team set out to characterize the cis-regulatory evolution of the color pattern gene WntA, leveraging ATAC-seq and CRISPR knockouts for 46 cis-regulatory elements across five species of butterflies belonging to the family Nymphalidae. They uncovered deep homology of ground plan-determining sequences, except in monarch butterflies, which are quite distantly related to the other species of butterflies included in the study and find that noncoding deletions displayed both positive and negative regulatory effects that were often broad in nature. The results, the authors write, "provide little support for models predicting rapid enhancer turnover and suggest that deeply ancestral, multifunctional noncoding elements can underlie rapidly evolving trait systems.