Tucked away in the noncoding regions of bird DNA, researchers have discovered molecular roots of the loss of flight seen in so many disparate paleognathous birds. In contrast with previous work, which emphasized changes to protein-coding DNA as driving flightlessness, this study associates loss of flight more strongly with regulatory evolution in noncoding DNA. The results provide an example for future genome studies of so-called convergent phenotypes throughout the animal kingdom. Over time, species of divergent lines of the tree of life can develop similar evolutionary traits. Various species of birds, for example, have experienced the loss of flight many times independently in the course of bird evolution. However, what drives convergent evolution is not well understood; in particular, the underlying genetic changes responsible are a question, with many previous studies implicating changes in protein-coding regions of bird DNA, as opposed to those in regulatory regions. To better understand genetic drivers of the convergent evolution of flightlessness, Timothy Sackton and colleagues investigated the genomes of various ratites, a group of flightless birds that includes the ostrich, kiwi, emu and extinct moa, among others. Sackton et al. combined phylogenetic, developmental and epigenomic analyses of the genomes of ratites, including eleven new genomes, with similar analyses of closely related, flight-capable tinamous. The researchers' analyses suggest that the loss of flight is more strongly associated with changes in noncoding regulatory regions of the DNA, and less so with changes in protein-coding genes, contradicting the results of previous studies. Furthermore, the results indicate that changes in regulatory regions could result in rapid, convergent changes across taxa.
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Science