Adaptive Evolution of Pelvic Reduction in Sticklebacks by Recurrent Deletion of a Pitx1 Enhancer

Abstract

Adaptive Girdle Loss in Sticklebacks: How do molecular changes give rise to phenotypic adaptation exemplified by the repeated reduction in the pelvic girdle observed in separate populations of sticklebacks? Now Chan et al. (p. 302 , published online 10 December) have identified the specific DNA changes that control this major skeletal adaptation. The key locus controlling pelvic phenotypes mapped to a noncoding regulatory region upstream of the Pituitary homeobox transcription factor 1 gene, which drives a tissue-specific pelvic enhancer. Multiple populations showed independent deletions in this region and enhancer function was inactivated. Reintroduction of the enhancer restored pelvic development in a pelvic-reduced stickleback.