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Puerto Rico Lizard Study Points to Parallel Evolution in Cities

In a paper slated to appear in the Proceedings of the National Academy of Sciences this week, researchers at Princeton University, Washington University, the University of Massachusetts Boston, and elsewhere document adaptations found in small neotropical Puerto Rican crested anole (Anolis cristatellus) lizards living at urban sites in Puerto Rico. Using a custom exon capture array, the team considered 96 lizards from half a dozen urban or forest populations, unearthing parallel genetic features that contribute to the physical adaptations found in anoles accustomed to city living, such as longer-than-usual limbs and larger toe pads. Along with a set of 93 candidate genes with apparent ties to the traits of interest, the author saw signs that rapid adaptation at urban sites tended to involve polygenic selection on standing variation. "Identified candidate loci represent several functions associated with skeletomuscular development, morphology, and human disease," they report, adding that the urban lizard findings "shed light on the genomic basis of complex morphological adaptations, provide insight into the role of contingency and determinism in adaptation to novel environments, and underscore the value of urban environments to address fundamental evolutionary questions."