High-intensity light promotes adaptive divergence of photosynthetic traits between sun-exposed and shaded populations in Saxifraga fortunei.

Our findings demonstrate that light intensity is a selective pressure that can rapidly promote phenotypic divergence between the sun and shade types. While phenotypic changes in multiple photosynthetic traits were plastic, genetic divergence in specific traits related to adaptation to high-intensity light would be fundamental for ecotypic divergence to different light regimes.