The molecular machinery regulating flowering has mainly been studied in Arabidopsis and crop plants but is also important for understanding the dynamics of ”wild” plant populations and the spread of invasive species. The present project will involve the wild flower Crepis tectorum (“klofibbla”). C. tectorum has undergone considerable divergence in phenology, especially in regions where the common weed type (subsp. tectorum) grades into specialized forms adapted to rock outcrops (e.g. the Öland endemic subsp. pumila). The outcrop forms start to flower 2 or 3 weeks earlier than the weed ecotype, thus avoiding the risk of desiccation in the drought-prone outcrop habitat. The phenological differences within C. tectorum have a strong heritable basis according to common-garden and crossing experiments. The underlying molecular and physiological mechanisms remain unknown. We now have RAD sequence data from 24 early and 24 late plants, and we will now look for markers associated with those phenotypes.