Relaxed selection and the evolution of Chasmogamous flower of Impatiens capensis

We exploited ecotypic variation in Impatiens capensis to test the hypothesis that mutation accumulation accompanying relaxed selection on the chasmogamous (CH) flower leads to more variable flower shapes and smaller flowers. Sun ecotype populations of this species occur along sunny riverbanks and marshes and produce both CH and cleistogamous (CL) flowers, while shade ecotype populations occur in shady forest floors and produce only CL flowers. In the shade ecotype, it is assumed that selection on the CH flower has been relaxed. Seedlings from population samples of the two ecotypes exhibited different first internode growth responses to low ratio of red:far-red light characteristic of ecotypic differentiation to either sunny or shady conditions, helping to verify historical illumination conditions in the populations. We examined the CH floral mutation accumulation hypothesis by comparing the shape and size of the modified CH flower sepal under greenhouse conditions that triggered CH flow...