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Relaxed selection and the evolution of Chasmogamous flower of Impatiens capensis

Citation

Schoen, Daniel; Zhao, Yi (2022), Relaxed selection and the evolution of Chasmogamous flower of Impatiens capensis, Dryad, Dataset, https://doi.org/10.5061/dryad.wstqjq2nw

Abstract

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 flowering in plants of both ecotypes. Contrary to our predictions, geometric morphometric analysis of sepal shape variation levels indicated little difference between the shade and sun ecotypes. We suggest that mutations that influence CH flower shape may have pleiotropic effects on structures or processes that remain under selection even when the CH flowers are not produced. On the other hand, sepal size was significantly smaller in the shade ecotype populations. In the case of CH sepal size, the mutational effects appear to be directional, towards the production of smaller sepals, and likely would be deleterious if shade ecotype plants encountered sunnier conditions where CH flowers could be produced.  

Methods

Please refer to the Methods and Results section of the article and to the README file.  The data files submitted include landmark and semi-landmark data for the flower, growth response to red-far red and control treatments of plants from different populations, and maternal effects testing.

Usage Notes

Please refer to the Methods and Results sections of the article, and the Read_Me.txt file uploaded with the individual data files.

Funding

NSERC, Award: RGPIN-2017-04494