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Relationships between soil chemistry and floral morphology in Collinsia sparsiflora, a native California annual.
Wright, Jessica*,1, Stanton, Maureen1, Scherson, Rosa1, 1 University of Califonia, Davis, CA, USA
ABSTRACT- Serpentine soils are a challenging place for plants to grow. They have low levels of nutrients, a skewed Mg:Ca ratio and high levels of heavy metals. But rather than being barren wastelands, these soils support a diverse flora that, particularly in California, acts as a refuge for a high number of native species. One of those species is Collinsia sparsiflora, a native California annual which has the ability to grow both on and off of serpentine soils. At the McLaughlin Natural Reserve, C. sparsiflora plants growing on non-serpentine soils have small white flowers while plants growing on serpentine soils have much larger, showier purple flowers that appear to be adapted for outcrossing. Both ecotypes are capable of automatic self-fertilization, however, suggesting that if this divergence in floral form is genetically based, it may be driven in part by adaptation to edaphic factors. A reciprocal transplant experiment was used to study the relationship between source population effects and those of the local environment on three floral characteristics: flowering date, flower color and flower size. Flowering date was very strongly influenced by the local environment- plants flowered earlier on serpentine soils, regardless of where they came from. Flower color was not influenced by the local environment. For example, white flowered non-serpentine plants did not produce purple flowers on serpentine soils. Flower size showed a combination of source population and environmental effects- plants produced the longest flowers on their home soil type. Crosses between populations support the conclusion that flowering date is strongly influenced by the environment, while flower color is under strong genetic control, and flower size is influenced by a combination of factors. These results suggest that the relationship between soil chemistry and floral morphology in C. sparsiflora is highly complex and that the response to selection on these traits could be highly dependent on the effects of the local environment.
Key words: Collinsia sparsiflora, Serpentine soil, floral characters, reciprocal transplant