Our laboratory's study of Lasthenia (Asteraceae) began with an examination of flavonoid profiles of all species of the genus. The finding of two distinct flavonoid races within the L. californica complex led us to investigate environmental factors that might have been responsible for selection of these particular forms. Data were gathered on soil chemistry, allozyme variation, breeding biology, the effect of water stress on plant growth, and ion uptake physiology. In conjunction with workers at other institutions, DNA studies were undertaken to determine evolutionary relationships between the two races. These studies led to the recognition that racial differences had arisen in parallel in two phylogenetically independent lineages. These results are discussed in terms of the evolution of edaphic (soil type) races, and the possible usefulness of the system as a model for future studies of parallel speciation in plants.
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