Although Charles Darwin is most well-known both for his book "On the Origin of Species" and his theories on natural selection, he once stated, "I do not think anything in my scientific life has given me so much satisfaction as making out the meaning of the structure of these plants." What could be more satisfying than unraveling the mysteries of evolution?
Darwin was referring to his studies of different forms of hermaphroditic flowers that occur in a single species. In "'A case to which no parallel exists': The influence of Darwin's Different Forms of Flowers," published in the May issue of the American Journal of Botany, James Cohen discusses Darwin's pioneering work concerning the complex breeding system known as heterostyly and what scientists have discovered since Darwin's time.
"Heterostyly is one of, if not the most, complex type of breeding system found in flowering plants. The presence of heterostyly affects the morphology, ecology, development, genetics, and evolution of a species. Given the far-reaching effects of the complex breeding system, along with the fact that it appears to have evolved over 40 times independently, it is fascinating to think about the function and evolution of heterostyly," Cohen commented.
In heterostylous species, two or more different forms of flowers with both male (anthers) and female (stigmas) parts exist. The anthers and stigmas are at different heights within each form, with the anthers of one flower at the same height as the stigmas of the other flower.
Darwin stated, "The benefit which heterostyled dimorphic plants derive from the existence of the two forms is sufficiently obvious, namely, the intercrossing of distinct plants being thus ensured. Nothing can be better adapted for this end than the relative positions of the anthers and stigmas in the two forms."
"Darwin, along with many of his contemporaries, understood the importance of outcrossin
|Contact: Richard Hund|
American Journal of Botany