Convergent colour loss in columbines described in Science vol. 314, p1842, 22 Dec 2007 and Molecular Ecology, vol. 15, p4645. Columbines, also known as Aquilegias, are traditional cottage garden flowers that come in many colours, including white. Many columbine species have white varieties, and these are believed to be an adaptation to pollination by hawkmoths. Because white flowers occur in several different species they are considered to be an example of convergent evolution. The colour in the flower petals is due to pigments called anthocyanins. White flowers do not produce anthocyanins. University of California scientists have studied the genes involved in flower colour production in 13 species of columbines. They found “six independent losses and no gain of floral anthocyanins.” Some of the losses involved control genes, rather than genes for enzymes. Claudia Voelckel, one of the researchers, commented: we conclude a lack of convergence at the molecular level when phenotypic convergence results in the loss as opposed to the gain of a trait.” Some genes in the anthocyanin pathway seemed to be unaffected because they seemed to also be used in protecting plants against UV light, insect attack and disease.
Editorial Comment: Did you note that white flower colour is due to loss of functions, and not gain. This study shows what chance random processes really do to biochemical systems. They wreck them. They do not improve them. The “lack of convergence” is simply explained by the fact that there are many ways of making a multi-step system go wrong. The fact that they all result in white flowers is because white is the result of loss of function for many of the steps in the biochemical pathway. This study confirms that convergent evolution is just techno-speak for saying that things that live in a similar environment have similar features and it in no way explains how they got these features. (Ref. flowers, pigments, biochemistry)
Evidence News 14th March 2007