Bees, bats, and moths all follow their noses in search of food from flowers. Plants that rely on such animals for pollination often produce particular chemical scents that attract specific pollinators. However, the ability to produce certain chemicals is also determined by a plant's genetics, or phylogenetic history, which can potentially limit its ability to respond to pollinator pressures. So which is more important in the evolution of floral scents: pollinator-induced natural selection or phylogenetic constraints?
While pollinators are often thought to be the driving force behind the type of chemicals plants produce to attract them, no matter how closely related the plants are to each other, a new study by Kim Steiner and colleagues published in the October issue of the American Journal of Botany (http://www.amjbot.org/content/98/10/1663.full) reveals that phylogeny may be more important than pollinators in determining floral scent characteristics in a group of specialized South African orchids.
"The evolution of any plant or animal character, be it morphological or something as seemingly intangible as a floral scent composed of many specific compounds, is a product of the balancing forces of natural selection and phylogenetic constraint," notes Steiner (University of Kwazulu-Natal, Pietermaritzburg, South Africa).
"While the results of natural selection, or pollinator-mediated selection, generally produce the most fascinating examples of evolution -- such as the extraordinarily long spurs of the Angraecum orchid (Darwin's orchid) and the equally extraordinarily long proboscis of its hawkmoth pollinator -- many characteristics are shared between closely related species simply as the result of their common ancestry, and it is important to be aware that this common ancestry can have a strong influence on the outcome of natural selection," Steiner says.
|Contact: Richard Hund|
American Journal of Botany