Researchers writing in the Nov. 13 issue of Nature say perhaps it was a major change or two, such as petal color, that first forged the fork in the evolutionary road that led to today's species of monkeyflowers that are attractive to and pollinated by hummingbirds and separate species of monkeyflowers that are pollinated by bees.
The color change is the result, it appears, of mutation in a single gene, according to H.D. "Toby" Bradshaw, a professor of biology at the University of Washington and lead author of the Nature piece. He says the resulting quick change in pollinator preferences adds to the debate over whether new species arise according to the classic, 150-year-old Darwin theory of evolution that says it may take a hundred small genetic changes, each with mounting effect, or might speciation be kick-started by a few mutations that cause large effects.
"It could be that the first adaptations require a few big changes, sort of like taking a watch that has stopped ticking and banging it a few times before making the small tweaks to restore its optimal performance," says Douglas Schemske, professor of plant biology at Michigan State University and co-author of the letter in Nature.
There are 123 species of monkeyflowers, a wildflower found around the world. Mimulus lewisii appeals to bees with forward-thrusting petals that serve as a landing platform and yellow nectar guides that contrast with the pale pink flowers. The closely related M. cardinalis, on the other hand, has a deep, tubular shape that excludes bees but is easily probed by the slender beaks of hummingbirds, and has red or deep yellow-orange petals, colors bees can't see.