Pioneering Pollinator Research Reveals Genetic Clues to Darwin’s “Abominable
Research into the flower preferences of pollinating moths may have delivered a vital clue to the simple factors needed for the emergence of new species.
Strong coevolutionary relationships between plants and animal pollinators have long been recognized as a potential driver of high rates of speciation in the 275,000 extant flowering plants. Shifts between pollinators, such as bumblebees, hummingbirds, hawkmoths, and bats, often coincide with plant speciation events.
Each of these pollinator “guilds” is attracted by a different set of floral traits such as color, patterns, scent, shape, and nectar reward, collectively known as a pollination syndrome.
So far, the detailed genetics of traits involved in pollinator shift-driven speciation remain unclear except in a few developing model systems.
In a new study, researchers set out to engineer a pollinator switch in the lab that could mirror the origin of a new species in nature.
They selected a species in the genus Mimulus (monkeyflowers) section Erythranthe where the evolution of hawkmoth pollination from hummingbird pollinated ancestors has not occurred.
They made genetic changes to two flower color genes – effectively synthesizing a new Mimulus species with lower levels of the red pigment anthocyanin and yellow carotenoid pigments. These changes were based on observations in nature that most hummingbird-pollinated flowers are red and not easily visible to hawkmoths whose visual sensitivity does not extend to longer, red-light wavelengths. Hawkmoth-pollinated flowers, in contrast, are usually white or pale and highly reflective, adapted for detection by the crepuscular and nocturnal hawkmoths.
Researchers tested the attractiveness of the four resulting color phenotypes – red, yellow, pink, and white – using lab-reared hawkmoths with no previous exposure to flowers.
Hawkmoths strongly preferred “derived” non-red colors – yellow, pink, and white – over the ancestral red favored by hummingbirds and visited these pale colored flowers more often and for longer total periods over the experimental period.
The study found that just these two simple genetic changes engineered by the researchers were required to affect the preference of hawkmoth pollinators.
“We expected the hawkmoths to show some preference between colors, but their preferences were extremely strong,” said first author Dr. Kelsey Byers of the John Innes Centre and formerly based at the University of Washington (Seattle, WA, USA) where this research took place.
“Our study shows that changes in flowering plant pollination syndrome can proceed through relatively few genetic changes, and this further suggests that only a few simple genetic changes might be required for the origin of a new species,” she added.
Charles Darwin – fascinated by what he described as the “abominable…