By Taylor Nicioli, CNN
(CNN) — When plant biologist Jing-Yi Lu was earning his bachelor’s degree in Taiwan, he began to take note of the local flora. He paid particular attention to the lipstick vines, which, in Taiwan, have short, tubelike flowers with a yellowish-green hue.
However, in other parts of Asia, lipstick vines are known for their long, bright red, tubular flowers, which are primarily pollinated by sunbirds. The green-flowered species are also found across Asia alongside their red counterparts. But in Taiwan, where there are no sunbirds, the red-flowered species does not grow.
Lu wanted to know why the species he was observing in Taiwan looked different from its red-flowered relatives, and what was pollinating it if there were no sunbirds around. But figuring it out was easier said than done.
Typically, when a plant population spreads to an area that lacks its usual pollinators, the plant will strive to adapt, evolving so that it can be pollinated by local wildlife instead. This process is described in the Grant-Stebbins evolutionary model, which explains how pollinators can drive the formation of a new species.
Lu hypothesized that if the plants had come from mainland Asia and spread to Taiwan, they would have evolved shorter flowers so that they could be pollinated by wildlife on the island. But when he and three other biologists looked into the flowers’ DNA, they found something odd: The plants evolved before they spread into Taiwan, contradicting the Grant-Stebbins model.
“It was really surprising,” said Lu, who led the research as a doctoral student at the University of Chicago. Lu is now a research associate at the Field Museum of Natural History in Chicago.
“Because the result did not follow the simple prediction by the classic model, we need to find some alternative explanation for it, and it’s kind of exciting and also kind of puzzling,” Lu added.
Lu’s discovery, which was detailed in a paper published in January in the journal New Phytologist, highlights an exception to the long-standing evolution model.
But a mystery remains: Why would the flowers evolve before spreading into a new area, instead of the other way around? The researchers have some theories.
Oddball flower evolution
The lipstick vine with green flowers, known as Aeschynanthus acuminatus, is found across Southeast Asia, including northern India, the Himalayas, Vietnam, Thailand, southern China and Taiwan, according to a news release from the Field Museum.
To find out which birds were pollinating these flowers in Taiwan, researchers set up camera traps and found that various birds with shorter beaks than the mainland pollinators were visiting the lipstick vines, a result of the plants having a shorter and wider flower. On the mainland, they found shorter-beaked birds were also pollinating the green flowers in addition to the sunbirds that were capable of feeding from the shorter tubes as well as the longer, red flowers.
But when researchers looked into the lipstick vines’ family tree by extracting and analyzing the plant’s DNA, they found that the green flower species descended from plants on the mainland. Despite having long-beaked sunbirds to pollinate their flowers, the mainland plants had split and evolved to have shorter green flowers that supported a wider range of pollinators.
“It turned out to be that the data did not support the simplest explanation. It required a more complicated explanation. Ultimately, it still remains kind of mysterious, how plants switch from one pollinator to another and evolve into new speci