UCSB researchers document stark evolutionary change in flowers

Researchers at UC Santa Barbara have documented an abrupt evolutionary change in blue columbine flowers. The results suggest that natural selection may not always be a sequence of gradual changes, but may instead occur more suddenly.

Scott Hodges, a UCSB professor, is an evolutionary biologist specializing in pollination systems. He studies the blue columbines of Colorado.

Hodges’ Pollination Research, with Ph.D. student Zachary Cabin, discovered something unexpected. Hodges said their data shows about a quarter of blue columbine plants in Colorado have lost their petals and nectar spurs for pollination.

“For all of a sudden to find a case where we lost this feature of the plant that seemed so important was really surprising,” Hodges said.

Hodges said they initially thought the change disadvantaged the plant since pollination contributed to reproductive success.

“But it had nothing to do with pollinators. It had everything to do with being less likely to get eaten,” he said.

Cabin said deer and aphids prefer flowers with nectar spurs, so becoming spurless is likely driven by selective pressure for plant survival.

“Herbivores apply such strong pressure that the way to avoid this is to lose that sweet, sweet flavor,” Cabin said.

He said mutations are not unusual, but changes of this magnitude indicate evolution.

“It’s really unlikely that there would be such a high number in the population due to what we call genetic drift or random processes, we would expect selective pressure to be the cause of this” , did he declare.

Cabin said a change in the plant’s appearance was noted by botanists in Colorado about 120 years ago, but no comprehensive study has been done.

With extensive field data and DNA analysis from a collaborative lab, Cabin said the lack of spines can now be attributed to a change in a single gene. The gene, he says, is turned on or off and controls all the development of flower spurs and nectaries.

Professor Hodges said the research contributes to the understanding of evolution.

“Darwin’s idea was that evolution happens in these very small changes, so you would make a very small change and it would have a small benefit, but you should have another small change, and another,” Hodges said. . “What we’ve been able to show here is that you can have one change and do a really big jump all at once.”

The study was published in the journal Current Biology.