Citizen science photos and AI reveal how switchgrass adapts across a continent

Citizen science photos solve a switchgrass mystery

Every summer, millions of people snap photos of wildflowers and upload them to nature apps without a second thought. Those casual photos, it turns out, may be doing serious science. In a new study, researchers took nearly 44,000 of those crowd-sourced images and used them to reveal how plants survive across a continent. The team, led in part by Professor Jianming Yu at Iowa State University, combined that photo database with controlled field experiments and genetic analysis. The goal was to answer a question that has long puzzled ecologists: why does the same plant species behave so differently depending on where it grows? "With this study, we have connected our quantitative genetic and genomic research with ecology, evolution and adaptation over a large-scale landscape," said Yu. "The beauty is we're bridging them together so we can see the whole picture." A robot that spots flowers The researchers focused on four common North American prairie grasses: switchgrass, big bluestem, Indiangrass, and little bluestem. These grasses grow from Texas to the Canadian border, and tracking when they flower across that entire range would normally take field workers years. Instead, the team built an AI tool called FLORIST and ran it across a massive online photo archive from GBIF, the Global Biodiversity Information Facility, fed largely by contributors to iNaturalist. Citizen science reveals patterns FLORIST scanned each image for signs of active flowering. Out of nearly 44,000 photos, the tool identified around 5,000 observations of plants caught mid-bloom, each tagged with GPS coordinates and a date. The pattern was immediately clear. Across all four species, plants growing farther north flowered earlier in the year. That made intuitive sense. Northern summers are short, winters come fast, and plants need to finish flowering before the cold arrives. The experiment showed otherwise Here is where the story gets interesting. The same team had also spent two years growing switchgrass at ten research sites across the Midwest and Gulf regions. In these controlled experiments, hundreds of genetically distinct plants grew side by side under identical conditions. In those experiments, the trend flipped completely. Plants from northern origins flowered later than plants from southern origins, by about 2.3 days per degree of latitude northward. "We had to wrap our minds around that," said Yu. Two datasets about the same plant were telling two completely different stories. Rather than trust one and discard the other, the team set out to understand how both could be true. The answer was in the genes The resolution came from genetics. By analyzing the DNA of hundreds of switchgrass plants from across their native range, the researchers identified three key genes that control when the plant flowers. The genes, called GI, Hd1, and FTL1, act like a biological clock that reads environmental signals and decides when to bloom. These genes come in different versions. Plants from the Gulf region carry one combination of variants, called H1. Plants from the Midwest carry a different combination, called H2. The two versions do not respond to their environment in the same way. H2 plants are highly sensitive to spring temperatures and flower quickly when April and early May run warm. H1 plants flower much later regardless of that spring warmth, and they shift far less in response to temperature changes. Plants that adapted for survival This difference is not random. It is adaptation in action. In the north, flowering early is a survival necessity. Winters arrive hard and fast, and H2 plants need to reproduce before the cold shuts everything down. The researchers saw this directly during the severe winter of 2018, when H1 plants at northern garden sites suffered devastating losses while H2 plants came through largely unscathed. In the south, the danger runs the other way. Switchgrass pollen is remarkably fragile in heat, surviving less than ten minutes at 32 degrees Celsius (89.6 degrees Fahrenheit). H1 plants delay flowering until late summer, after the worst heat passes. H2 plants grown in the south would flower at the peak of summer and effectively destroy their own pollen. "In their native conditions, both haplotypes are doing the things that they need to do to survive and thrive," Yu said. "In the north, they flower earlier because winter is coming. But in the south, there's no rush because summer is so hot and the fall is mild." Two datasets, one true picture The contradiction dissolved once the team accounted for which gene version each plant carried and what temperatures it experienced. The citizen science photos captured real plants already equipped with the gene version suited to their location. The field experiments mixed all gene versions across all environments, revealing the underlying genetic baseline rather than what actually plays out in nature. Neither dataset was wrong. They were showing different parts of the same picture. "Our study highlights the power of combining citizen science observations with designed experiments to uncover mechanisms of adaptation across spatiotemporal scales," noted the researchers. "It was the collective effort by scientists across a wide range of disciplines and institutions that gathered all the evidence to assemble the puzzle. We hope it inspires other studies," Yu added. Anyone can contribute to science Photo databases built by ordinary people going outside with a smartphone can become serious scientific data when paired with the right experiments. "You can't say, 'No, the experiment is true,' and just ignore citizen science," Yu said. "You've got to put them together." The next time you photograph a wildflower and upload it to iNaturalist or a similar app like EarthSnap, you may be contributing to exactly that kind of discovery. The science of how life adapts is hiding in plain sight, and the public has been collecting the evidence all along. The study is published in the journal Cell. -- - Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

Integrating 'citizen science' with experimental data helps uncover how plants adapt | Newswise

AMES, Iowa - In its native habitat, switchgrass flowered earlier when growing farther north. In experiments with diverse genetic samples, it flowered earlier in the south. The discrepancy wasn't a welcome sight for a research team studying how prairie grasses respond in different environments, but resolving the apparent conflict led the scientists to draw better conclusions, showing the potential value of large public data sets collected in natural growing conditions. The study published late last month in the high-profile, peer-reviewed scientific journal Cell, "Harnessing citizen science to contextualize adaptation mechanism discovery," integrated trends culled from AI-powered scans of tens of thousands of online photos of perennial grasses with findings from two years of growing switchgrass at research sites across the Midwest and Gulf regions as well as a detailed molecular characterization of three underlying genes involved in switchgrass flowering. Led in part by Iowa State University agronomy professor Jianming Yu, the research team identified the genetic basis for adaptative responses that help explain the contradictory flowering-time trends. But the framework - wringing useful insight from "citizen science," in this case an online cache of photos mostly from iNaturalist - is as notable as the findings, said Yu, the Pioneer Hi-Bred Distinguished Chair in Maize Breeding and director of the Raymond F. Baker Center for Plant Breeding. "With this study, we have connected our quantitative genetic and genomic research with ecology, evolution and adaptation over a large-scale landscape. The beauty is we're bridging them together so we can see the whole picture," he said. Conflicting data Researchers built an AI tool to screen nearly 44,000 photos of warm-season grasses with time and location data, yielding about 5,000 observations of flowering switchgrass, big and little bluestem, and indiangrass. In each of the four species, the average flowering time was earlier in the north than the south. Focusing on switchgrass, the most studied of the four grasses, researchers analyzed data from genetic mapping populations of switchgrass to identify a gene network associated with flowering time. Studying a diversity panel collected as samples from wild-grown switchgrass, they found three haplotypes - combinations of variants of the three underlying genes linked to flowering. Each haplotype was primarily found in geographic clusters, including a variant specific to the Midwest and one common in Gulf Coast states. Switchgrass samples containing haplotypes associated with the Midwest and Gulf regions were grown at 10 research gardens for two years, flowering on average 2.3 days later for every degree of latitude farther north - opposite of the data from native habitats. "We had to wrap our minds around that," Yu said. Adaptation at work Added context pointed a way toward a solution. Analyzing the expected flowering time of the diversity panel with a model that included genetic and environmental data showed the temperature from April 25 to May 5 had the strongest correlation with flowering time. Warm weather during that period sped up flowering by 3.4 days for each degree Celsius. But the switchgrass haplotype common in the southern Gulf region, referred to in the paper as H1, tended to flower 45 days later in all instances than the Midwestern haplotype, H2. And H2 flowering was more sensitive to temperature during the critical time in late April and early May, the researchers found. The differences between H1 and H2 make sense for their respective geographies, Yu said. In the north, H2 sprouts flowers earlier because the risk of extreme heat in the summer is lower, but temperatures can get cold in the fall. There's an advantage to flowering earlier so switchgrass can turn its attention to preparing for the winter. Farther south, H1's delayed flowering helps it avoid reproducing during the height of summer, and holding off until late summer poses less risk because fall temperatures are typically more moderate than in the north. "In their native conditions, both haplotypes are doing the things that they need to do to survive and thrive," Yu said. "In the north, they flower earlier because winter is coming. But in the south, there's no rush because summer is so hot and the fall is mild." A powerful pairing Yu said the work shows the effectiveness of pairing controlled research and natural data sets, especially in studying how plants adapt in different environments - a concept also known as phenotypic plasticity. Without considering the public database of photos, researchers wouldn't have spotted the flowering adaptation in native habitats. Without studying genotyped plants, they wouldn't have been able to understand it. "Our study highlights the power of combining citizen science observations with designed experiments to uncover mechanisms of adaptation across spatiotemporal scales," wrote the study's 27 co-authors, including two scientists from the U.S. Department of Agriculture - senior author Xianran Li and first author Laura Tibbs-Cortes - with a history at Iowa State, Li as a research associate professor and Tibbs-Cortes as a doctoral student. "It was the collective effort by scientists across a wide range of disciplines and institutions, led by the senior author Li, that gathered all the evidence to assemble the puzzle. We hope it inspires other studies," Yu said. While relevant publicly collected data isn't always available, it should be integrated with plant experiment data when it is, Yu said. "You can't say, 'No, the experiment is true,' and just ignore citizen science," he said. "You've got to put them together."