18 March 2026
The cactus on your windowsill may grow slowly,but new research shows that cacti are surprisingly fast at creating new species.
Biologists have long thought that pollinators and specialised flowers drive the formation of new plant species. But scientists at the University of Reading found that in cacti, the secret lies in how quickly flowers change shape, rather than how big the flowers grow or which animal pollinates them.
Researchers studied flower length data for more than 750 cactus species, covering a 185-fold range in size from just 2mm to 37cm. Despite this variation, flower length had almost no relationship with how fast a species split into new ones. Instead, species whose flowers were evolving most rapidly were also the most likely to branch into new species, an effect that held across both recent and deep evolutionary history.
Their study, published today(Wednesday, 18 March) in Biology Letters, challenges ideas going back to Charles Darwin, who studied orchids and suggested that specialised flower forms drove the creation of new plant species.
Jamie Thompson, lead author at the University of Reading, said: "People may think of cacti as tough, slow-growing plants, but our research shows that the cactus family is one of the fastest-evolving plant groups on Earth. Knowing how fast cacti evolve reveals that deserts, often seen as harsh and unchanging, are actually hotbeds of rapid natural change.
"We expected cacti with longer, more specialised flowers to be the ones creating the most new species. Instead, flower size made almost no difference. What matters is how quickly flowers change shape. Cacti whose flowers evolve rapidly are far more likely to split into new species than those whose flowers stay the same, however elaborate they are.
“This result has real implications for conservation. Since flower evolution has helped generate cactus species over millions of years, evolutionary pace should become part of conservation efforts. Although being able to rapidly evolve does not guarantee resilience, especially as the planet is changing faster than most cacti can keep up, it could help predict which species need the most help. Rather than searching for a single trait that predicts which cacti are most at risk, conservationists may need to look at how fast a species is evolving instead."
Mapping the cactus family tree
The cactus family contains around 1,850 species and is one of the fastest-expanding plant groups on Earth, spreading across the Americas over the past 20 to 35 million years.
This research was made possible by anew Open Access database calledCactEcoDB, created by lead author Jamie Thompsonand developed in collaboration with ten coauthors from three continents, including six from the University of Reading. Published this month in Nature Scientific Data, it brings together seven years of work compiling cactus traits, habitats, and evolutionary relationships. With nearly a third of cacti threatened with extinction, the database provides a shared resource for scientists worldwide, to study their biodiversity, conservation and future under climate change,for the first time.
Dr Jamie Thompson and Professor Chris Venditti are available for interview. Contact the University of Reading Press Office on 0118 378 5757 or pressoffice@reading.ac.uk.
Thompson, J. B. & Venditti, C. (2026). Faster speciating cacti have faster evolving flowers. Biology Letters. 10.1098/rsbl.2025.0834
ScientificData study: Thompson, J. B., Martinez, C., Avaria-Llautureo, J., Ramírez-Barahona, S., Manzanarez-Villasana, G., Culham, A., Gdaniec, A., Ryan, G., Venditti, C., Keeling, G., & Priest, N. K. (2026). CactEcoDB: Trait, spatial, environmental, phylogenetic and diversification data for the cactus family. Scientific Data. https://doi.org/10.1038/s41597-026-06936-7
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