Cacti are rewriting Darwin's playbook on how new plant species emerge

Turns out, cacti are way faster at evolving new species than anyone thought. Seriously, these spiky desert dwellers are challenging a theory Charles Darwin himself laid out about how evolution works.

For ages, scientists figured that fancy flowers and their specific pollinators were the big drivers behind new plant species. Think of a unique flower shape perfectly matched to a certain bee. But researchers at the University of Reading just found something different with cacti.

They discovered that the speed at which a cactus flower's shape changes over time is the real secret. It's not about how big the flower is, or even which animal pollinates it. That's pretty wild.

The team looked at over 750 cactus species. Their flowers go from tiny 2-millimeter buds to massive 37-centimeter blooms. Yet, all that size difference didn't matter much. The cacti with the fastest-changing flowers were the ones most likely to split off into new species. This held true for both recent and ancient cactus evolution.

This study, published in Biology Letters, directly pushes back on ideas that started with Darwin. He believed specialized flower forms, like the ones he saw in orchids, were key to creating new plant species.

Quick Change Artists

Jamie Thompson, who led the research, pointed out that cacti are actually one of the fastest-evolving plant groups on Earth. It's a reminder that deserts, which seem so still and unchanging, are actually hotbeds for rapid natural shifts.

Thompson admitted they expected the cacti with longer, more specialized flowers to be the ones cranking out new species. But flower size barely registered. It's all about how quickly those flower shapes morph. Cacti whose flowers change fast are way more likely to branch into new species than those whose flowers stay the same, no matter how complex they are.

This matters for saving species, too. Since flower evolution has been creating cactus species for millions of years, the speed of that evolution should be part of how we protect them. While fast evolution isn't a silver bullet in our rapidly changing world, it could help predict which species need the most urgent help. Instead of just looking for a single trait, conservationists might need to consider how fast a species is evolving.

Mapping the Spiky Family Tree

The cactus family has about 1,850 known species and it's one of the fastest-growing plant groups around. They've spread across the Americas over the last 20 to 35 million years. To figure this all out, the study used a clever new open-access database called CactEcoDB.

Jamie Thompson and ten other scientists from three continents built this database over seven years. It pulls together tons of info on cactus traits, where they live, and how they're related. With nearly a third of all cacti facing extinction, this database gives scientists worldwide a shared tool. It helps them study cactus diversity and figure out how to protect them as our climate keeps changing.