Evolution is commonly thought of as a process that creates new and more complicated traits. But this is not always the case.
On the youngest islands of the Galápagos archipelago, wild tomato plants have adapted to their environment by producing toxins identical to those used by their ancestors millions of years ago.
Tomatoes are a part of the nightshade family, which also includes potatoes and aubergines. Many nightshades, including potatoes, produce alkaloids – bitter toxins that protect the plants against predation.
An international team of researchers were studying these alkaloids because – at high concentrations - they are toxic to humans. The team therefore wanted to get a better grip on how plants make them.
When looking at tomato plants in the Galápagos, the researchers made a surprising discovery. While tomatoes on the older eastern islands produced alkaloids found in modern cultivated tomatoes, the tomato plants on the younger western isles were making unique alkaloids.
Taking a closer look at the chemical make-up of these alkaloids, the researchers discovered that they are identical to the alkaloids that ancestral tomatoes likely synthesised.
Investigating further, they theorised that these ancestral alkaloids might be synthesised via a change in a single enzyme.
To test this, the team synthesised the gene coding for this enzyme and inserted it into tobacco plants. As expected, the tobacco plants quickly began producing ancestral alkaloids.
- Galápagos sea lion guide: how they hunt, and why they're endangered
- Galápagos giant tortoise guide: species facts, where they live and what they eat
The flip to ancestral alkaloids may be an adaptation to the harsher conditions in the western islands. “The plants may be responding to an environment that more closely resembles what their ancestors faced,” lead author of the study, Dr Adam Jozwiak tells BBC Wildlife. But he stresses that more research is needed to support this theory.
While this may look like evolution is ‘going backwards’, what it really shows is the amazing flexibility of evolutionary processes. When the tomatoes found themselves in a new and challenging environment, they evolved an adaptation identical to that of an ancestor that existed millions of years ago.
Finding such a clear example of an organism re-evolving an ancestral trait is rare, and challenges the commonly held view that evolution always means novelty and complexity. Sometimes, it’s worth going back to the good old ways.
Top image: Isla Isabela, Galápagos Islands, Ecuador. Credit: Getty
More wildlife stories from around the world
- Something strange is happening to wild animals on the streets of Chicago
- New DNA study suggests ash trees are evolving to resist deadly dieback disease
- After 54 years of fire, the 'Door to Hell' is finally closing, say scientists
- Coastal wolf found dead in lair on Alaskan island – dissection reveals curious thing that caused it
