A hungry leaf (Image: Alexander R. Schmidt, University of Göttingen)

It lurked in wait for unsuspecting prey on the swampy Baltic coastline 35–47 million years ago. Now the first fossilised specimens of a carnivorous plant are helping scientists probe the organism’s early evolution and its Eocene habitat.

Researchers from the University of Göttingen in Germany found the fossil of two leaves from the plant in the Jantarny amber mine near Kaliningrad, Russia. It seems to be related to plants from the Roridulaceae family, which catch their prey using long, sticky hairs.

“We were all so excited when we discovered it because it’s very beautiful and striking,” says lead researcher Eva-Maria Sadowski. “It’s amazing to look at something so old, yet so well preserved.”


The fossils were a long way from where this family is endemic: South Africa. “It was surprising to find the fossils in Europe. It suggests they were probably more widely distributed than initially thought and later restricted to a few places,” says co-author Alexander Schmidt.

Supercontinent

This plant family is thought to have originated in Africa and became isolated there after the Gondwana supercontinent – comprising modern-day Africa, South America, Madagascar, India, Australia, the Middle East and Antarctica – broke apart about 180 million years ago.

The leaves have hairs that could have been used to capture prey. With only two leaves preserved in the amber, it’s not yet possible to know what the entire plant looked like and what its diet could have been, but the plant family today catches a wide range of arthropods.

The Roridulaceae genus Roridula is a quirk of botanical carnivory, as the plants depend on relationships with other organisms to successfully digest their prey. They trap prey using sticky hairs on their leaves, but depend on a symbiotic species of capsid bug to digest them and then consume their droppings instead. One bug’s demise is another’s gain.

“It really is remarkable to consider that this genus was once so much more widespread, and this seems to indicate that it really is a relic today, hanging on against extinction,” says Martin Cheek, a senior botanist at Kew Gardens in London.

“It gives us a great insight into how much things have changed. It is inconceivable today that oaks and Roridula should co-occur in nature, but obviously they did,” Cheek says. “The specimen is so well preserved that it is as if someone had nipped back in a time machine into the Eocene and got it. Who knows what other revelations are on their way through this fossil source?”

Eocene forest

It’s rare to find plant remains in amber that are well-preserved enough to be studied in fine detail.

Most fossils found in amber are insect remains because they tend to be quite small, whereas it’s harder to preserve large plant remains, says Schmidt.

“If we look at amber from many localities and many geological time horizons, we get unique access to groups of organism that would otherwise be hardly preserved,” says Schmidt.

While it’s difficult to tell from a single plant what the environment would have been like 35 million or more years ago, the study describes coastal areas with mixed forests of carnivorous and flowering plants with open, patchy habitats. The carnivorous plant would have been able to survive in the carbonate-free, nutrient-poor soil.

The carnivorous-plant fossils therefore provide important clues for reconstructing the habitat, but many more pieces are needed to get a full picture of what this Baltic Eocene forest looked like.

Journal reference: PNAS, DOI: 10.1073/pnas.1414777111