Extinct sawfly reveals how insects have co-evolved with plants

A team of Australian researchers has identified a new species of extinct sawfly from an exceptionally well-preserved fossil found in central New South Wales (NSW).

This fossil, estimated to be between 11 and 16 million years old from the Miocene Period, is the first of its kind discovered in Australia and only the second globally. 

The find was made in 2018 by a group of paleontologists exploring McGraths Flat, a fossil-rich site that has since yielded numerous other detailed fossils.

What are sawflies?

Despite their name, sawflies belong to the wasp family rather than the fly family. In Australia, spitfires are the most familiar group of sawflies. 

The name “sawfly” comes from their saw-like ovipositor, which they use to lay eggs. While they might be mistaken for flies, they differ due to their lack of a characteristic “wasp waist.”

Naming new sawfly species

With approval from the Mudgee Local Aboriginal Land Council, the research team named the new species Baladi warru using Wiradjuri words. “Baladi” translates to “saw” and “warru” means “wasp,” a name that honors the Traditional Owners of the land where the fossil was discovered.

The research team, which included scientists from CSIRO, the University of Canberra, the Australian Museum, and the Queensland Museum, studied the fossil’s wing venation and other preserved features. 

The analysis allowed them to determine its place in the scientific classification of sawflies, describing it as a new species. 

“We looked at the fossil and its morphology and then put this information together with molecular and morphological data from a wide sample of current sawfly species. This helped us decipher the fossil’s placement in the sawfly tree of life,” explained lead author Juanita Rodriguez, a research scientist at CSIRO.

Tracing sawfly origins

The study of this fossil provided critical insights into the evolutionary history of sawflies. Using the fossil’s age and position within the broader sawfly lineage, the researchers concluded that sawflies originated during the Cretaceous Period, about 100 million years ago. 

This timeline indicates that their ancient ancestors lived on the supercontinent Gondwana, which eventually split into present-day continents. As Gondwana broke apart, sawflies spread across regions that would become Australia and South America.

Pollen reveals ancient plant interactions

The fossilized sawfly also revealed details about ancient ecosystems. The researchers identified pollen grains on the head of the sawfly, indicating it had visited a flowering Quintinia plant before fossilization. 

This evidence allowed the team to reconstruct interactions between species in the Miocene environment of McGraths Flat.

“When we examined the fossil, we identified pollen grains on the sawfly’s head which revealed it had visited a flowering Quintinia plant. This helped our team trace complex species interactions in the palaeoenvironment of McGraths Flat,” Rodriguez said.

Sawfly diet and adaptations

This fossil discovery also sheds light on the feeding habits and adaptability of ancient sawflies. 

“This find has helped us in understanding the incredible ability of sawflies to feed on toxic plants,” said co-author Michael Frese, a paleontologist at the University of Canberra. 

“They eat the leaves of Myrtaceae – a family of woody plants that includes eucalypts – because they have mouthparts with which they can separate toxic oils or a chemical detoxification system inside their gut when feeding on myrtaceous leaves. This enables the larvae, sometimes called spitfires, to use the oils as a defensive weapon.”

Linking past and present ecosystems

Though Baladi warru has been extinct for millions of years, its discovery provides valuable insights into the evolutionary history of sawflies and their role as pollinators. 

This ancient species helps explain how sawflies adapted to various environments and dietary sources over time, informing current understandings of their distribution across Australia and the Americas.

“In terms of the bigger picture, our work is helping researchers make sense of their current distribution across Australia and the Americas,” said Frese. 

“Although this particular species, Baladi warru, has been extinct for millions of years, it provides information on native pollinators so we can understand their evolution and impact in the present.”

The study is published in the journal Systematic Entomology.

.

—–

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.

—–