A secret life at Secret Rocks - Unexpected regeneration after fire

Alana McClelland’s fieldwork uncovered three species of lerps and more than 10 species of wasps and flies during her visit in September 2021. Image: Alana McClelland.

Tiny insects that live on Eucalyptus leaves have been forced to travel vast distances or change what they eat to survive, after bushfires destroyed their habitat.

University of Adelaide scientists surveying bushfire-impacted areas at Secret Rocks on South Australia’s Eyre Peninsula are surprised by the resilience of psyllid insects and their leaf-dwelling nymphs who live in sugary huts – known as lerps.

“Lerps are rarely found on fresh, soft leaves, such as new growth after fire,” said School of Biological Sciences PhD candidate Alana McClelland.

“The immature insects which feed on the trees generally don’t like the chemical composition of the young leaves, so it’s a huge surprise that they’re surviving by adjusting their diet.”

Ants tending to lerps on a Eucalyptus leaf, by Donald Hobern (CC BY 2.0)

Ants tending to lerps on a Eucalyptus leaf, by Donald Hobern (CC BY 2.0)

The discovery was made on the property of University of Adelaide adjunct lecturer Dr John Read, who lives at Secret Rocks, about 45 minutes east of Kimba.

Ms McClelland visited Dr Read’s property for fieldwork with her colleagues nine months after the bushfires of summer 2019/20. She said that regeneration of this population of lerps was "so unexpected”.

"A psyllid can’t travel very far, so it was really surprising to see them as the surroundings were burnt as far as the eye could see,” she said.

“Did they somehow survive the fires? And did adults travel ridiculous distances to find the only leaves they could lay eggs on,” she said.

“Equally astounding was the adaptability of them to be surviving on this fresh new growth, of which there wasn’t much.”

Ms McClelland collected some of the lerps for her research, as tiny parasitic wasps use the lerp babies as hosts.

“Expecting zero chance of the lerps being parasitised by these wasps, I took them back to the lab and cared for them in the hopes that wasps would emerge,” she said.

“And they did! This evidence of rapid population recovery was so heartening.

“The presence of these insects increases the chance of re-establishment of populations of larger insects, birds and reptiles, and while we couldn’t see evidence of this yet, I was already planning another trip back to Secret Rocks a year later to see what was happening.”

Fast forward 12 months to late 2021 and Ms McClelland was back at Secret Rocks.

“The difference was incredible - a year of good rains and thankfully, a fire free summer, had incredible results,”

“Lerps were less abundant, but this is a good thing, as it indicates the presence of a more diverse range of other insects and birds which were feeding on them.

Ms McClelland’s fieldwork uncovered three species of lerps and more than 10 species of wasps and flies during her visit. The wildflowers were also out and had attracted populations of pollinators.

It’s now two years since the devastating bushfires of summer 2019/20 both in South Australia and on the eastern coast of Australia. We see evidence of the resilience and fortitude of the environment, but also the people who are fighting to regenerate it.

One of those people is ecologist Dr Read - almost half of his 26,000ha property was destroyed by fire.

“It’s great seeing fairy wrens, babblers and even little Weebils that feed exclusively in eucalyptus canopies, living back around our house again, and the tracks of Mitchell’s hopping mice and knob-tailed geckoes are crisscrossing the burnt sandhills” said Dr Read.

Dr Read and his fellow biologist wife Dr Katherine Moseby have even taken advantage of the fire to fence kangaroos and goats from 3900ha of land to enable the regrowth to flourish. It's helping restore the local ecosystem - from lerps and wasps all the way to Malleefowl and reintroduced bandicoots.

“When nurtured and protected by scientists, naturalists, landowners, and passionate communities, nature can recover, and I feel far more positive about the regeneration of fire damaged areas after being lucky enough to see the flourishing secret life at Secret Rocks,” said Ms McClelland. 

Sciences research in focus

Alana Delaine

Alana McClelland is an early career scientist who studies parasitic wasps. She studies Psyllaephagus, a problematic and largely undescribed genus of tiny wasps which lay their eggs inside the nymphs, or babies, of a group of insects called lerps that live and feed on the leaves of Eucalypt trees. Psyllaephagus control the lerp populations and prevent outbreaks which would otherwise defoliate and kill the trees.

Follow Alana on Twitter via @entoandbento.

Tagged in Research, Engagement and Industry, School of Biological Sciences, Environment Institute, Environmental Science, Evolutionary Biology, Ecology