Prof. Lori Lach1, Dr Samantha Tol1,2, Mr Carl Shuetrim1, Dr Peter Yeeles1, Dr Cecilia Villacorta-Rath1,2

1James Cook University, Centre for Tropical Biosecurity, Cairns, Australia, 2James Cook University, TropWATER, Cairns and Townsville, Australia

Biography:

Professor Lach is internationally recognised for her 20+ years of ant ecology research, particularly her work on invasive ants. Her research encompasses the ecology, impact, detection, and control of invasive species. She co-leads several projects researching new technology to improve invasive ant detection. She is the Director of the Centre for Tropical Biosecurity at James Cook University. She was honored to be the recipient of the Ian Mackerras Medal in 2022.

Abstract:

Yellow crazy ants (Anoplolepis gracilipes) are a widespread and environmentally disruptive invasive species that, as with any ant species, can be difficult to detect when it occurs in small, incipient colonies. Targeted environmental DNA (eDNA) has a history of use for the detection of aquatic organisms, but its application for the detection of terrestrial organisms is much less explored. Following development of an assay and field validation, we conducted field and laboratory tests to determine the effect of rainfall on eDNA deposited by live and dead yellow crazy ants. Simulated rainfall experiments over soil that had been exposed to live yellow crazy ants revealed that yellow crazy ant eDNA concentration initially increased with increasing flushes, likely as water caused eDNA to unbind from the soil, before decreasing with subsequent flushes. Once in the water, yellow crazy ant eDNA degraded rapidly. Simulated rainfall over soil exposed to dead yellow crazy ants for 28 days yielded consistent positive detections even after 20 flushes, representing 4 mm rainfall events each, over two days. Sampling from creeks and rivers downstream of known infestations revealed a strong effect of recent rainfall on detection. Targeted environmental DNA technology shows promise as a tool for detecting terrestrial insects and more testing will elucidate the contexts in which it is most sensitive.