Northern Suburbs Branch, 18 September 2024
Joshua Newton began by explaining that any DNA left in the environment, such as hair cells, skin cells, faeces, urine, etc., is referred to as eDNA. When collected and analysed, eDNA allows us to identify and monitor animals without actually seeing them, making it a promising new tool for conservation and ecological research. The technique started with researchers looking for material in ice cores and sediments and then progressed to the aqueous environment.
Now, the technique can be used in the terrestrial environment, as demonstrated by Josh’s Serventy Memorial Prize-winning project of sampling tree hollows (using a paint roller purchased from Bunnings) to collect material for metabarcoding.
One of the project’s findings verified the expected—trees in our national parks contain far greater biodiversity than our urban trees. It also revealed that 80% of the hollows sampled in Kings Park and Bold Park contained Rainbow Lorikeets but no other birds.
Josh admitted there are still many challenges and knowledge gaps to be addressed, but some of the benefits of using eDNA include monitoring rare and protected species, strengthening conventional biodiversity surveys, sampling complex environments, detecting invasive species, and the emerging study of population genetics, where nuclear DNA, not mitochondrial DNA, is required.
eDNA is proving useful in studying the pollination of our native plants. Results show that plants are visited by many more insects and birds than traditional visual sightings have recorded.
For example, eDNA metabarcoding identified 40 species compared with the visual sighting of only 14 species on plants at Helena and Aurora Ranges.
However, more research is needed to determine whether all visitors are pollinators or just incidental visitors. Josh then addressed some of his more recent and current research.
While researchers in Denmark and the USA have captured air samples to analyse, at least two problems remain: how far had the eDNA material travelled, and where from?
Josh solved these problems by selecting two sites, Karakamia Wildlife Sanctuary and Perth Zoo, where the animal population was well known and where nature could provide a trap that was located a known distance from at least some of the animals. The trap was the ubiquitous spider web!
Josh listed the benefits of using spider webs, including that they are widespread, powerful biofilters (sticky traps), span ecosystems, require minimal effort, require no direct interaction, and are non-invasive (for vertebrates).
eDNA from 16 mammals, 14 birds, one reptile, and one amphibian was captured at the Karakamia site. Because the sanctuary is fenced, the eDNA from a fox must have travelled at least 250 metres, while the domestic animals that were detected were at least 800 metres away. As expected, the zoo delivered a larger array of eDNA, with 33 mammals, 21 birds, five reptiles, and two amphibians detected. The giraffe’s maximum distance measured was 200 metres.
These results provided answers to how far eDNA can travel, but the question of how long eDNA survives after being shed remains unanswered.
Don Poynton
All images by Josh Newton