Dr Mieke Van Der Heyde1, Marina E. de Oliveria1, Paul Nevill1, Angus Lawrie1, Mahsa Seyedeh Mousavi-Derazmahalleh1
1Trace and Environmental DNA Laboratory, School of Molecular and Life Sciences, Curtin University, Kent Street, Bentley, Australia
Biography:
TBC
Abstract:
Terrestrial ecosystems in arid and semi-arid regions are difficult to monitor because biodiversity is often patchily distributed, cryptic, and poorly detected by methods developed for other habitat types. Environmental DNA (eDNA) offers a promising alternative, but its spatial resolution in terrestrial systems remains poorly understood. Here, we tested whether fine-scale ecological change (up to 1 km) across habitat boundaries (natural and highly disturbed) can be detected using different terrestrial eDNA substrates. We collected 360 samples in two contrasting Australian ecosystems, Dryandra Woodland National Park (Western Australia) and Roxby Downs (South Australia), using soil, passive air filters, and surface rollers. We used three metabarcoding assays (16S, 18S and COI) amplifying taxa across the tree of life and employed a taxonomic-free analysis framework. Overlap among substrates was low (2–7%), indicating strong methodological complementarity. At the extreme ends of the gradient, all substrates detected significant differences in community composition between natural and disturbed habitats. However, piecewise beta models revealed clear substrate-specific responses across ecotones: soil and rollers showed strong step changes at habitat boundaries, whereas passive air filters showed no significant ecotonal response. These results suggest that soil and surface-derived eDNA capture more localised community signals, while airborne eDNA integrates biodiversity over broader spatial scales. Our findings demonstrate that terrestrial eDNA can detect fine-scale community turnover in arid and semi-arid ecosystems, but that ecological inference depends strongly on substrate choice.