A Novel Landscape Macrogenetics Approach Reveals Conservation Implications of Australia's 2019–2020 Black Summer Wildfires

Jarrod Sopniewski , Rhiannon Schembri, Craig Moritz , Andrew M Baker, Stephane Batista, Stephen C. Donnellan, Mark D.B. Eldridge, Emma L Gray, Ian C Gynther, Greta J Frankham, Harry B Hines, Conrad Hoskin, Michael Mahony, Eugene D Mason, Jane Melville, Nicola J. Mitchell, Madeline Mutton, David Newell, Kate O'Hara, Paul M Oliver, Sally Potter, Jodi J. L. Rowley, Benjamin Scheele, Glenn M. Shea, Joanna Sumner, Renee A. Catullo

Aim
The use of genetic analyses has become ubiquitous in conservation planning and management. Typically, such analyses are employed at the species-level, though as genetic data accrue, it is now possible to consider the genetic composition of multiple species across landscapes. Such macrogenetic perspectives can reveal the potential genetic ramifications of extreme disturbance events, such as the catastrophic Australian ‘Black Summer' wildfires of 2019–2020. Here, we present a framework to examine the potential genetic impacts of this event upon populations of a variety of taxa.

Location
Eastern Australia.

Methods
Using hundreds of samples spanning dozens of frog, mammal and reptile species, we demonstrate a macrogenetic approach for using reduced-representation sequencing data from several species to describe the fine-scale distribution of genetic diversity across a landscape in a robust, comparable manner. We do so using standard population genetics metrics (heterozygosity); though we also propose a novel complementary measure—‘weighted distinctiveness’—to identify important regions of the landscape where narrowly distributed and evolutionarily distinct populations from multiple species reside.

Results
Although variable across the study area, we show that these unprecedented fires generally burned areas where genetic diversity of sampled taxa was higher than that of areas remaining unburned. Additionally, regions harbouring high concentrations of evolutionarily distinct and narrowly distributed species were disproportionately represented in burned regions, with the potential cross-taxonomic adverse effects being greatest in Australia's southeast and central eastern seaboard regions.

Main Conclusions
Our findings suggest that the macrogenetic impacts of the Black Summer wildfires have the potential to have been more severe than initially apparent. Importantly, they also demonstrate how conservation genetics principles often applied at a species level can be expanded to landscapes, whilst accounting for the challenges that arise when aggregating across taxonomic groups, thereby improving our understanding of the overall impacts of large-scale disturbance events.