Conservation macrogenetics reveals the potential hidden consequences of the 2019-2020 Black Summer fires on Australian biodiversity

The use of genetic analyses has become ubiquitous in conservation planning and management as biodiversity is increasingly threatened globally. 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 2019/20. This extensive event severely impacted habitats and fauna across much of eastern Australia – but whether there have been cryptic impacts upon genetically distinct populations, or significant erosion of high diversity populations across species, remains unknown. Here, we present a conservation macrogenetics framework to examine the potential genetic impacts of large-scale disturbances. Using hundreds of samples, spanning dozens of frog, mammal, and reptile species, we first demonstrate how reduced-representation sequencing can be aggregated across species to describe the distribution of genetic diversity across a landscape. We then show that, whilst variable across the study area, these unprecedented fires generally burned in areas where genetic diversity of sampled taxa was higher than areas left unburnt. Additionally, areas with high concentrations of evolutionarily distinct and short-range species were disproportionally represented in burned regions. In particular, potential cross-taxonomic adverse effects were greatest in Australia’s southeast and central eastern seaboard regions. More broadly, our work exhibits how the conservation genetics principles often applied at a species-level can be expanded to landscapes, improving our understanding of the genetic implications of large-scale disturbance events.