Mosquito iDNA reflects fine scale composition of tropical fauna

Changes in fire regimes and the introduction of invasive species are negatively impacting Northern Australia's biota, highlighting the need for reliable biodiversity monitoring data. Here we used mosquito-ingested DNA (iDNA) to detect birds and mammals within Kakadu National Park. Six sites were sampled on two occasions (wet and dry season), with three traps deployed for two consecutive nights of sampling at each site. Mosquitoes were processed in bulk samples per trap ranging from 31 to 1987 mosquitoes. Extracted DNA was amplified using primers targeting vertebrates (12SV5), mammals (16SMam1/2) and birds (Aves01) with iDNA-derived richness and composition measured. A total of 50 avian and 19 mammalian taxa were detected, including threatened species such as the white-throated grasswren (Amytornis woodwardi) and the ghost bat (Macroderma gigas), along with difficult-to-monitor groups such as small-bodied and arboreal mammals. Community composition was shown to be distinct between sampling events, and avian richness was higher during the dry season. Importantly for the management of the park, our findings suggest that fire regimes modified both bird and mammal communities during the dry season, with vegetation structure being correlated with avian and mammalian community composition during the wet season. This study highlights the capacity for iDNA metabarcoding to provide fine-scale ecologically relevant information within a large, dynamic and difficult-to-access landscape.