Viral diversity, ecological interconnectedness, and the identification of mammalian chuviruses in Australian microbats

Microbats are a large and ecologically important group of Australian mammalian fauna. However, their RNA virome diversity, as well as its ecological and evolutionary significance, has received limited study. We applied a metatranscriptomic approach to reveal more of the diversity of RNA viruses present in faeces from different microbat species in New South Wales and South Australia, including the critically endangered Southern bent-wing bat (Miniopterus schreibersii bassanii) from the Naracoorte bat maternity caves in South Australia. The data generated revealed a high diversity of RNA viruses, including 51 likely mammalian-associated viruses classified into ten taxonomic groups, including the Coronaviridae, Hepeviridae and Chuviridae. Notably, we identified a mammalian-specific lineage of chuviruses associated with bats in Australia and of bats and rodents in China, strongly suggesting that viruses of this family have established sustained transmission cycles in mammals as well as invertebrates. Our results also revealed widespread viral connectivity among alphacoronaviruses across multiple microbat species in mainland Australia and Christmas Island, indicative of long distance viral movement. High viral diversity and virus co-circulation was observed within the Southern bent-wing bat population of the Naracoorte caves, suggesting complex population dynamics that might facilitate virus maintenance and transmission. Overall, these findings highlight the role of Australian microbats as viral reservoirs, including the presence of viruses not previously associated with sustained mammalian transmission.