Environmental DNA Reveals Habitat Variables Driving Platypus () Distribution Across an Urbanised Landscape.

Freshwater waterways, and species that depend on them, are threatened by urbanisation and the consequences of the urban stream syndrome. In south-east Queensland, Australia, little is known about the impacts of the urban stream syndrome on the platypus (), meaning that populations cannot be adequately managed by conservation practitioners. The aim of this study was to determine how habitat and environmental variables, related to the urban stream syndrome, influenced platypus distribution across this region. We used environmental DNA sampling over a 5-year period (2016-2020) to determine how platypus occurrence (presence or absence) was affected by habitat and the environment. Five scenarios based on key characteristics of the urban stream syndrome were modelled using binomial generalised linear models. The highest-ranked model of platypus occurrence included positive effects of topographic wetness index and coarse organic matter. These findings reflect important waterway connectivity and food resources for platypus, highlighting relationships between platypus, their environment and their tolerance to urban stream threats. For example, platypuses are unlikely to occur in streams where water availability is reduced, and movement will be limited in shallow, dry streams. Therefore, waterway management should focus on water availability and connectivity, especially during drought. Our study can be used to guide management plans for the persistence of platypus and other freshwater species.