Development of a 16S metabarcoding assay for the environmental DNA (eDNA) detection of aquatic reptiles across northern Australia

Abstract

A severe lack of distribution data for aquatic reptiles in northern Australia leaves many taxa vulnerable to extirpation and extinction. Environmental DNA (eDNA) technologies offer sensitive and non-invasive genetic alternatives to trapping and visual surveys and are increasingly employed for the detection of aquatic and semi-aquatic reptiles. However, at present, these studies have largely applied species-specific primers which do not provide a cost-effective avenue for the simultaneous detection of multiple reptilian taxa. Here, we present a 16S rRNA metabarcoding assay for the broad detection of aquatic and semi-aquatic reptile species. This assay is tested on water samples collected at multiple sampling sites at two tropical locations: 12 marine/estuarine sites in Roebuck Bay, Western Australia, and 4 estuarine sites in Cooktown, Queensland, Australia. A total of nine reptile taxa were detected from 10 of the 16 sampled sites, including marine and freshwater turtles, aquatic and semi-aquatic/terrestrial snakes, and terrestrial skinks. However, inconsistencies in the detection of previously observed aquatic reptiles at our sampled sites, such as saltwater crocodile and sea snakes, indicates that further research is required to assess the reliability, strengths and limitations of eDNA methods for aquatic reptile detection before it can be integrated as a broad-scale bioassessment tool.