Detecting frogs through invertebrate-derived DNA
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Green Tree Frog (Litoria caerulea) and mosquitos.
Image: Lachlan Pettit© Lachlan Pettit
Species observations and occurrence data inform the whole conservation process; in order to effectively conserve biodiversity, an understanding of where species live is needed. However, the collection of such data is often difficult for some species – particularly those that are threatened, secretive, or otherwise difficult to detect.
Parasitic invertebrates, which are essentially everywhere, can be easily collected and can carry information about their more elusive vertebrate host species. Parasites that have recently fed have DNA from their host within their gut. These pre-collected DNA samples can do away with the need to directly observe those elusive hosts during biological surveys.
By sequencing host DNA provided by invertebrate parasites, relatively easy detection of their hosts can be achieved – even of those species typically most difficult to observe. This invertebrate-derived DNA, or iDNA, is a relatively new survey method for vertebrates, but it has been very effective for the detection of rare and cryptic mammals.
Despite many reptiles and amphibians needing urgent conservation attention, the handful of detections of any species in either group through iDNA have been incidental. The Australian Museum herpetology team is at the forefront of Herpetological iDNA surveys. We have been developing an iDNA survey method that targets frogs, which generally are highly threatened, can be difficult to detect, and are the preferred hosts of a range of blood-feeding parasites.
Barrington Tops Tree Frog (Litoria barringtonensis) with blood-sucking frog fly (Sycorax sp.) NSW, Australia.
Image: Jodi Rowley© Australian Museum
Our preliminary work has demonstrated that, by tweaking the methods of previous (mostly mammal-focused) iDNA studies, frog parasites can be used to increase the detectability of multiple frog species. iDNA can be used in targeted surveys of frog diversity and, particularly if used to complement traditional survey methods, could result in shorter field periods necessary to achieve a survey’s goals. iDNA holds promise in the search for rare species, including those that are missing, feared extinct, and may also be useful in biosecurity, detecting invasive species.
Tim Cutajar is leading our work to refine this novel survey method through improved field and lab techniques as well as a better understanding of frog-parasite interactions.
Whirring Tree Frog (Litoria revelata) with blood-sucking frog flies and a mosquito, NSW, Australia.
Image: Jodi Rowley© Jodi Rowley
