Environmental DNA shows some frog species bouncing back from fungus

A study utilizing environmental DNA (eDNA) has revealed encouraging signs of recovery for two endangered frog species in Queensland's World Heritage Daintree Rainforest. Researchers from James Cook University (JCU) collected water samples from 11 sites, searching for the eDNA of three species severely impacted by chytrid fungus outbreaks in the 1980s and 1990s. The findings indicate that the waterfall frog (Litoria nannotis) and the Australian lace-lid frog (L. dayi) have rebounded to the extent that they were detected in new territories.

"That was a nice surprise because they have recovered better than we, or the scientists, originally thought they had recovered," said Cecilia Villacorta-Rath, senior research officer with Tropwater JCU. The study, published in the journal Conservation Science and Practice, highlights the effectiveness of eDNA analysis, which allows researchers to monitor elusive aquatic species more easily. Frogs were chosen for the study due to their aquatic lifestyle, which facilitates DNA detection in water samples.

However, the research also cast a shadow over the recovery prospects of the critically endangered armoured mistfrog (Litoria lorica). This species, believed to exist in only one remaining population, showed little sign of recovery. Sampling between October 2019 and January 2020 detected the armoured mistfrog at only one of the 11 surveyed sites, indicating its continued struggle for survival.

Chytrid fungus (Batrachochytrium dendrobatidis) has been a devastating force for amphibians globally, causing mass die-offs and leading to the extinction of at least four species in Australia. The fungus attacks the keratin in frogs' skin, disrupting vital functions and often proving fatal. Laura Grogan, a senior lecturer in wildlife science at the University of Queensland, noted that recovery responses to the fungus vary significantly among species. Factors such as individual species' susceptibility, infection load in the environment, development of resistance, behavioral changes, and even alterations to the fungus itself can influence recovery rates.

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That was a nice surprise because they have recovered better than we, or the scientists, originally thought they had recovered.