Scientists have confirmed two new species of Chinese giant salamander, one of which also takes the title of largest amphibian in the world.

It was previously thought that the Chinese giant salamander (Andrias davidianus) – the largest species of amphibian – was a single species. Now researchers from the Zoological Society of London (ZSL) and London's Natural History Museum, have revealed that there are actually three species, genetically distinct due to being geographically separated: A. davidianus, the South China giant salamander (Andrias sligoi), and an as-yet-unnamed species from Huangshan (the Yellow Mountains) in Eastern China.

The history of Chinese giant salamanders is murky and confusing. The first suggestion of more than one species was put forward nearly 100 years ago, when an unusual salamander from south China was brought to London Zoo in the 1920s.  

“The original description of 'Megalobatrachus' sligoi was done in the days before genetics, which has since provided a powerful alternative tool for understanding the relationships between different animal populations,” lead author Professor Samuel Turvey, of ZSL’s Institute of Zoology, told IFLScience.

“At the time when sligoi was first named, there was also confusion over whether Japanese and Chinese giant salamanders were distinct from each other, so the characters originally used to 'distinguish' sligoi were largely ones that separated Chinese animals from Japanese animals. As such, it was later assumed that sligoi was probably similar to other giant salamanders from China." 

Then in the 1990s, early genetic studies suggested that salamanders from different parts of China were more different than we thought. However, this is where it gets confusing, as Professor Turvey explained, the genetic samples showed differences, but were taken from giant salamanders being bred on farms across China, for the relatively new luxury food market. The market is supplemented by wild-caught animals, mixing the lineages – and leading to a huge drop in wild populations­ – meaning to get a more accurate understanding of the original geographic distribution and genetic variations in giant salamanders they had to look at much older specimens.

Using DNA from 17 historical specimens collected in the early 20^th century, including the original "unusual" salamander that lived at the Zoo for 20 years (and has been residing, preserved, at the Museum ever since), they managed to confirm the new species.

Writing in the journal Ecology and Evolution, the authors revealed that all three species diverged from a common ancestor between 3.1 and 2.4 million years ago, after it had already split from the Japanese giant salamander. Each was then separated by geographic distribution.

“This divergence is close to the known timing of one of the phases of uplift of the Tibetan Plateau, which created distinct mountain regions across southern China,” Turvey told IFLScience. ”This tectonic event would have isolated different populations of giant salamanders and disrupted gene flow, leading to local evolution of distinct species.”

With the new classification, the researchers realized they also had to rethink the title-holder for the world’s largest amphibian.

“The 1.8-meter-long animal caught in the 1920s is the largest known reported giant salamander from China, and it's historically been interpreted as a specimen of A. davidianus because all Chinese animals were thought to represent this species,” Turvey said. “However, this huge animal is actually potentially an individual of sligoi rather than davidianus, based on geographical location (it was caught in southern China).”

Not a lot is known about the as yet undescribed species, as it has only been identified by tissue samples. However, the team thinks it's vital the two new species also get listed as critically endangered alongside A. davidianus, and that both the IUCN and the Chinese government recognize that multiple species of Chinese giant salamander means updating conservation plans accordingly. 

"These results will hopefully lead to individual legal protection for each species and conservation efforts that are tailored to their individual needs," co-author Dr Melissa Marr at the Natural History Museum told IFLScience. "A ‘one-size fits all’ conservation strategy may not be the best approach as there are differences in both the level of human pressure and in land-use practices across the range of these species."

"The next step is to try to locate surviving populations of any of the newly recognized Chinese giant salamander species, and develop effective conservation plans for them before it's too late," said Turvey.