As if a giant 6-foot-long and 140 lbs salamander doesn’t have enough to worry about. The critically endangered status of the Chinese Giant salamander, Andrias davidianus,has been due to habitat destruction, overexploitation, spread of diseases and climate change. Critically endangered in the wild, it has now been acknowledged that conservation practices have essentially been inbreeding them into extinction.
These colossal amphibians were once common in rivers across Southeastern China. Back in the day “People didn't want to touch them, didn't want to eat them, didn't want to go near them,”“It was bad luck if you did any of those things, or bad luck if you even saw them,” says Samuel Turvey, a conservation biologist of the Zoological Society of London. Unfortunately, humans got a taste for giant salamander (~$1,500 per salamander) meat in the 1970s and now are only guaranteed finding them within China’s commercial farms. With good intentions farmed individuals have been used to replenish wild populations around China, without prior genetic testing or screening for disease. This in theory is a good idea however the major problem was that most farms were pretty much producing a single lineage, from the Yellow River.
Genetically where do the issues lie? Given its broad distribution, long evolutionary history and poor dispersal capabilities, despite populations from different regions looking the same (known as a cryptic species), they may be actually genetically distinct populations. This is what Turvey and his colleagues were aiming to tease apart, whose details are disclosed in a recent article in Current Biology. To take it back to the farmed releases into the wild, they are introducing one lineage across all native populations. This means that cross breeding the farmed with wild salamanders is basically homogenizing the genetic diversity of the wild populations.
Over ten years the researchers acquired tissue samples from 70-wild caught and 1034 farmed giant salamanders. Analyzing the DNA of the wild specimens it became apparent that they could be separated into five distinct genetic groups which diverged (split from one another) five to 10 million years ago. The mixing of farmed and wild species has led to the hybridization of the species and increased the risk of extirpation the rare wild populations. Since 2008 it was estimated that at least 72,000 salamanders have been released from farms. Recent captures from the tributaries of the Pearl and Yangtze rivers were found to possess the same genetic variation of the farmed Yellow River lineage, but none possessing the indigenous genetic variation.
There are many examples of cryptic species across the planet where morphological differentiation is insufficient to create distinction. Therefore, there needs to be proficient taxonomic and genetic differentiation study before conservation efforts like this are implemented.
For this really interesting publication on Giant Salamander genetics please see:
https://www.cell.com/current-biology/fulltext/S0960-9822(18)30432-9
Fang Yan, Jingcai Lü, Baolin Zhang, Zhiyong Yuan, Haipeng Zhao, Song Huang, Gang Wei, Xue Mi, Dahu Zou, Wei Xu, Shu Chen, Jie Wang, Feng Xie, Minyao Wu, Hanbin Xiao, Zhiqiang Liang, Jieqiong Jin, Shifang Wu, CunShuan Xu, Benjamin Tapley, Samuel T. Turvey, Theodore J. Papenfuss, Andrew A. Cunningham, Robert W. Murphy, Robert W. Murphy, Yaping Zhang, Jing Che. (2018) The Chinese giant salamander exemplifies the hidden extinction of cryptic species. Current Biology. 28, Issue 10, pR590–R592.
