Exotic species invade us every day, causing endemic animals and plants to decline and often become extinct, over time. The newer techniques of using DNA in water to specify what is resident in a river or stream is becoming more and more efficient. The
environmental DNA fragments found in Japanese rivers too often include the related Chinese giant salamander, instead of the endemic Japanese species. These two hybridise, so it is vital to eliminate the invasive species. Andrias japonicus was found here at 25 different sites within central Japan’s Katsura River catchment basin, presumably including the Rivers ÅŒi and Hozu, in the form of its mitochondrial DNA.
The mtDNA of Andrias davidiana should not have been in the Japanese islands, but it was indeed detected at 9 sites in Kyoto Province, some beyond the area which it is known to be colonising. The time and effort required to sample by capture techniques and survey is way beyond the resources of some research. This latest technique was able to be carried out by Sou Fukumoto, Atushi Ushimaru and Toshifumi Minamoto of Kobe and Kyoto Universities and the Kyoto Institute for Humanity and Nature three times during the autumn and winter seasons. More sampling is likely to be added to this to continue monitoring the advance of the invasive species and the state of the native population.
Use of the trapping survey in combination with such environmental DNA sampling will in future simplify and make more accurate many surveys of all aquatic species. We can even hope for new species to be discovered, as the accuracy of mtDNA diagnosis is beyond doubt and likely to become even more convenient as it develops further. Skin or excreta are thought to be the main salamander components of the DNA found. Amplified as at present, using what is known as the PCR (real-time polymerase chain reaction) all occupied habitat can be identified and even the specific niche can be informed upon, given the total distribution records. Only 4 litres of water are required at a site, from which the DNA is concentrated. We can be reasonably certain that the sites at which no DNA was found contained no salamanders, or they were situated at a great distance upriver. Most positive results for locations were in upper reaches of streams.
The Journal of Applied Ecology publish the paper as A basin-scale application of environmental DNA assessment for rare endemic species and closely related exotic species in rivers: a case study of giant salamanders in Japan. Publication is very appropriate for the A japonicus as it has long been a much revered creature for ancient Japanese and a designated natural
monument! Both species are truly giant, especially compared with this North American coastal giant salamander, Dicamptodon tenebrosus This is also a Japanese first, as a research study that uses DNA in this manner for a wide geographical area