Article Review: Detecting an elusive invasive species: a diagnostic PCR to detect Burmese python in Florida waters and an assessment of persistence of environmental DNA

The Burmese Python is native to Southeast Asia, but in the last 25 years it has been accidentally introduced to southern Florida. This is probably due to people buying them as pets, then abandoning them when they get too big to keep in a house. A full-grown Burmese python averages about 12 feet in length, but can reach almost 20 feet, making them one of the largest snakes in the world. Because they have no native predators in Florida, they are very successful as an invasive species and pose a danger to native species. This includes endangered or locally rare species such as the Florida panther, wood storks, and the American crocodile.

Unfortunately, pythons are very reclusive, so detecting them, catching them, and relocating them is difficult. Recent studies have found that it is possible to detect an aquatic or semi-aquatic animal's presence by testing for its DNA in the water. This DNA is usually shed through skin cells, feces, or other secretions, and is preserved for a short time in freshwater habitats. Piaggio et al have developed a testing method using PCR to detect Burmese python DNA in water samples, and have shown that this method is reliable up to 96 hours after the DNA has been deposited in the water.

Piaggio et al first established that it was possible to detect reptile DNA in aquatic habitats by placing a captive Burmese python in water, then testing it for python DNA using PCR. They isolated the DNA using a commercial purification kit, then used a primer specific to the python family from a previous study to amplify the sample with PCR. They analyzed the samples with a DNA sequencer and found that the python DNA had been amplified. After they successfully detecting and amplifying the DNA, they designed a primer that would be specific to Burmese pythons. Once they designed a primer, they then tested the specificity of the primer against 2 closely related python species. Only Burmese python DNA was amplified in the PCR, showing that even in samples contaminated with DNA from other snake species, only the Burmese python DNA would be amplified. They then tested the amount of time that could pass before the DNA had degraded too far for the primer to be specific, and found that the sample could be up to 96 hours old and still be accurate.

The final evaluation for the sampling system was a field test of 5 sites known to contain Burmese pythons and one site with no Burmese python. The test had a 100% accuracy rate, showing that it was a reliable test for the presence of Burmese pythons in a given location. Additionally, the method is simple and inexpensive, which makes it an ideal strategy for locating and managing Burmese python populations in Florida.

This study provides an important tool to wildlife management in southern Florida, particularly the Florida Everglades. Because of the damage Burmese pythons can do to the delicate ecosystems in place there, managing them is vital to the survival of many endangered species. Hopefully this new detection system will allow environmental scientists to slow the degradation of these habitats.

Article: Piaggio, A. J., Engeman, R. M., Hopken, M. W., Humphrey, J. S., Keacher, K. L., Bruce, W. E., & Avery, M. L. (2014). Detecting an elusive invasive species: a diagnostic PCR to detect Burmese python in Florida waters and an assessment of persistence of environmental DNA. Molecular ecology resources, 14(2), 374-380.

Link to PDF: http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=2414&context=icwdm_usdanwrc