Scientists contributing to exotic species invasion of Antarctica

South African scientists have published a new study illustrating how exotic species are accidentally introduced to Antarctica. The researchers found that scientific operations and other visitors are likely vectors for invasive plants by unknowingly carrying seeds on clothes and in luggage and cargo. Based on the findings, the study authors offered recommendations on steps that can be taken to minimize the introduction of invasive species by visitors to the continent.

Fieldwork on Melnik Peak, Livingston Island. This study is particularly important for a couple of reasons:

1) A number of invasive species such as the alien Poa annua have already established in Antarctica threatening the biodiversity of the continent - particularly in the sub-Antarctic where the climate includes relatively mild temperatures and high rainfall. With global warming, the area of the continent prone to invasion will likely increase.

2) Most research in the field of invasion biology looks at the dynamics of how newly introduced species dominate an area and what measures managers can take to control invasive species after they establish. Relatively few studies have looked at how invasive species become introduced to new areas in the first place.  Antarctica offers an ideal setting to look at that process because with visitors entering through a few well-defined points, the pathways for introduction are easier to track.

Study methods and results

•The researchers looked at newly arriving cargo and luggage to the South African National Antarctic Programme and identified all the exotic seeds encountered. They found a total of 1400 seeds representing 99 taxa. Of these, at least 64% of the genera are known to be exotic in the Antarctic region. In the luggage, they found on average 5 seeds per visitor.
•The study also conducted an elaborate method of stashing painted, sterilized seeds in cargo, luggage, and visitors' clothing to estimate what percentage of the seeds carried into Antarctica are actually left behind. They calculated a drop-off of 53% for clothing and 20% for cargo.
•The researchers ran seeds through washing machines to see what effect the treatment had on germination. They found that washing reduced germination but the temperature needed to completely sterilize seeds was too high to be used without damaging the high performance clothing typically used in Antarctica.
•The study also found propagules of native species, which suggests that expeditions may be transporting native plants from one part of the continent to the other. This could have a variety of negative ecological and evolutionary impacts.

The researchers offered the following recommendations:

•The findings indicate that transport hubs act as stepping-stones for invasion. Intensive control efforts should focus on keeping these loading and drop-off areas weed free.
•Cargo containers should be designed to reduce the catching of seeds and should be cleaned and inspected carefully prior to loading and transfer to a cargo hold.
•Socks were found to be particularly problematic in terms of capturing seeds. Simple measures such as providing new socks for each expedition and cleaning bags thoroughly could substantially reduce the propagule load.
•Washing of clothes can reduce germination but the temperature needed to sterilize to seeds will likely damage high performance clothing. Irradiation of clothing may be an alternative.
•Another alternative is to ship new clothing to a research station and leave it after it has been used.

--Reviewed by Rob Goldstein

Lee, J., & Chown, S. (2009). Breaching the dispersal barrier to invasion: quantification and management Ecological Applications, 19 (7), 1944-1959 DOI: 10.1890/08-2157.1