Mystery of the Global Invasion of Red Imported Fire Ants Cracked---NTU Department of Entomology Research Paper Published in Science

The internationally renowned journal Science published a paper on February 25th, 2011 on the findings of the mystery of the global invasion of red imported fire ants (Solenopsis invicta). The paper was the result of a transnational collaborative research among NTU Department of Entomology faculty members Dr. Chin-Cheng Yang, Professor Cheng-Jen Shih, and Professor Wen-Jer Wu, the U.S. Department of Agriculture, the University of Florida, the Australian Biosecurity Department, the University of Georgia and the University of Lausanne of Switzerland.

It analyzed the route of invasion of Solenopsis Invicta (imported red fire ants), and established a milestone for the prevention of its invasion. Listed as one of the top 100 invasive species, the red imported fire ants once caused ecological upheaval all over the world and grated on the nerves of the citizens of Taiwan. Because the ways and means of the proliferation of the red imported fire ant remain unknown to men, the world at large was defenseless against its invasion. Now that the collaborative research team among NTU Department of Entomology, the United States and Australia has successfully cracked the mystery of its invasion, the global history against the invasion of the red imported fire ants will be rewritten.

The red fire ants first invaded the United States in the early 1930s, then they quickly spread to the 17 states in the Southeast. At the end of the 20th century, none of the regions in California and Mexico were spared, resulting in a total infected area of two hundred million hectares and nearly eight billion dollars of losses. At the beginning of the 21st century, the red fire ants crossed the Pacific and found their ways to Australia and New Zealand. Later, just within a few years, Taiwan, Hong Kong, Macau and China also fell prey to their power. The red fire ants caused great harm to humans and their environments. In the infected areas, their presence severely impacted the ecology, agricultural economy, and the lives of people. Therefore, every country in the world tried to do its utmost to eliminate the fire ants.

In Taiwan, although considerable experiences have been accumulated in regard to the containment of red imported fire ants, so far there has been no effective cure. At the end of 2003, reports of red fire ants pillaging Taiwan began to run rampant in the press, so, in response to the epidemic, Taiwan’s Department of Agriculture worked closely with National Taiwan University to establish the “National Red Imported Fire Ants Control Center”, and waged a three-phase (prevention, containment, and eradication ) campaign to control the termites. The basic research work related to this campaign was conducted by a team led by Professors Cheng-Jen Shih and Wen-Jer Wu.

In order to locate the source of Taiwan’s fire ants, Dr. Chin-Cheng Yang participated in Dr. Shoemaker’s global invasion program of the fire ants (US Department of Agriculture) from 2006. In 2008, he received grants from the Maxima Program of the National Science Council, went to the Imported Fire Ants and Household Insects Research Center of the U.S. Department of Agriculture to conduct related research and to write his thesis. In the meantime, the fire ants research team of NTU also participated in a transnational research program on the de-sequencing of fire ants genomes, and the results were published in the PNAS(Proceedings of the National Academy of Sciences, PNAS) in February, 2011.

The research team used a large number of genetic markers, including 66 microsatellites, 2mitochondrial gene sequences and nuclear genes with high variations. Coupled with all kinds of genetic analyses and simulation, the researchers found that all recent invasions were independent invasions, and the sources of the invasions can be traced back to the flocks from the United States. This shows that fire ants, after having migrated from South America to the United States, have undergone significant changes in their life history characteristics and in their population characteristics. These changes made the fire ants become highly invasive species which could establish a bridgehead population locally, with a capacity for invasion at any time. The frequent international trade and the constant traffic exchanges of the United States provided excellent channels of invasion for the fire ants, by which the bridgehead populations could be transported to other areas. Under the interactions of these two conditions, fire ants became a global problem. If the nations of the world do not take a proactive stand on termite control, they are liable to become the next bridgehead for the fire ants.

NTU’s research achievements not only successfully established the spreading model of the fire ants, but, more importantly, in the level of practical applications, they built a complete global genetic database, allowing newly invaded nations to quickly identify the source of the fire ants, and adopt emergency quarantine measures accordingly.