Submitted to: Biological Invasions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/8/2010
Publication Date: 2/24/2010
Citation: Yang, C., Yu, Y., Valles, S.M., Oi, D.H., Chen, Y., Shoemaker, D.D., Wu, W., Shih, C. 2010. Loss of microbial (pathogen) infections associated with recent invasions of the red imported fire ant Solenopsis invicta. Biological Invasions. 12(9):3307-3318. Interpretive Summary: Fire ants are considered significant ecological, agricultural, and public health pest throughout their invasive range in the U.S.A. Scientists at the Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, Gainesville, Florida and scientists from the National Taiwan University University describe here the results of a survey for pathogens infecting fire ants in their native and introduced ranges. These surveys showed that the total number of enemy species is lower in the recently invaded areas compared with both South American and US fire ant populations and support the general prediction that invasive species lose many of their natural enemies during invasion. While the successful invasion of S. invicta in these recently invaded areas may be explained partly by the absence of natural enemies, other factors likely have been important as well.
Technical Abstract: Loss of natural enemies during colonization is a prominent hypothesis explaining enhanced performance of invasive species in introduced areas. Numerous studies have tested this enemy release hypothesis in a wide range of taxa but few studies have focused on invasive ants. We conducted extensive surveys for the presence of six microbes in recently established populations (California, Australia, New Zealand, Taiwan, and China) of the invasive fire ant Solenopsis invicta. These microbes include Wolbachia, two microsporidia (Kneallhazia solenopsae and Vairimorpha invictae) and three RNA viruses (SINV-1, -2 and -3), all of which previously have been reported in native South American populations of S. invicta. These surveys showed that the total number of enemy species is lower in the recently invaded areas compared with both South American and US populations. Only two microbes were found in any of these recently invaded areas: SINV-1 was detected in all surveyed populations except Australia and New Zealand, and SINV-2 was detected in California and Taiwan only. These results support the general prediction that invasive species lose many of their natural enemies during invasion. Further, the conspicuous absence of some of these microbes in these areas may result from strong selection against founders due to fitness costs associated with harboring detrimental infections rather than the alternative hypothesis that they simply were absent among the original founders. While the successful invasion of S. invicta in these recently invaded areas may be explained partly by the absence of natural enemies, other factors likely have been important as well.