Submitted to: Diversity and Distributions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/2009
Publication Date: 7/1/2009
Citation: Yang, C., Shoemaker, D.D., Wu, J., Lin, Y., Lin, C., Wu, W., Shih, C. 2009. Successful establishment of the invasive fire ant Solenopsis invicta in Taiwan: Insights into interactions of alternative social forms. Diversity and Distributions. 15(4):709-719. Interpretive Summary: Fire ants are considered significant ecological, agricultural, and public health pest throughout their invasive range in the U.S.A. A scientist at the Center for Medical, Agricultural, and Veterinary Entomology, USDA-ARS, Gainesville, Florida and scientists from the National Taiwan University describe here the results of a study aimed at determining the distribution of two social forms of fire ants in two separate infested areas in Taiwan. We found that the distribution of the two social forms differs dramatically between the two infested areas, consistent with different invasion histories regarding the original make-up of individuals comprising the initial founder group. Our results also suggest that the distinct reproductive biology of the two social forms has shaped the successful establishment and subsequent spread of fire ants in Taiwan and that subsequent competition between the two forms may affect the long-term persistence and potential for spread of this pest ant species. This collaborative study represents an important contribution to the ongoing efforts aimed at eradicating this invasive pest in Taiwan and elsewhere.
Technical Abstract: Understanding the factors underlying the successful establishment of invasive ant species is critical for developing quarantine strategies to prevent additional invasions as well as for determining how such species overcome the selective pressures occurring in invaded areas. Although several studies have revealed differences in the social organization and population genetics of invasive ants in their native and introduced ranges, few ant studies have considered the potential interactions between alternate social forms within newly-invaded areas simply because most invasive ants are characterized as polygyne (multiple queens) or unicolonial. Recent studies indicate that two distinct social forms (polygyne and monogyne) of the red imported fire ant Solenopsis invicta occur in two separately invaded areas in Taiwan (Taoyuan and Chiayi). We employed intensive sampling methods and diagnostic PCR assays to determine the distribution of these two social forms in both infested areas in Taiwan. Our results indicate that the distribution of social forms differs dramatically between the two infested areas, consistent with different invasion histories regarding the original make-up of individuals comprising the initial founder group. The Taoyuan population likely was colonized initially by ants of both social forms, with the subsequent spread characterized by continuous outward movement of the two forms from the initially invaded area, particularly the monogyne form. In contrast, the initial founders of the Chiayi population likely were of the polygyne social form only, suggesting the monogyne social form in this population appeared only recently and likely arose directly from polygyne queens converting to the alternate social form. Our results suggest that the distinct reproductive biology of the two social forms has shaped the successful establishment and subsequent spread of S. invicta in these infested areas and that subsequent competition between the two forms may affect the long-term persistence and potential for spread of this pest ant species.