Ants Cross the Bridgehead

摘要

Fire ants (Solenopsis invicta) are native to South America, but invasive populations pose increasing problems to ecological and agricultural systems. Fire ant populations have been naturalized in the southern United States for nearly 90 years. More recently, however, populations have become established in California, China, Taiwan, and Australia. Genetic study of over 75 fire ant populations from throughout their native and introduced ranges allowed Ascunce et al. (p. 1066) to identify Argentina as the source of the U.S. population. All newly established populations, however, were derived from the southern U.S. population, mostly by separate invasions. This represents a classic bridgehead effect, where an introduced population serves as the source for subsequent invasions.