The Argentine ants that are trouncing U.S. species may derive much of their competitive power from a loss of genetic diversity during immigration.
Biologists typically lament waning variety in species' gene pools as bad omens for survival. Yet Linepithema humile ants depend on that loss for their conquests, claim Neil D. Tsutsui and his colleagues at the University of California, San Diego.
The invaders look tiny compared with most U.S. ants, but they overwhelm the natives by sheer numbers. Earlier work showed that in their new home, they waste little effort scrapping among themselves. Nests grow fast and can combine forces (SN: 10/31/98, p. 278).
The new study links this amiability to low genetic diversity in the ants' new country. Neighbors accept each other as relatives. In staged ant fights, ants from neighboring colonies in Argentina fought more readily than did their U.S. counterparts.