We assess nestmate queen relatedness and the genetic similarity of neighboring nests in the polygyne (multiple-queen) social form of the introduced fire ant Solenopsis invicta using both nuclear and mitochondrial markers. We find that estimates of queen relatedness calculated with both types of markers do not differ statistically from zero. Furthermore, there is no significant relationship between the genetic similarity and geographic proximity of nests in each of six study sites. In contrast to these findings, sites show strong mitochondrial, but no nuclear, genetic differentiation. Our results suggest that nonnestmate queen recruitment occurs at a high frequency in introduced populations of this species. Moreover, queens within nests seem to represent a random sample of the queens within the site in which they reside. Therefore, kin selection models that rely on the recruitment of only nestmate queens to explain the persistence of polygyny in ants do not apply to polygyne S. invicta in its introduced range.
Keywords: Evolution; Solenopsis invicta; fire ants; introduced species; monogyny; mtDNA; polygyny; relatedness; social insects.
© 1998 The Society for the Study of Evolution.