Hail to the Queens – the polygyne fire ant

Multiple queens from a polygyne fire ant colony (Solenopsis invicta).

Different species of ants employ a variety of social strategies.  As I have mentioned in previous posts, some species of ants form vast colonies of millions of workers, while others maintain smaller social structures of only a few hundred ants (or even less!).  Queens of some species mate singly, while others mate multiply, allowing them to produce half-sibling workers from multiple ‘patrilines’and increase the genetic diversity of the colony.  Although colonies of social insects are most famously known for a s ingle reproductive queen (monogyne colonies), a number of species of ants have multiple queens in each colony (polygyne colonies).

Fire ants are an interesting example to consider.  In their native South American range they are strictly monogyne, and extremely territorial and aggressive towards other fire ants.  However, the fire ants introduced into the United States developed multiple queens sometime during the course of their introduction, and polygyne colonies of fire ants make up the majority of the US population.  Queen numbers can range from a few to hundreds of queens, and fire ants may even accept unrelated queens into the colony.  The acceptance of multiple queens also corresponds to a decrease in aggressiveness and territoriality towards other polygyne fire ant colonies.  This has been suggested as a contributor to the rapid spread of fire ants across the southern US.