Saturday, August 6, 2011
1 Queen, 2 Queen, 3 Queen, 4
This kind of variation within a single species I've learned is more common in ants than previously thought. I've seen this in Monomorium minimum, both queen inbreeding, and loan queen colony founding. The Red Imported Fire Ant, Solenopsis invicta, do this too. With fire ants it's more genetically divided. Monogynic (one queen) colonies produce monogynic colony founding queens while polygynic (more than one queen) reproduce by queen adoption and budding. What's really neat about fire ants is their reaction to water. When floods come, all the members of the colony form a living raft and float away, but while adrift there's nothing stopping two colonies from bumping into one another. Floating for survival is no time for war, so the two colonies may merge into one floating raft, and upon reaching land they remain as one colony regardless of mono or polygynic status before the flood. Perhaps this is how polygynic colonies got their start with this species.
I've seen colonies of Temnothorax sometimes combine to better survive the winter. The following spring they disperse and go their separate ways, though it's unclear if the workers are pared with their genetic mother or just going with the flow. Camponotus pennsylvanicus colonies are strictly monogynic but they still produce sub-colonies as extensions of their nest and territory. Each autumn these satellite locations are abandoned to better overwinter in one location.
Perhaps the most notorious ant to talk about queen number is the Argentine Ant, Linepithema humile. In North America at least, this species spreads exclusively by budding. Queens mate inside the nest causing their numbers to skyrocket at one time of the year. Workers in L. humile have very high standards when it comes to queens though and each year they kill off ~90% of their own queens. This massacre occurs at the same time of year each year. It would seem they don't like their queens to be more than a year old, perhaps to maintain queens at the peak of their egg laying capacity.
Though the queens to polygynic colonies ultimately produce larger colonies, their monogynic counterparts typically live longer.