June 18, 2007
by: jovial_cynic
UPDATE: See the this post for a better identification about this ant.

Fun facts about my species of ant:

Reproductive strategy of the slave ant Formica podzolica relative to raiding efficiency of enslaver species

Formica podzolica serves as host to slave-making ants in North America. We propose that F. podzolica may respond to slavery by two alternative colony-growth and reproductive strategies depending on the raiding ability of the slavemaker:

(1) Rapid colony growth at the expense of producing sexuals to a stage where raiding by unspecialized, facultative slavemakers, capable of exploiting only small colonies, becomes unlikely owing to a strong work force and (2) Early production of sexual offspring at the cost of colony growth to secure some sexual production in an environment with specialized obligate enslavers, capable of raiding large colonies. We tested the strategies by excavating 30 small to moderately large mounds of F. podzolica and measured reproductive parameters of colonies in relation to mound size, worker number, and worker size. Mound area predicted worker number satisfactorily. Worker number correlated significantly with worker head width and with number of worker and sexual offspring. With a growing work force, the proportion of sexual offspring increased in the total offspring. Two thirds of the colonies producing sexuals emitted single sex, sex being independent of colony size. Some of the large colonies produced both sexes with a strong bias toward either sex. The unweighted population-level sex ratio did not differ from even, being 0.52 (numerical) or 0.54 (biomass). Very large mounds (not excavated) had small workers and highly male-biased sex ratios, probably owing to energy constraints set by central-place foraging. Population-level colony ontogeny data did not fit either one of the suggested strategies, but imply a mixture of the two. We discuss an alternative, still untested raid-independent explanation to the ontogeny pattern.

In short - my ants are typically captured by slave-makers. As a way to deal with this, they have two strategies once captured. The two strategies are completely different, and are in response to the type of captors:

In the case of a weak captor, focus on rapid reproduction, and don't produce sexuals. This makes F. podzolica too numerous to control.

In the case of a highly efficient captor capable of capturing large colonies, focus on producing sexuals early on, so sexual activity can still occur once enslaved.

The summary states that in large mounds where F. podzolica has been enslaved, both methods are employed. I believe that's because once the sexuals have come of age, the next step is to apply tactic #2 and breed until they can outnumber the enslavers.


Population genetics of the socially polymorphic ant Formica podzolica

We used microsatellite markers to analyze the hierarchical genetic structure of the North American mound building ant, Formica podzolica. About one-third of all colonies were headed by a single queen (monogynous) whose effective mating frequency was close to one (nestmate worker relatedness r = 0.70), while the remaining colonies were polygynous, with low average nestmate relatedness (r = 0.16). The low worker relatedness found in most polygynous colonies furthermore suggested that the numbers of queens in polygynous colonies of this ant are usually high. Contrary to what has been described from other ants with a queen number dichotomy, we did not find an effect of social form variation on the partitioning of genetic variation above the level of the colony. We found no significant differentiation between the sympatric social forms of F. podzolica, nor did differentiation among populations appear to be affected by colony social organization. These unexpected patterns of genetic structure may have resulted from differences either in the spatial distribution of the social forms or in their social flexibility.

So... my ants are mound building ants. That might explain why they're bringing dirt from the main chamber into the nursery. I might consider building a tall chamber that allows them to move dirt around more easily. My current foraging chamber has the Plexiglas pressed flat against the dirt, so they can't build mounds with it.
np category: ants


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