How Adaptive is Division of Labor?

Much of the theory behind division of labor - be it in ants or in factory workers - is based on the premise that since workers specialize in different jobs, the the optimum proportion of different kinds of workers should change when conditions change. For example, many ants have both "worker" and "soldier" castes. When a colony finds themselves in a environment with more competition, theory predicts that the colony should shift its workforce of ants to relatively more "soldiers."

As intuitive as it is, surprisingly few demonstrations of this fundamental prediction actually have been found in nature.

The purpose of this study was to look for novel evidence for shifts in caste proportions with differences in the environment. However, rather than looking at a single colony over a short period of time and see how it might change, I took the approach of comparing different geographic populations to look for evidence that their colony caste proportions had diverged -perhaps evolutionarily - to new optima suited to their different environmental circumstances. Within this study are some interesting findings as to how development might constrain natural selection in unexpected ways.

Hundreds of thousands of ants counted, and hundreds of deep holes dug in the Florida heat, these are the results:

Click the image of the Wrestilng Ants above for the PDF.