Different Dome, Better Home

Polydomy. It’s a thing. It’s a thing where a single ant colony occupies completely separate nesting chambers rather than a single nest site. Polydomy, in creating a more distributed nest structure, has been theorized to increase foraging efficiency and enhance acquisition of a more diverse set of resources. Yet, despite the prevalence of hypotheses and theoretical work relating to polydomy, little work to date has experimentally tested the impact of polydomy on foraging efficiency.

Temnothorax ants in their acorn home. Photo: Alex Wild

Cue Dr. Nathalie Stroeymeyt and colleagues, in a study recently published in Proceedings of the Royal Society B. Using a species that exhibits some degree of polydomy, Temnothorax nylanderi, these researches set up a lab design where they could compare various foraging outcomes between polydomous colonies and monodomous colonies. For example, in the first experiment, some colonies were set up in two adjacent, divided chambers, and the others were placed in single chambers, with the total nesting area held constant. Stroeymeyt and colleagues conducted three experiments in total to assess evidence for different hypothesized effects of polydomy:

  1. Impact of polydomy on task allocation and foraging output: Does the type of nest impact the number of workers foraging and the type of food they forage for (honey water or flies)?
  2. Impact of polydomy on food search time: Does polydomy increase the average rate in which workers obtain resources?
  3. Impact of polydomy on diet diversification: Is polydomy an adaptation to diversify resources?

What did the researches find, using their elegant experimental designs? In experiment (1), they found that polydomy does increase foraging output, specifically for obtaining the protein food source. In experiment (2), Stroeymeyt and colleagues discovered that in polydomous nests, the average worker obtained resources quicker, likely due to inter-nest communication. In experiment (3), they showed that polydomous nests were constructed more often when protein was a more limited resource.

So, when it comes to choosing a new home, Steoymeyt and colleagues have provided robust experimental evidence showing that at least in T. nylanderi, polydomy improves foraging efficiency in a number of ways. Additional, similar studies in different species would potentially provide further evidence that these advantages are consistent across species, contributing to our understanding of general rules driving the evolution of polydomy.