The Daily Ant

So, you have some communities of ants. You notice that some communities are more diverse than others. In one community, certain species of ants are more common, while in another, different species are more common. How can you explain this coexistence and variation? Dominance hierarchies, perhaps?

Dominance hierarchies have played a key role in ant ecology for many years. These hierarchies describe the relative ability of each species in a community to dominate over others, and tend to be constructed as a single, linear list. In other words, Species A is dominant over Species B which is dominant over Species C which is dominant over blah blah blah. Such a dominance structure is thought to impact species coexistence and variation in community composition across different habitats.

But wait! A recent review and discussion by Dr. Katie Stuble and colleagues challenges this paradigm of dominance hierarchies, suggesting that myrmecologists must improve and move beyond the use of such hierarchies to better explain the processes that structure ant communities. The researchers argue that the most common metrics employed to assess dominance (based on factors ranging from one-on-one aggression to control of food baits) differ in their ecological implications and, critically, are inconsistent in their findings when used on identical sets of data. Furthermore, the concept of a strict dominance hierarchy is unlikely to adequately describe the dynamic and complex nature of real ecological communities. They also offer some suggestions for enhancing future work, including explicitly defining “dominance” and incorporating network theory in studies of dominance, as well as abandoning any uniform application of dominance hierarchies altogether. Check out the paper for more!

Anyone who is a human living in a human society knows that social life carries with it the risk of catching a disease from other nearby humans. Of course, this is also the case for ants in their societies. But a fascinating paper in Ecology and Evolution has recently revealed another commonality: some wood ants, like humans, create antimicrobial drugs. To learn more, check out this nice discussion in Science.

In our recent Philosophy Phriday interview with UNC philosopher Ram Neta, Dr. Neta expressed surprise at the fact that ants have brains. But ants do indeed have brains, as certain fungi know very well, and in a study recently accepted in Developmental Neurobiology, Dr. J. Frances Kamhi and colleagues set out to understand how ant brains may develop differently in a socially simple species versus a more socially complex species.

The researchers hypothesized that a socially simple species, Formica subserica, would exhibit more “neuroplasticity” (flexibility in brain development) than a more socially complex species, Oecophylla smaragdina, which has behaviorally and morphologically distinct worker castes. Dr. Kamhi and colleagues expected that O. smaragdina would have more rigidly determined brain structure due to the maintenance of task specialization in workers that seem less behaviorally flexible than more generalized F. subserica workers. So, they looked at ant brains! In particular, they compared the volume of brain regions that have different functions, and assessed the impact of visual experiences on regions associated with “higher-order sensory integration”.

Do you think the researchers confirmed their hypothesis? If you do, you are wrong! Surprisingly, neither species exhibited differences in brain changes due to visual experiences, and O. smaragdina – not F. subserica – exhibited greater levels of neuroplasticity as workers aged. These results suggest that social complexity, despite associated task specialization, may drive increases in neuroplasticity. It is possible that this increase is necessary to maintain higher levels of coordination and communication seen in complex ant colonies.

In conclusion, ant brains are full of surprises.