The evolution and functional implications of socially synchronized rhythms in ants.

Collective behaviors are widespread in social animals, yet the factors driving the evolution of diverse collective phenotypes across species are not well understood. Due to their taxonomic diversity and small colony sizes, acorn ants (genera Temnothorax and Leptothorax) provide us with a valuable model clade for studying the evolution of emergent collective behaviors. In this talk, I summarize my work on the socially synchronized rest/activity rhythms of acorn ants. In the first part of my presentation, I show how synchronized activity can improve spatial accessibility inside of ant nests by suppressing the formation of traffic jams in walking ants. I then present a comparative study involving 22 species and over 1,500 behavioral rhythm time series from hundreds of colonies and isolated individuals, totaling over 1.5 years of behavioral data. This study revealed that the rate of phenotypic evolution for colony-level phenotypes can exceed the rate of evolution of analogous traits measured at the level of individual ants. Finally, by assembling colonies with experimentally manipulated demographics, I show that asymmetry in the social interactions between queens and worker ants may play a crucial role in the evolution of the colony-level differences between species. Based on my results, I hypothesize that more rapid evolution of emergent phenotypes relative to lower-level phenotypes is a general feature of complex biological systems.