The evolution of stridulatory communication in ants, revisited

Abstract

The presence and use of a stridulatory organ (SO) to produce vibrational signals is highly variable and structured within the ants. The file and scraper that make up the SO are specialized morphological features not used for functions other than stridulation (a vibratory signal production mechanism) and not found in non-stridulating species. It has been hypothesized and generally accepted that the stridulatory organ first evolved to alert nest mates of burial and need for rescue. Based on this premise, arboreal species are expected to exhibit a reduction of use of vibrational signals when compared to terrestrial species. Using ancestral state reconstruction, we have mapped the presence of the SO on a molecular phylogeny of the ants and found support for the hypothesis that the SO evolved multiple times in the ants. We quantitatively tested the hypothesis that stridulation evolved initially to signal burial/rescue by comparing the presence of the SO to general foraging and nesting preferences for 76 genera evenly spread throughout the currently accepted ant phylogeny. We found that a greater proportion of genera that are considered primarily arboreal possess a SO, as opposed to the ground nesting genera, and none of the five entirely subterranean genera included in this study possess a SO. We therefore reject the previous hypothesis regarding burial/rescue signaling.