The number of theoretical phenotypes that organisms can acquire through evolution is nearly limitless. Despite the vast phenotypic space, some complex traits evolved repeatedly and independently in the process of convergent evolution. The study of convergent biological systems can help us address an open question in biology - how phenotypic space is explored in evolution and why some phenotypes evolve multiple times.
Here, we studied the convergent phenotypes in termites. Termite soldiers are equipped with morphological adaptations for a colony defense. Soldiers in more than one hundred species evolved an extraordinary defensive modification of mandibles - so called snapping. Snapping mandibles are biological springs which are gradually loaded by pressing them against each other until they slip and release the accumulated energy in a single strike.
Using combination of X-ray microtomography, high-speed video recording, and phylogenetic and ancestral state reconstruction we found that termites evolved snapping 4-7 times independently. We identified possible morphological trajectories and ecological drivers that led to repeated evolution of snapping and to transitions between specific types of snapping. We found that termites convergently reached peak mandibular speeds exceeding 100 m/s - likely approaching the limits of biological spring design - using several functionally distinct snapping mechanisms.