A Tale of Turtle Ants and Soldier Evolution

Using a mathematical model informed by extensive knowledge of turtle ant biology, Dr. Planqué and colleagues considered how disruptive selection might have given rise to two different worker castes in the turtle ants. The results of their simulations using their model suggest that a soldier caste may in fact arise from disruptive selection driven by competitive interactions. In particular, in their model, the inclusion of coupled ecological specialization and defensive trait parameters produced simulation outcomes that include the evolution of a soldier caste. In other words, when the presence of a new caste with defensive traits promotes the use of a narrower range of resources, a soldier caste evolves. This is surprising, because the prevailing view is that worker castes arose as way to access a wider range of resources.