CEB Committe on Evolutionary Biology

Defensive traits exhibit an evolutionary trade-off and drive diversification in ants

Ants are a highly diverse group of insects that use a wide range of defensive traits to repel both vertebrate and invertebrate attackers. Yet little work has investigated the role of defensive traits on ant diversification or tested possible constraints on the evolution of these traits. In a study recently published in the journal Evolution, CEB graduate student Benjamin Blanchard and co-author Corrie Moreau tested trait-based diversification and the evolutionary trade-off hypothesis. In ants, this hypothesis would predict that defensive traits should be negatively correlated over evolutionary time due to energetic and functional limitations preventing the production of multiple defenses.

Blanchard and Moreau found that a chemical sting – such as that found in fire ants – is negatively correlated with all other traits included in the study. Most of these other traits (large eye size, large colony size, and spines) were also positively correlated with each other, suggesting that they may form a defensive suite of traits.  Furthermore, these three traits were associated with higher rates of species diversification. This work therefore finds support for the evolutionary trade-off hypothesis and highlights the importance of defensive traits in ant evolution. Previous research in ants has tended to focus on behavioral traits and competitive interactions, but the results from this study should promote further investigations into the association between top-down processes (e.g. predator-prey dynamics) and ant traits on both ecological and evolutionary timescales.

Blanchard, B.D., and C.S. Moreau. 2016. Defensive traits exhibit and evolutionary trade-off and drive diversification in ants. Evolution doi:10.1111/evo.13117.

This summary was written by Benjamin Blanchard.