(1st Place) Predation as a driver of morphological diversification in ant mandibles

Lineages diversify into different ecological niches with phenotypes that are different in form and function. Ants evolved a broad trophic spectrum and perform vastly different behaviors, universally exhibit a social lifestyle, and their range of body plans is highly disparate. Mandibles are the primary tools that ants use in social, environmental, and dietary interactions, but we still lack an understanding of the factors that promote their diversification. Here, I use a comparative approach to show how diet relates to shape diversity and investigate whether more diverse lineages have a broader range of mandible shapes. I quantify shape with geometric morphometric methods from 3D models of more than 200 ant genera without neglecting worker polymorphisms or morphologically variable ant groups. I show that three archetypical mandible shapes broadly summarize morphological diversity. Variations on a standard and ancestral “triangular mandible” are prevalent in all larger clades involved in any kind of lifestyle. Elongated forms are often associated with specialized predatory functions (‘weaponization’) and occur in most lineages but by modifying different subregions of the mandible thus increasing the overall diversity of mandible shapes. Even in species-poor clades, extreme shapes occur. More restrictedly, ants advance into a region of morphological space where the mandible is shortened to possibly increase bite strength. Ultimately, I want to ask how diverse functions and shapes in different body parts map towards each other to result in complex morphological diversity patterns.