DSSS - Evolutionary success of the turtle ants through extreme trait evolution and symbiosis

Key innovations are traits that allow a group of organisms to diversify through occupying new ecological niches. Symbiosis is an often-overlooked trait that can serve as a key innovation and use the turtle ants to explore this idea. The turtle ants (genus Cephalotes) are a diverse group of animals distributed from the southern United States throughout Central and South America allowing us to test hypotheses about their phylogeny and biogeographic origin and history. Soldiers of the genus have extreme morphologies to allow them to occupy and defend their entirely arboreal habitats and we use comparative genomics and developmental transcriptomics to explore how these soldiers evolved. In addition turtle ants have very low stable isotopic signatures and rely on gut bacteria to enrich their diets which we demonstrate occurs through nitrogen recycling. Experimental manipulations and analytical chemistry show that they can use the nitrogen provided by their symbiotic bacteria to invest in their cuticle to strengthen their external armor. These multiple traits have allowed the turtle ants to thrive in the nutrient limited canopy of the American tropics.