Data from: Nutritional challenges of feeding a mutualist: testing for a nutrient-toxin tradeoff in fungus-farming leafcutter ants

The biochemical heterogeneity of food items often yields tradeoffs as each
bite of food tends to contain some nutrients in surplus and others in
deficit, as well as other less palatable or even toxic compounds. These
multidimensional nutritional challenges are likely compounded when foraged
foods are used to provision others (e.g. offspring or symbionts) with
different physiological needs and tolerances. We explored these challenges
in free-ranging colonies of leafcutter ants that navigate a diverse
tropical forest to collect plant fragments they use to provision a
co-evolved fungal cultivar. We tested the prediction that leafcutter
farmers face provisioning tradeoffs between the nutritional quality and
concentration of toxic tannins in foraged plant fragments. Chemical
analyses of plant fragments sampled from the mandibles of Panamanian Atta
colombica leafcutter ants provided little support for a nutrient-tannin
foraging tradeoff. First, colonies foraged for plant fragments ranging
widely in tannin concentration. Second, high tannin levels did not appear
to restrict colonies from selecting plant fragments with blends of protein
and carbohydrates that maximized cultivar performance when measured with
in vitro experiments. We also tested whether tannins expand the realized
nutritional niche selected by leafcutter ants into high-protein dimensions
since: 1) tannins can bind proteins and reduce their accessibility during
digestion, and 2) in vitro experiments have shown that excess protein
provisioning reduces cultivar performance. Contrary to this hypothesis,
the most protein-rich plant fragments did not have highest tannin levels.
More generally, the approach developed here can be used to test how
multidimensional interactions between nutrients and toxins shape the costs
and benefits of providing care to offspring or symbionts.