Effect of Queen Number on Colony-Level Nutrient Regulation, Food Collection and Performance in Two Polygynous Ant Species.

There is growing appreciation for how social interactions influence animal foraging behavior, especially with respect to key nutrients. Ants, given their eusocial nature and ability to be reared and manipulated in the laboratory, offer unique opportunities to explore how social interactions influence nutrient regulation and related processes. At the colony-level, ants simultaneously regulate their protein and carbohydrate intake; a regulation tied to the presence of larvae. However, even though 45% of the approximately 10,000 ant species are polygynous, we know little about the influence of queen number on colony-level foraging behavior and performance. Here we explored the direct effects of queen number on colony-level protein-carbohydrate regulation, food collection, survival, and brood production in two polygynous ant species (Nylanderia fulva and Solenopsis invicta). For both species we conducted choice and no-choice experiments using small experimental colonoids (20 workers) with 0, 1, or 2 queens. Both species regulated their relative intake of protein and carbohydrate around a P1:C2 mark. However, only N. fulva responded to the addition of queens, increasing overall food collection, biasing intake towards carbohydrates, and over-collecting imbalanced foods. N. fulva also exhibited reduced survival and reproduction on protein-biased foods. In contrast, S. invicta showed no response to queen number and reduced food collection on the protein-biased diet while maintaining high survival and reproduction. Our results demonstrate the potential for queens of some ant species to impact colony-level foraging and performance, with interspecific variation likely being shaped by differences in life history traits.