Table 1.
The proportion of ants fighting increases with density of nestmates (n = 18/group).
The mean proportions reported are number of fights per ant.
Fig 1.
A) Pavement ant workers responded with fighting after exposure to non-nestmate ants in a density dependent manner (Beta regression; p < 0.0001; n = 18). Isolated ants were unlikely to fight non-nestmate ants and the proportion of trials in which fighting occurred increased with ant density. B) Pavement ant workers increased their interaction rate with nestmates as density increased. (Linear regression; R2 = 0.459, p < 0.0001; n = 7).
Fig 2.
Top panels: Differences in brain 5-HT concentrations between isolated ants (ISO), ants that interacted with live nestmates (NM), and ants that interacted with live non-nestmates (NON-NM) for A) 3 minutes (n = 12 for ISO; n = 11 for NM; n = 9 for Non-NM) and B) 120 minutes (n = 12 for ISO; n = 11 for NM; n = 12 for Non-NM). Bottom panels: differences in brain 5-HT concentrations between isolated ants (ISO), ants that interacted with beads coated in nestmate hydrocarbons (NM BEADS), and ants that interacted with beads coated in non-nestmate hydrocarbons (NON-NM BEADS) for C) 3 minutes (n = 12 for ISO; n = 12 for NM; n = 12 for Non-NM) and D) 120 minutes (n = 12 for ISO; n = 12 for NM; n = 12 for Non-NM). Data reported as mean pg amine/μg protein ± SEM (Dunnett’s test; p < 0.05 *, p < 0.01 **, p < 0.001 ***).
Fig 3.
Pharmacologically increasing brain concentrations of 5-HT and OA (ISO-NON-NM+5-HTP and ISO-NON-NM+OA) increased fighting levels by isolated (ISO-NEST) ants (n = 20), which lacked a recent history of interaction with nestmates, when they met isolated non-nestmate ants (ISO-NON-NM).
Black filled bars indicate ants that fought. Unfilled bar indicate ants that did not fight. SOC-NEST are ants that were allowed to interact with nestmates before interacting with nestmate ants in the assay. SOC-NON-NM were ants that were also allowed to interact with nestmates before interacting with non-nestmate ants. Contingency table with a Chi-square test, p < 0.001, df = 75.80, 5; Bonferroni’s correction (α = 0.009).
Fig 4.
Interactions with ant mimics coated with nestmate cuticular hydrocarbons increased fighting when introduced to a non-nestmate ant (Contingency Table; Chi-square, p < 0.036, df = 6.667, 2; n = 10).
Black filled bars indicate ants that fought. Unfilled bar indicate ants that did not fight.
Fig 5.
Top panels: Differences in brain OA concentrations between isolated ants (ISO), ants that interacted with live nestmates (NM), and ants that interacted with live non-nestmates (NON-NM) for A) 3 minutes (n = 9 for ISO; n = 7 for NM; n = 5 for Non-NM) and B) 120 minutes (n = 10 for ISO; n = 8 for NM; n = 5 for Non-NM). Bottom panels: differences in mean neural OA concentrations between isolated ants (ISO), ants that interacted with beads coated in nestmate hydrocarbons (NM BEADS), and ants that interacted with beads coated in non-nestmate hydrocarbons (NON-NM BEADS) for C) 3 minutes (n = 9 for ISO; n = 12 for NM; n = 11 for Non-NM) and D) 120 minutes (n = 10 for ISO; n = 12 for NM; n = 11 for Non-NM). Data reported as mean pg amine/μg protein ± SEM. (Dunnett’s test; p < 0.05 *, p < 0.01 **, p < 0.001 ***).
Fig 6.
Top panels: Differences in mean neural DA concentrations between isolated ants (ISO), ants that interacted with live nestmates (NM), and ants that interacted with live non-nestmates (NON-NM) for A) 3 minutes (n = 12 for ISO; n = 12 for NM; n = 12 for Non-NM) and B) 120 minutes (n = 11 for ISO; n = 11 for NM; n = 8 for Non-NM). Bottom panels: differences in mean neural DA concentrations between isolated ants (ISO), ants that interacted with beads coated in nestmate hydrocarbons (NM BEADS), and ants that interacted with beads coated in non-nestmate hydrocarbons (NON-NM BEADS) for C) 3 minutes (n = 12 for ISO; n = 10 for NM; n = 12 for Non-NM) and D) 120 minutes (n = 11 for ISO; n = 12 for NM; n = 12 for Non-NM). Data reported as mean pg amine/μg protein ± SEM. (Dunnett’s test; p < 0.05 *, p < 0.01 **, p < 0.001 ***).