Data from: Distinct colony boundaries and larval discrimination in polygyne red imported fire ants (Solenopsis invicta)

Evaluating the factors that promote invasive ant abundance is critical to
assess their ecological impact and inform their management. Many invasive
ant species show reduced nestmate recognition and an absence of boundaries
between unrelated nests, which allow populations to achieve greater
densities due to reduced intraspecific competition. We examined nestmate
discrimination and colony boundaries in introduced populations of the red
imported fire ant (Solenopsis invicta; hereafter, fire ant). Fire ants
occur in two social forms: monogyne (colonies with a single egg-laying
queen) and polygyne (colonies with multiple egg-laying queens). In
contrast with monogyne nests, polygyne nests are thought to be
interconnected due to the reduced antagonism between non-nestmate polygyne
workers, perhaps because polygyne workers habituate the colony to an odor
unique to Gp-9b-carrying adults. However, colony boundaries and nestmate
discrimination are poorly documented, particularly for worker-brood
interactions. To delimit boundaries between field colonies, we correlated
the exchange of a 15N-glycine tracer dissolved in a sucrose solution with
social form. We also evaluated nestmate discrimination between polygyne
workers and larvae in the laboratory. Counter to our expectations,
polygyne colonies behaved identically to monogyne colonies, suggesting
both social forms maintain strict colony boundaries. Polygyne workers also
preferentially fed larval nestmates and may have selectively cannibalized
non-nestmates. The levels of relatedness among workers in polygyne
colonies was higher than those previously reported in North America (mean
±SE: 0.269 ± 0.037). Our study highlights the importance of combining
genetic analyses with direct quantification of resource exchange to better
understand the factors influencing ant invasions.