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Distinct colony boundaries and larval discrimination in polygyne red imported fire ants (Solenopsis invicta)
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  • MacKenzie Kjeldgaard,
  • Pierre-André Eyer,
  • Collin McMichael,
  • Alison Bockoven,
  • Joanie King,
  • Ayumi Hyodo,
  • Thomas Boutton,
  • Edward Vargo,
  • Micky Eubanks
MacKenzie Kjeldgaard
Texas A&M University College Station

Corresponding Author:mkjeldgaard@tamu.edu

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Pierre-André Eyer
Texas A&M University College Station
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Collin McMichael
Texas A&M University College Station
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Alison Bockoven
Texas A&M University College Station
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Joanie King
Texas A&M University College Station
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Ayumi Hyodo
Texas A&M University College Station
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Thomas Boutton
Texas A&M University College Station
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Edward Vargo
Texas A&M University College Station
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Micky Eubanks
Texas A&M University College Station
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Abstract

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.
13 Aug 2021Submitted to Molecular Ecology
13 Aug 2021Reviewer(s) Assigned
21 Sep 2021Review(s) Completed, Editorial Evaluation Pending
30 Sep 2021Editorial Decision: Revise Minor
28 Oct 20211st Revision Received
28 Oct 2021Review(s) Completed, Editorial Evaluation Pending
02 Nov 2021Editorial Decision: Accept
Feb 2022Published in Molecular Ecology volume 31 issue 3 on pages 1007-1020. 10.1111/mec.16264