corresponding increase in mortality. Therefore, a crazy ant colony that has been
competitively excluded from sugar sources by fire ants or other ants may engage intense
fights, inflicting various degrees of mortality on other ant species without suffering high
mortality themselves. Combined with the fact that differences in diet showed no sign of
affecting nestmate recognition, large supercolonies of sugar-limited crazy ants may
challenge fire ant dominance in certain areas by overwhelming fire ant nests with
considerable numbers of very active workers that readily engage in fights. Nevertheless,
because fire ants have almost half as much mortality as crazy ants in individual
interactions, fire ant colonies could provide biotic resistance to the crazy ant invasion in
places where fire ants outnumber crazy ants and can afford to engage in fights without
serious losses in workers or foraging efficiency. In sum, these findings help explain the
occurrence of large supercolonies of crazy ants but suggest that established fire ants may
provide some biotic resistance to crazy ants, especially if crazy ants are not sugar-limited.
Further studies on colony-level interactions will further elucidate the ability of an
established invasive species to resist the spread of a newly introduced species.
Acknowledgements
I would like to thank Matt Barajas, Juli Carrillo, Marilu Corona, Christopher
Gabler, Simrnier Jones, Max Quintanilla, Evan Siemann, and Erica Soltero for their field
and laboratory assistance. Financial support was provided by a Wray-Todd Fellowship to
KH.
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