Abstract
Biotic interactions are often important in the establishment and spread of invasive species. In particular, competition between introduced and native species can strongly influence the distribution and spread of exotic species and in some cases competition among introduced species can be important. The Caribbean crazy ant, Nylanderia fulva, was recently introduced to the Gulf Coast of Texas, and appears to be spreading inland. It has been hypothesized that competition with the red imported fire ant, Solenopsis invicta, may be an important factor in the spread of crazy ants. We investigated the potential of interspecific competition among these two introduced ants by measuring interspecific aggression between Caribbean crazy ant workers and workers of Solenopsis invicta. Specifically, we examined the effect of body size and diet on individual-level aggressive interactions among crazy ant workers and fire ants. We found that differences in diet did not alter interactions between crazy ant workers from different nests, but carbohydrate level did play an important role in antagonistic interactions with fire ants: crazy ants on low sugar diets were more aggressive and less likely to be killed in aggressive encounters with fire ants. We found that large fire ants engaged in fewer fights with crazy ants than small fire ants, but fire ant size affected neither fire ant nor crazy ant mortality. Overall, crazy ants experienced higher mortality than fire ants after aggressive encounters. Our findings suggest that fire ant workers might outcompete crazy ant workers on an individual level, providing some biotic resistance to crazy ant range expansion. However, this resistance may be overcome by crazy ants that have a restricted sugar intake, which may occur when crazy ants are excluded from resources by fire ants.
Highlights
Biotic interactions between introduced species and native or pre-established exotic species are important influences on the success and spread of invasive species [1,2,3,4,5,6,7]
We explored the potential for competition among two invasive ants by quantifying the aggressive interactions and resulting mortality among workers of the recently introduced Caribbean crazy ant, Nylanderia fulva (Hymenoptera, Formicidae, Formicinae), and the established invasive red imported fire ant Solenopsis invicta (Hymenoptera, Formicidae, Myrmicinae)
Because of the importance of diet in interactions between ants, we examined the effects of both sugar level and prey type on intra- and interspecific aggression in Caribbean crazy ants
Summary
Biotic interactions between introduced species and native or pre-established exotic species are important influences on the success and spread of invasive species [1,2,3,4,5,6,7]. We explored the potential for competition among two invasive ants by quantifying the aggressive interactions and resulting mortality among workers of the recently introduced Caribbean crazy ant, Nylanderia fulva (Hymenoptera, Formicidae, Formicinae), and the established invasive red imported fire ant Solenopsis invicta (Hymenoptera, Formicidae, Myrmicinae). The diet of an ant can influence aggressive interactions between species or colonies of a single species via two mechanisms. Because of the importance of diet in interactions between ants, we examined the effects of both sugar level and prey type on intra- and interspecific aggression in Caribbean crazy ants
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