pattern of a switch from fire ant dominance to crazy ant dominance appears to be correct
but the proposed mechanism is not. One possible explanation for the lack of fire ant
replacement by crazy ants is that crazy ant colonies used in crazy ant addition locations
may not have been large enough to send enough workers to baits to deter fire ants.
However, retesting with larger colonies of crazy ants would be difficult due to the
logistical and ethical considerations that must be a part of site selection.
Crazy ants have been shown to be less effective fighters in individual contests
(see Chapter 2), but they did not differ from fire ants in mortality in competing colonies,
and they recruited to baits more quickly and more abundantly than fire ants. Therefore,
fire ants do not have a universal competitive advantage over crazy ants. The ability of
crazy ants to defend food resources from fire ants may be related to both numerical
abundance as well as habitat. Environmental conditions, including soil moisture and
stream flow, have been shown to affect the spread of Argentine ants (Holway 1998,
Menke et al. 2007), so it is not unlikely that environmental condition could affect the
distribution of crazy ants. Even extremely large supercolonies may not be able spread
out of the woods, as open spaces adjacent to heavily invaded woody areas generally have
low to moderate amounts of crazy ants (personal observartion, K. Hom). Abandoned fire
ant mounds, but no active mounds, can sometimes be found in woods heavily invaded by
crazy ants, suggesting that crazy ants may have displaced fire ants in those areas but we
cannot confirm this pattern from our experiments. Regardless, active fire ant mounds are
not found in wooded areas with high crazy ant abundances, suggesting that at the very
least, crazy ants are preventing re-establishment of fire ants in a formerly suitable habitat.
These clues suggest that in addition to an increased competitive ability with increasing
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