Chapter 2
The Effect of Diet on Intra- and Interspecific Interactions of the
Rasberry Crazy Ant (Paratrechina sp. wt.pubens)
Abstract
Biotic interactions are often important in the establishment and spread of invasive
species. In particular, competition with species in the introduced range of an exotic
species can be significant in preventing an exotic species from colonizing areas of
suitable habitat (Walters and Mackay 2005, Menke et al. 2007). Here we examined
interference competition in the Rasberry crazy ant, Paratrechina sp. nr. pubens, which
was recently introduced to the Gulf Coast of Texas, by studying intraspecific interactions
between nests OfRasberry crazy ants and interspecific interactions with the red imported
fire ant, Solenopsis invicta. Specifically, we examined individual-level interactions in
three sets of ants: 1) between crazy ant workers and either small (minor) or large (major)
fire ant workers, 2) between crazy ant workers from different nests receiving one of two
protein sources and either high or low doses of sugar, and 3) between fire ants and crazy
ant workers receiving the different diets. We found that large fire ants fought less often
with crazy ants than did 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
antagonistic encounters. Differences in diet did not alter interactions between crazy ant
workers from different nests, but sugar level did play an important role in antagonistic
interactions with fire ants, as crazy ants on a low sugar diet earned higher aggression
scores. Our findings suggest that fire ants may outcompete crazy ants on an individual
level, providing some biotic resistance to crazy ant range expansion. However, fire ants