Territorial aggression in a unicolonial and invasive social insect.
Holway, David*,1, Thomas, Melissa 1, Payne, Chris2, Suarez, Andrew2, Tsutsui, Neil3, 1 Division of Biological Sciences, La Jolla, CA, US2 Department of Entomology, Urbana, IL, US3 Department of Ecology and Evolutionary Biology, Irvine, CA, US
ABSTRACT- Invasive ants are noteworthy because of their common (although not universal) tendency to form large supercolonies in their introduced ranges, a phenomenon known as unicoloniality. This syndrome may help explain the ecological success of invasive ants because supercolonies avoid paying costs associated with intraspecific territoriality. Although lab studies illustrate how intraspecific aggression can restrict colony growth through increased mortality and reductions in per capita efficiencies in competitive performance, next to nothing is known about how established colonies interact when they contact one another under natural circumstances. Here, we report the first data on the behavioral and genetic characteristics of naturally occurring territory boundaries in introduced populations of the Argentine ant, a widespread abundant and ecologically damaging invasive ant species. We address four specific questions. (1) Are territory boundaries spatially discrete? (2) If so, do boundaries shift position over time? (3) Do abutting colonies interact aggressively with one another under natural circumstances? If so, how often do colonies fight with one another, and what potential costs are incurred? (4) Are behavioral discontinuities correlated with genetic differences between supercolonies? Answers to these questions will shed light on the generality of previous experimental studies and are needed to discriminate among the different competing hypotheses that have been proposed to explain the existence of colony structure variation in this and other social insect species.
Key words: invasion, ant, behavaior, territoriality
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