Living Large
Native ants build giant colonies in cities
A native ant species that occupies small colonies in undisturbed forests can form enormous supercolonies with hundreds of queens in urban areas, a scientist has found.
The species, the odorous house ant (Tapinoma sessile), is found in much of North America. As described in Biological Invasions, researcher Grzegorz Buczkowski of Purdue University sampled colonies from three different types of environments in Indiana: natural forest, “semi-natural” areas with some human disturbance, and the cities West Lafayette and Lafayette.
The differences were dramatic. Colonies in natural areas had only one nest, one queen, and an average of 74 ants. Meanwhile, the urban colonies contained an average of 7 nests, 238 queens, and more than 58,000 ants per nest, Buczkowski found. The semi-natural colonies were somewhere in between, maintaining hundreds of ants but only single queens and nests.
The findings suggest that even native species can take on invasive characteristics in urban environments, the study says. While T. sessile shares its habitat with other ant species in natural areas, it appears to have outcompeted many species in cities. Researchers should consider the effects of fast-spreading native species, says Buczkowski, not just exotic invaders. – Roberta Kwok
Source: Buczkowski, G. 2010. Extreme life history plasticity and the evolution of invasive characteristics in a native ant. Biological Invasions DOI: 10.1007/s10530-010-9727-6.
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