A new study led by the Texas A&M University has found that a common ant species – Tapinoma sessile, a relatively small type of ant commonly known as the house ant or sugar ant – undergoes physiological and behavioral changes in unnatural settings, such as urban areas.
“Urbanization is a growing habitat around the world, and it’s becoming more important for organisms to develop ways to live when their natural settings are disturbed,” said study senior author Edward Vargo, an expert in Urban and Structural Entomology at Texas A&M. “Studies like this look at important questions regarding this change, ‘Can they adapt to urban environments and how?’”
In their natural environments, house ants create small, single-queen colonies usually found under leaf litter, rocks, and logs. However, in urban and suburban areas, these ants build large, ever-expanding multi-queen colonies around human-made structures such as sidewalks, plant containers, or landscape mulching.
By analyzing the ants’ chemistry (such as levels of hydrocarbons), the genetic make-up of colonies, and ant behavior (like aggression toward familial and outsider ants), the researchers found stark differences based on the environment. Their investigations revealed that, while house ant queens in their natural habitat typically leave the colony they were born in, fly to another suitable location, and attempt to establish a new colony, queens in urban colonies stay in their nest and expand their colony rather than leaving it. As a result, urban queens were closely related and less aggressive toward ants with which they were genetically related. Moreover, behavioral analyses showed that ants in super-colonies were aggressive toward ants with outside genetics.
In addition, polydomous colonies – ant colonies that are spatially separated but socially connected – were found only in urban habitats, suggesting that house ants only create super-colonies in developed areas. Since ants from different urban areas shared some genetic similarities, it seems they are adapting to features which are common in urban environments.
In future research, the scientists aim to compare stable isotopes in the ants to investigate dietary changes and how they relate to natural versus urban environments, while taking into account factors such as temperature and the urban heat island effect.
“The study highlights urbanization’s influence on the evolutionary course for species,” concluded lead author Alexander Blumfeld, who was a doctoral student in Vargo’s lab and is now a postdoctoral fellow at Yale University. “It’s important for us to answer questions related to adaptive evolution, whether it is an invasive species or a forest species adapting to city environments.”
The study is published in the journal Molecular Ecology.
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