Agee entomologists have shown how ant colonies adapt to urbanization

Close-up of an ant standing on the edge of a leaf

Research has focused on changes in ant physiology and behavior based on their environment and hopes to shed light on ant species and other animals that are evolving amid urbanization.


Texas A&M AgriLife photo by Michael Miller

search by Texas A&M AgriLife Research Scientists in Texas A&M Entomology Division He showed that a common type of ant undergoes physiological and behavioral changes under abnormal conditions.

Consistent signatures of urban adaptation in the indigenous invasive Tapinoma ant in urban areasPosted in Molecular ecology The work of lead author has included Alexander Blumenfeld, former graduate research assistant; Ed Fargo, Senior Detective and talented head of Architectural and structural entomology; Angel Helms, chemical ecologist and assistant professor; and Pierre-Andre Ayer, a postdoctoral researcher, all in the Department of Entomology.

“Urbanization is a growing habitat across the world, and it has become crucial for organisms to develop ways to live when their natural conditions are disturbed,” Fargo said. “Studies like this look at the important questions related to this change,” Can they adapt to urban environments and how? “

The environment affects ant behavior and chemical changes

The study focused on Tapinoma sessile, a relatively small type of ant known as the house ant or sugar ant. They are the most common home infested ants across the United States

In its native environment, the house ant creates small, one-queen colonies usually found under foliage, rocks, and tree trunks, Fargo said. But in suburban/urban areas, house ants build ever-expanding multi-queen colonies around man-made structures such as sidewalks, plant containers, and landscape mulch.

Fargo said the study provides a wide range of scientific applications related to biological and behavioral change caused by environmental conditions across the animal kingdom. It can also provide insights into how invasive species interact with new environments on them.

“The change is very similar to invasive ants once they go from their original range to an invasive range,” he said. “The idea is to better understand this syndrome in ant species that can take in a small, inconspicuous colony which then becomes an economic and ecological problem as the destroyed colonies get bigger and bigger.”

Answer questions about adaptive evolution

Close-up of two ants on a sheet of paper, one walking across the top and one hanging from the side

Researchers continue to study how and why changes in the environment such as urbanization lead to behavioral and physiological adaptations in ants.


Texas A&M AgriLife photo by Michael Miller

Fargo said the researchers used a large genetic database to identify chemical and behavioral changes that affected the ants’ social organization. They explored and compared population genes and breeding structure within and between ants in several urban and non-disturbed natural sites within their range.

Odorless house ants have been observed and analyzed in natural and disturbed locations across the country including Indiana, Arkansas, Colorado and California.

Fargo said the team analyzed the ants’ chemistry, such as hydrocarbons and the genetic makeup of colonies and behaviors, such as aggressiveness toward family ants and intruders, and found stark differences based on the environment.

The study found that house ants in urban and natural areas exhibited adaptations that led to genetic focus. Fargo said that home ant queens in their natural habitat usually leave the colony in which they were born, fly to another suitable location and try to establish a new colony. In urban colonies, queens stay in the nest and expand the colony rather than leave.

As a result, urban queens were more closely related and less aggressive towards genetically related ants. Behavioral analyzes showed that ants in giant colonies were aggressive towards ants with exogenous genes.

Additionally, polyphyletic colonies, which are ant colonies that are spatially separate but socially related, were only present in urban habitats, Fargo said. This indicates that domestic ants only create super colonies in developed areas. Ants from different urban areas share some genetic similarities, indicating that they adapted to features common in the urban environment.

As a next step, the researchers plan to compare stable isotopes in ants to look at dietary changes, how they might relate to natural versus urban environments, and potential contributing factors such as temperature and the urban heat island effect.

Fargo said researchers have hypotheses but no data yet linking how and why the changes occurred.

The research was started by Blumenfeld, who was a doctoral student in Vargo’s lab and is now a postdoctoral researcher at Yale University. He said he was interested in answering questions about adaptive evolution in animals regardless of taxonomy or species, and whether they were invasive or adapted to human-caused disturbances, including cities.

“The study highlights the impact of urbanization on the evolutionary path of a species,” he said. “It’s important for us to answer questions about adaptive evolution, whether it’s an invasive species or a forest species adapting to city environments.”

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