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Tiny ants make a huge contribution to forest regeneration

Woodland ants play an underestimated role in forest regeneration, according to a new study led by Binghamton University. The experts report that ants in the genus Aphaenogaster are powerful seed dispersers that mutually support understory plants such as native wildflowers.

“Not a lot of people have heard of them, but they are the powerhouse of moving seeds and called ‘keystone dispersers,’” explained study lead author Carmela Buono.

The researchers noted that the majority of  North American eastern deciduous forests have regenerated from previous disturbance in the form of clearing for agriculture. In these forests, woodland ants disperse seeds for flowering plants in the forest understory.

Buono said that northeastern North America is one of the major hotspots of ant-plant mutualism, although it also happens in parts of Europe, Australia, South Africa and in northeastern Asia.

“These plants evolved with seeds that have an appendage rich in fats attached to them, and that’s very attractive to woodland ants,” said Buono. “Ants need fats just as much as protein and sugar, and it’s hard to find foods rich in fats in the forest.”

Woodland ants take the fatty seeds to their nests, which are typically found beneath forest litter, inside of logs, or underneath rocks. Here, the seeds are protected from rodents and slugs. After the ants consume the fatty appendages, they disperse the seeds far from where they originated.

“There are so many interesting, intricate parts of this interaction depending on the types of seeds ants prefer, so you can get this beautiful mixing of flower species in forests,” explained Buono.

Compared to old growth forests, there are fewer woodland ants in secondary forests. This is partially due to competition with invasive slugs that are commonly found in regenerated woodlands.

Slugs often prefer forest edges, and secondary forests may be located closer to habitats that slugs prefer, such as open meadows or active farms, said Buono.

“In a large-scale natural experiment (20 sites), we measured seed removal, the abundance of mutualistic partners and other invertebrates interacting with seeds, myrmecochory cover, and diversity, along with ant habitat and forest structure,” wrote the researchers. “We found lower and more variable seed removal in secondary forests compared with remnant forests.”

Overall, the analysis revealed that mutualist abundance was the primary determinant of the variation in seed removal. The researchers conclude that,  in order to restore newer forests to a healthier state, we need to look beyond the trees to the diversity of insects, which play a crucial role in the forest ecosystem.

“Ants are beneficial,” said Buono. “They’re not as charismatic as butterflies or bees that help pollinate flowers, but they are just as important.”

The study is published in the journal Ecology.

By Chrissy Sexton, Editor

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