Some plants have evolved to take advantage of ant pollination

Ant pollination is not very common, and this is likely due to the fact that ants secrete antibiotics that negatively impact plant production. For the first time, experts have identified a plant that has successfully adapted to the antimicrobial substances produced by ants to use them as pollinators. 

Researchers at Edith Cowan University (ECU) discovered a group of shrubs growing on the Swan Coastal Plain in Western Australia that are pollinated by both native bees and ants. 

Study lead author and PhD student Nicola Delnevo explained that ant pollination of plants is incredibly rare.

“Ants secrete an antimicrobial fluid that kills pollen grain. So ants have traditionally been considered to be a menace – nectar thieves whose aggression keeps other potential pollinating insects at bay,” said Delnevo.

“However this group of plants in Western Australia, commonly known as the Smokebush family, has evolved a way to use ants to their advantage.”

The study was focused on six flowering plant species found in Western Australia. The experts tested the effect of the antimicrobial secretion from three local ant species on the plants, and the results were surprising.

“We found evidence that Conospermum plants have adapted the biochemistry of their pollen grains to cope with the antimicrobial properties of the ants,” said Delnevo.

“This is the first plant species found to have adapted traits that enables a mutually beneficial relationship with ants.”

“About 46 examples of ant pollination have been documented around the world, but these have been due to the ants producing less toxic secretions that allow them to pollinate.”

According to Delnevo, the pollination by ants was particularly good news for these plants because honeybee pollination is not entirely reliable.

“Conospermum plants have unscented tubular flowers that are too narrow for honeybees to wriggle inside to pollinate. They rely on native insects carrying a suitable pollen load from visiting other flowers for pollination to occur,” explained Delnevo.

He said that Conospermum plants in this region have co-evolved with a native bee, Leioproctus conospermi. The bee has adapted to become a specialist feeder of these flowers.

“This relationship is mutually beneficial, but it would be risky in an evolutionary sense for the plant to rely solely on the native bee for pollination.”

The researchers want to further investigate the prevalence of ant pollination throughout southwestern Australia. The team also plans to study how the plants  evolved to overcome ant defenses.

The research is published in the journal Annals of Botany.

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By Chrissy Sexton, Earth.com Staff Writer