World-First Discovery Finds Plant Has Evolved To Utilize Ants As Pollinators

Ants are poor pollinators for most plants, but one shrub family has outsmarted them. Edith Cowan University

Rachael Funnell 09 Jun 2020, 17:27

Ants are one of the less celebrated creatures in the pollinator hall of fame and a much rarer pollen porter compared to bees, butterflies, and a host of other creatures. Most ants that feed from flowers secrete a fluid that destroys pollen, earning them the reputation as nectar thieves rather than one of botany’s great matchmakers (though some are doing their best to restore grasslands).

A recent discovery shines new light on these tiny animal’s influence on angiosperms, as it was discovered for the first time that a plant has successfully evolved so that its pollen is unaffected by the ant’s clever defenses. The research published in the journal Annals of Botany comes as a surprise as ants are usually considered to be a menace for plants, with the discovery described as “incredibly rare” by the study researchers.

The trait was discovered by Edith Cowan University (ECU) PhD student Nicola Delnevo in a group of shrubs found in the Swan Coastal Plain in Western Australia. Ants are usually considered a menace for flowering plants as they secrete an antimicrobial fluid that destroys the pollen grain. They produce this to stop other pollinating insects from approaching the flower and sapping their resources. However, a group of plants known as the Smokebush family, Conospermum, has adapted a way to use this to their advantage.

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

While there are around 46 examples of ant pollination in the wider world, these interactions have been enabled by ants with less toxic secretions, meaning some of the pollen they were carrying survived. This is the first instance where a plant has been found to have adapted its biochemistry to account for the antimicrobial fluids.

The adaptation is a fortunate one for Smokebush in the area as their tubular flowers are too narrow for honeybees to wriggle inside and they instead are solely reliant on a native bee, Leioproctus conospermi, that has evolved as a specialist feeder of these flowers. In a changing climate, it’s always wise to hedge your bets. By altering their biochemistry so that visiting ants can also ferry their pollen from plant to plant, the Smokebush has increased its chances of survival.

The researchers now want to investigate the flora of southwestern Australia further to see how common this kind of pollination is in the region and trace how this trait of accounting for the ant’s antimicrobial fluids in plant pollen biochemistry came about.

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