Its attractive red berries, succulent leaves and brightly colored flowers might look like a tasty snack for a hungry herbivore.
But while the berries of the bittersweet nightshade already hold enough poison to put off even the most enthusiastic of grazers, it seems the plant also has another trick to defend itself – ant bodyguards.
The bittersweet nightshade, also called Solanum dulcamara, produces a sugary nectar directly from wounds inflicted on its leaves by animals chewing on them in a bid to attract ants.
A poisonous woodland plant called bittersweet nightshade has been found to ‘bled’ a sugary nectar from wounds when slugs and insect larvae eat its leaves. These secretions attract three different species of ant (red ants pictured) which attack the herbivores and protect the plant from suffering further damage
These aggressive insects then attack the hapless herbivores in exchange for the sap-like liquid.
Researchers have found at least three species of ants that forage around the plants are attracted by the leaf wound nectar.
These then drive off creatures such as slugs and beetle larvae that may feed on the plants.
Writing in the journal Nature Plants, Professor Ankie Steppuhn and her colleagues at the Free University Berlin in Germany, said: ‘Plants usually close wounds rapidly to prevent infections and the loss of valuable resources.
‘However, herbivore-inflicted wounds on the bittersweet nightshade Solanum dulcamara appear not to close completely and produce sugary wound secretions visible as droplets.
‘We often observed ants consuming wound secretions from the wound edges and we confirmed in greenhouse experiments that wound secretions attract ants.
‘We reveal that ants can defend Solanum dulcamara from two of its native herbivores – slugs and flea beetle larvae.’
Bittersweet nightshade is widespread in its native Europe and Asia but also grows across much of North America where it is an invasive weed.
