'Vampire' plants can have positive impact on food chain

LONDON: Parasitic 'vampire' plants that attach onto and derive nutrients from another living plant could benefit the abundance and diversity of surrounding vegetation and animal life, a new study has found.

By altering the densities of the hemiparasite (a parasitic plant that also photosynthesises) Rhinanthus minor, in the Castle Hill National Nature Reserve in Sussex, ecologists from five universities were able to assess the impacts of these 'vampire' plants on the biodiversity of a species-rich semi-natural grassland.

The scientists compared the plant and invertebrate communities in areas where R minor was removed, left at natural densities, or increased in abundance.

The results, published in the journal Ecology, show for the first time the positive effects of a 'vampire' plant further up the food chain - not only on other plants, but also on detritivores (animals feeding on dead plant and animal matter), herbivores and their predators.

"Overall, our findings demonstrate that parasitic plants can have dramatic and lasting impacts on abundance, richness and diversity across multiple trophic levels within semi-natural grassland communities," Dr Libby John, Head of the School of Life Sciences at the University of Lincoln, UK, who was a member of the research team, said.

"Our study provides a clear demonstration of the importance of indirect interactions as major structuring forces in ecology and the strong cascading effects of these interactions across trophic levels," said John.

"Our results also illustrate that keystone species such as R minor can have both negative and positive impacts on other species," John said.

"This was a really unexpected finding," lead author Professor Sue Hartley, of the Department of Biology at the University of York said.

"Although hemi-parasites are known to increase the diversity of other plants in the community by suppressing the dominant species they parasitise and so allowing other plants to flourish, none of us predicted there would be such dramatic and positive impacts on other components of the grassland community," said Hartley.

"R minor increased the abundance of all sorts of animals including snails, woodlice, butterflies, wasps and spiders. This is an important finding for the conservation and management of these chalk grassland communities, which are exceptionally species rich but also rare and threatened," said Hartley.