Parasitic 'Vampire' Plants Aren't So Bad, After All

Parasitic "vampire" plants may get a bad rep from their name, but new research shows that they aren't so bad, after all, and that they could actually benefit the abundance and diversity of vegetation and animal life around them.

During the study, a team of researchers including some from the University of Lincoln assessed the impacts of these "vampire" plants on the biodiversity of a species-rich semi-natural grassland. They did so by altering the densities of the hemiparasite (a parasitic plant that also photosynthesises) Rhinanthus minor, located in the Castle Hill National Nature Reserve in Sussex. The scientists compared the plant and invertebrate communities in areas where R. minor was removed, left at natural densities, or increased in abundance.

What they found was that plots with natural and enhanced densities of R. minor had lower plant biomass than plots without the hemiparasite, and in enhanced densities the number of invertebrates nearly doubled.

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 does it benefit other plants, but also detritivores - animals that feed on dead plant and animal matter - herbivores and their predators.

"This was a really unexpected finding. Although hemi-parasites are known to increase the diversity of other plants in the community by suppressing the dominant species they parasitize 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," lead author Professor Sue Hartley, of the Department of Biology at the University of York, said in a news release.

"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," she added.

Prior research has indicated that both sub-dominant species and parasites can have disproportionately large effects on other organisms, and the effects of the vampire plant add to this growing evidence. Hopefully future studies can help scientists better understand the impact of certain species on overall community structure.

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