Cornwall students conduct groundbreaking biology study

Scientists have previously put forward this theory, but the Cornwall-based team has now carried out the first experiment to prove it.

The idea came about during a seminar for second-year undergraduate Conservation and Biology students, led by Dr Frank van Veen. He challenged the students to design an experiment to prove the theory that predators have indirect effects on each other. The students were so inspired by the idea of proving a long-held theory that more than 30 of them volunteered to conduct the experiment with their lecturers.

The researchers bred two species of parasitic wasps, along with the two types of aphids on which each wasp exclusively feeds. They set up tanks with different combinations of the species and observed them for eight weeks. This involved the students doing daily counts of the wasps and aphids to see how numbers were growing or declining.

In tanks that did not include the first species of wasp, the second went extinct within a few generations. In tanks in which they co-existed, both wasp species thrived. In the absence of the first wasp species, its prey grew in numbers. This threatened the other aphid, which the second wasp species attacks, eventually leading to its extinction. Both types of aphids feed on the same plants and there was not enough food for one to survive when the other thrived in the absence of its wasp predator.

The study shows how the demise of one carnivore species can indirectly cause another to become extinct. The University of Exeter team believes any extinction can create a ripple effect across a food web, with far-reaching consequences for many other animals.

The research adds weight to growing evidence that a ‘single species’ approach to conservation, for example in fisheries management, is misguided. Instead the focus needs to be holistic, encompassing species across an entire ecosystem.

The research is now published in the Royal Society journal Biology Letters, which is read by scientists all over the world.

Lead researcher Dr Frank van Veen of the University of Exeter’s Centre for Ecology and Conservation said: “Our experiment provides the first proof of something that biologists have argued for a long time: predators can have indirect effects on each other, to the extent that when one species is lost, the loss of these indirect effects can lead to further extinctions. Although our study focused on insects, the principle would be the same for predators in any ecosystem, ranging from big cats on the African plains to fish in our seas.

“I am really proud of our students, who played such a key role in making the experiment happen, and it’s really exciting to see this research published in a leading journal. This is a great example of when teaching and research can work together to create something exciting and new.”