One Extinction Leads To Another
August 20, 2012

One Extinction Leads To Another

redOrbit Staff & Wire Reports - Your Universe Online

According to new research, when a carnivore becomes extinct, other predatory species could soon tag along. Other scientists have previously submitted this theory, but a University of Exeter team has now carried out the first experimentation to authenticate it.

According to lead researcher Dr Frank van Veen of the University of Exeter's Centre for Ecology and Conservation, "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.”

The study, published 15 August 2012 in the Royal Society journal Biology Letters, shows how the downfall of one carnivore species can eventually cause another to become extinct. The University of Exeter team believes any extinction can create a wave effect across a food web, with extensive cost for many other animals.

The research adds credence to growing evidence that a 'single species' approach to protection, for example in fisheries management, is misguided. Instead the focus needs to be holistic, encircling species throughout an entire ecosystem.

According to researcher studies, they bred two species of parasitic wasps, along with the two types of aphids on which each wasp solely feeds on. They set up tanks with different combinations of the species and watched them for eight weeks. 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 flourished.

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 stay alive when the other thrived in the nonexistence of its wasp predator.

"Our research highlights the fact that a 'single species' approach to conservation can be ineffective and even counter-productive. For example, protecting cod could lead to increased fishing pressure on other predatory fish which then, by the mechanism we have demonstrated here, could lead to further negative effects on the cod."

The idea came about during a seminar, in which students were challenged to design an experiment that could prove the theory that predators have indirect effects on each other. The experiment was planned by a team of University of Exeter scientists and second-year undergraduate students. 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 in conjunction with their lecturers.