Study proves that 1 extinction leads to another

http://www.eurekalert.org/pub_releases/2012-08/uoe-spt081412.php

Public release date: 14-Aug-2012
Contact: Sarah Hoyle
University of Exeter

When a carnivore becomes extinct, other predatory species could soon follow, according to new research. Scientists have previously put forward this theory, but a University of Exeter team has now carried out the first experiment to prove it.

Published today (15 August 2012) in the Royal Society journal Biology Letters, 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 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. 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.

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"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."