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Scientists prove one extinction leads to another

The journal Biology Letters has published an interesting study today about the “ripple effect” across a food chain of one species going extinct.

Scientists at the UK’s Exeter University say an experiment they carried out with parasitic wasps proves that the extinction of one predator can indirectly lead to that of another, with far-reaching consequences across an ecosystem.

A statement from the university explained the experiment, which they say is the first to substantiate a theory which undermines the “single species” approach to conservation:

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.

Lead researcher Dr Frank van Veen said that, while the study focused on insects, the principle would be the same for all carnivores and warned against a narrow approach to conservation in areas like fisheries management. “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.”

A more “holistic” preservation strategy, which encompasses species across an ecosystem, is needed for effective conservation, the team said.

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