Extinction of Species Has Cascading Effect

The University of Exeter team believes any extinction can create a ripple effect across a food web, with far-reaching consequences for many animals.

According to the study, Published in the Royal Society journal Biology Letters, when a carnivore becomes extinct other predatory species could soon follow. The new findings lay emphasis to growing evidence that a 'single species' approach to conservation is misguided.

To progress with the finding, the researchers bred two species 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.

They noticed that due to the absence of the first wasp species its prey multiplied in number. This threatened the other aphid, which the second wasp species attacks, eventually leading to its extinction. The reason behind this is that, both the types of aphids feed on the same plants. When thrived on the food, eventually it led to lack of food for the other and it the other thrived in the absence of its wasp predator.

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.

"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."