Changing a single gene can affect an entire ecosystem, as researchers found out in a genetic-ecological experiment. In this case, the mutation of just one plant gene changed the survival of several aphid species and their parasites – and in extreme cases led to the collapse of the entire food chain. The effect of this key gene thus underlines how fragile ecosystems can be.
More than fifty years ago, on the shore of a rocky tide pool, US ecologist Robert Paine discovered that the removal of a single species can dramatically alter an ecosystem’s structure and function. In the case of the tide pool, it was starfish that acted as the key species there. Only their presence and their role as top predators in the food chain of the rocky ecosystem maintained the coexistence of different species.
Mini ecosystem under test
But it gets even more specific: a team led by Matthew Barbour from the University of Zurich has discovered that even a mutation in a single gene can dramatically change the structure and function of an ecosystem. For their study, they examined an experimental ecosystem in the laboratory. This consisted of thale cress (Arabidopsis thaliana), a common model plant, as the basis of the food web. The next level was herbivores in the form of two species of aphids, and the predatory parasitic wasp Diaeretiella rapae, whose larvae develop in the aphids and thereby kill them.
As part of the experiment, Barbour and his colleagues now investigated how the balance of this mini-ecosystem changes when the plant’s genome is manipulated. To do this, they deactivated one of three genes responsible for the chemical defense substance glucosinolate in thale cress and used various experimental approaches to test how the mutated plants individually or collectively affected the aphids and their parasites.
One gene – big effect
It turned out that the artificial mutation of just one gene was enough to fundamentally influence the small ecosystem. Depending on which gene was modified, the aphids died off and, as a result, the aphid wasps, or there was a shift in the ratio of the two competing species. The modification of a gene proved to be particularly beneficial: “This mutation in the AOP2 gene not only influenced the chemistry of the plant, but also made it grow faster. This, in turn, encouraged herbivores and predators to coexist, thereby preventing ecosystem collapse,” Barbour reports.
As such, AOP2 acted as a key gene for the entire experimental ecosystem, affecting the persistence of interacting species throughout the food chain. According to the scientists, this underlines how fragile the balance of ecological systems can be: “We are only just beginning to understand the consequences of genetic changes for the interaction and coexistence of species,” says Barbour. “Our results show that the current loss of genetic diversity can have cascading impacts that can lead to abrupt and catastrophic changes in the survival and functioning of terrestrial ecosystems.”
Source: University of Zurich; Specialist article: Science, doi: 10.1126/science.abf2232