A single gene key to an entire ecosystem
More than 50 years ago, on the coast of a rocky tidal basin, US ecologist Robert Paine found out that the structure and function of an ecosystem can change dramatically if just one species is removed. With the tidal basin, it was starfish which acted as a keystone species. Only their presence and their role as top predators in the rocky ecosystem’s food chain maintained the co-existence of various species.
Mini-ecosystems put to the test
But there is even more specialisation. A team headed by the University of Zurich/Switzerland, have discovered that just a mutation in a single gene can already dramatically change the structure and functioning of an ecosystem. They had examined an experimental ecosystem in the laboratory for their study. It involved thale cress (Arabidopsis thaliana), a commonly used model plant, as the basis of the food network. The next level was formed by the herbivores, represented by two aphid species. Then came the predator, the parasitic wasp Diaeretiella rapae, whose larvae mature in the aphids, in the course of which the latter are killed.
In the experiment, Barbour and his colleagues now examined how the balance of this mini-ecosystem changed as the plant’s hereditary matter was manipulated. For this purpose, in different experimental approaches, they respectively deactivated one of three genes responsible for the chemical repellent glucosinolate and tested how the mutant plants, either individually or together, affected the aphids and their parasites.
It turned out that artificial mutation of just one gene was enough to fundamentally influence the little ecosystem. Depending on which gene was modified, the aphids died off, as did the aphid wasp subsequently as a result, or relationships between the two competing species were transformed.
Here, the modification of one particular gene proved to be particularly favourable. “Not only did this mutation in the AOP2 gene influence the plant’s chemistry, it also helped it to grow faster,” Barbour reports. “This in turn promoted the coexistence of herbivores and predators, preventing the collapse of the ecosystem.”
Thus AOP2 acted as a keystone gene for the experimental ecosystem as a whole and influenced the survival of interacting species in the entire food chain.
The scientists believe that this underscores just how fragile the balance of ecosystems can be. “Only now are we beginning to understand the consequences of genetic modifications for the interaction and coexistence of species,” says Barbour.
“Our results show that the current loss of genetic diversity can have cascade-like impacts resulting in abrupt and catastrophic changes in the continued existence and functioning of terrestrial ecosystems.”
This article first appeared at www.wissenschaft.de (©wissenschaft.de - Nadja Podbregar).