A single gene controls species diversity in an ecosystem
More than 50 years ago, on the shore of a rocky tidal pool, American ecologist Robert Paine discovered that eliminating a single species from an ecosystem could dramatically alter its structure and function. He had discovered that starfish act as a keystone species in that their presence and role as top predators kept various species coexisting in the rocky intertidal zone.
Plant defense genes tested with a simplified laboratory ecosystem
A team of ecologists and geneticists from the University of Zurich (UZH) and the University of California at Davis have just discovered that a mutation at the level of a single gene can also significantly alter the structure and function of an ecosystem. The study, published in Science, suggests that a gene not only encodes information that determines the fitness of an organism, but can also influence the persistence of interacting species in an ecological community. The discovery by Jordi Bascompte, a professor in the Department of Evolutionary Biology and Environmental Studies at UZH, and his team was made using an experimental ecosystem in the laboratory with a predator (a parasitic wasp), two herbivores (aphids) and the plant Arabidopsis thaliana — a genetic model organism.
The “Keystone gene” can prevent the collapse of the ecosystem
The researchers tested the effect of three plant genes that control the plant’s natural arsenal of chemical defenses against herbivores. They found that herbivores and predators in their experimental community were more likely to survive on plants with a mutation in a single gene called AOP2. “This natural mutation at AOP2 not only affected plant chemistry, but also accelerated plant growth, which helped herbivores and predators to coexist, preventing ecosystem collapse,” explains Matt Barbour, UZH scientist and first author. Similar to a keystone species such as the starfish, AOP2 acts as a “keystone gene” that is essential for the survival of the experimental ecosystem.
Impacts on current biodiversity conservation
The discovery of a keystone gene will likely have implications for how to conserve biodiversity in a changing world. In particular, knowledge from genetics and ecological networks should be included when predicting the consequences of genetic changes on the persistence of biodiversity at all scales. Individuals with different variants of a gene or even genetically modified organisms could be added to existing populations to foster more diverse and resilient ecosystems. However, a seemingly minor genetic change could trigger a cascade of unintended consequences for ecosystems if not studied in detail beforehand. “We are only beginning to understand the implications of genetic change on how species interact and coexist. Our findings show that the current loss of genetic diversity can have cascading effects that lead to abrupt and catastrophic changes in the persistence and functioning of terrestrial ecosystems,” Barbour explains.