Half a century ago on the shoreline of a rocky tide pool, the ecologist Robert Paine discovered something amazing: the removal of a single species from an ecosystem could dramatically alter its structure and functions. In the environment Paine studied, starfish acted as a “keystone species” in that their presence and role as a top predator in that particular region was fundamental for maintaining the balanced co-existence of a variety of species.
In a recent study led by the University of Zurich (UZH) and the University of California, Davis, a team of ecologists and geneticists have found that even the presence or absence of a single gene could act similarly to Paine’s “keystone species.” According to the scientists, a gene not only encodes information that determines an organism’s fitness, but could also have a crucial role in structuring inter-species relationships in an ecological community.
The researchers constructed an experimental ecosystem in the laboratory, consisting of a predator (a parasitic wasp), two herbivores (aphids), and a plant (Arabidopsis thaliana – a genetic model organism often used in laboratory studies). By testing the effect of three plant genes that control chemical defenses against herbivores, the scientists found that the herbivores and the predator were more likely to survive on plants with a mutation at a gene called AOP2.
“This natural mutation at AOP2 not only affected the plant’s chemistry, but also made the plant grow faster, which in turn helped the herbivores and predator coexist, thereby preventing the ecosystem from collapsing,” explained study lead author Matthew Barbour, an evolutionary biologist at UZH. Thus, similarly to a keystone species such as Paine’s starfish, AOP2 acts as a “keystone gene” playing a critical role in maintaining ecosystem integrity.
The discovery of such keystone genes will likely have significant implications on how to conserve biodiversity in a rapidly changing world. In order to foster more diverse and resilient ecosystems, individuals with different variants of a gene or even genetically modified organisms could be added to existing populations.
However, since this study suggests that even small genetic changes could unleash a cascade of unintended and unforeseen consequences for ecosystems. such interventions will be far from straightforward, and should only be conducted after careful analysis of all possible consequences.
“We’re only just beginning to understand the implications of genetic change on how species interact and coexist. Our findings show that the current loss of genetic diversity may have cascading effects that lead to abrupt and catastrophic shifts in the persistence and functioning of terrestrial ecosystems,” concluded Dr. Barbour.
The study is published in the journal Science.