Butterfly effect in the ecosystem: a single variant of a gene influences the risk of extinction of a community

Experimental ecosystem with one of the aphids that feeds on arabidopsis and the parasitoid that attacks it.Matthias Furler

In a system, a small initial disturbance, through an amplification process, can generate a considerably large effect in the short or medium term.

This concept of chaos theory and dubbed the butterfly effect, can be applied to ecosystems.

An investigation led by Matt Barbour, from the University of Zurich (Switzerland), and published in

, has shown this: the presence in a plant of only one specific allele (each of the alternative forms that the same gene can have) can affect the persistence of species that interact indirectly in a food web and, according to the study, "generate far-reaching consequences in the functioning of terrestrial ecosystems" to the point of influencing the risk of extinction or collapse of a community.

An allele is a variant of how a gene that regulates hereditary conditions is expressed.

In a pea, one allele can determine its green color and another, yellow.

Barbour's research has focused on the natural diversity of alleles in three genes involved in the chemical defense of

, a plant present on five continents and widely used in genetic experimentation.

Research has determined that while two of these genes (

and

) had no clear effects, substituting the non-functional allele for the functional allele in the

gene reduced the rate of extinction of associated insects (aphids or aphids and parasitoids) by almost 30%.

While most studies focus on how genetic information determines the fitness of an organism, this work has opened up a new avenue for studying how a given gene from one species influences the persistence of interspecies interaction in a given species. ecological community.

It is a very important step because, according to the research, the "cascading effects that cause abrupt and catastrophic changes in the structure and function of the food web" are demonstrated.

The study tests the potential of integrating ecological and genetic network analysis tools to predict the consequences of single allele change on biodiversity persistence.

Jordi Bascompte, co-author of the study and the latest Ramón Margalef Prize winner for ecology, highlights that the experimental system is "representative of most food webs in nature given the omnipresence of herbivorous insects and their parasitoids".

"It is shown that genetic diversity makes the food web more stable and that this effect can be mediated by the particular allele of a gene that a plant has."

Conventional studies focus on the genetic selection of plants that are more resistant to certain herbivores.

But this study goes further.

“The importance of this work”, adds Bascompte, “is that it represents one of the few experimental evidences of how a given gene affects entire ecological communities;

it represents a bridge between the molecular scale and the ecological scale and, therefore, helps to better understand the effects of the loss of genetic diversity”.

Barbour explains the cascading effect: "Those plants that possess the specific allele generate a more persistent food chain by increasing the growth rate of both the plant and its herbivores, which also favors the parasitoid."

“The key”, adds Bascompte, “is not to analyze a specific effect on a certain species of insect, but to consider effects that can scale the entire community, that is, that condition biodiversity and how it will respond to anthropogenic influences” .

Genetic variation is the fuel for evolution

Patrik Nosil and Zach Gompert, biologists

It was known that genetic variability ends up affecting an ecological community.

The study is relevant because they have found, according to Bascompte, "an exact causal mechanism, the specific gene, the genetic switch capable of explaining the differences not only in the plant, but in an entire community, where an enormous alteration can be registered."

The finding of this specific mechanism has fundamental implications in the study of ecology.

“On the one hand”, explains the Catalan biologist, “the result tells us that losing genetic diversity could be much worse than we thought, because it affects an issue that no one had talked about, such as the stability of ecological communities.

But, on the other hand, it provides us with opportunities for restoration work because we now know that selecting species with a certain allele would generate a more robust community.

It could be useful to restore habitats degraded by human action”.

"Investigating the impact of specific genetic variants," the study concludes, "has the potential to transform the way we act to conserve genetic and species diversity in a changing world."

Patrik Nosil and Zach Gompert, from the universities of Montpelier and Utah, respectively, point out in a commentary also published in

that the study "demonstrates that a gene that affects the resistance of a plant against herbivores also influences the persistence of the plant." food web through the effect of the gene on plant growth”.

Both biologists, unrelated to the Barbour-led research, believe that "further studies of natural selection in nature may help to understand how

variations may be maintained ."

In this sense, the two scientists highlight how the research proves that only one gene "influences the risk of extinction and collapse of the community in general in the experimental ecosystem", an aspect that they consider fundamental because, as they explain, "genetic variation It is the fuel for evolution.”

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