A new perspective on evolution: Researchers investigate non-heritable differences

The genes of an organism play an important role in the development of characteristic traits. However, even the traits of genetically identical clones that grow up under the same environmental conditions may differ, for example their body size.

Biologist Lutz Becks and his team from the University of Konstanz will investigate how these non-heritable differences affect the number of offspring of an individual and what role the interaction with other organisms plays in this context.

Just as in humans, in other animals, plants or microorganisms, too, members of the same species differ in their traits. These differences are a key driver of evolutionary change through their effect on the individual's fitness and allow a species to respond to environmental changes in its habitat.

On the one hand, trait variation is the result of genetic differences between individuals—and in this case is heritable. The environment in combination with genetic information, on the other hand, contributes to the trait expression.

"However, some trait variations cannot be explained by genetics or the environment. Even genetically indistinguishable organisms, i.e. clones, that grow up under identical environmental conditions, can show different traits", explains Becks.

Although this intragenotypic variation has been known for some time, it still is fascinating because it contradicts our understanding of evolutionary processes and the fundamental assumption that there is a predictable relationship between the heritable traits of organisms and their biological fitness.

No isolated life

As part of the Momentum project, Becks and his team plan to investigate the phenomenon of "intragenotypic variation" in the context of species interaction as a new aspect.

"As a rule, organisms do not live in isolation from other living beings, neither of their own species nor of others. Much of what we observe in nature is the result of interactions between organisms and the effects this has on their fitness", says Becks.

This fitness ultimately depends on the traits of the two interacting individuals. And this is where intragenotypic variation comes in: In order to predict biological fitness, the intragenotypic variation of both interacting partners has to be taken into account.

The goal of the project is to find out how the interaction with other individuals affects the biological fitness of genetically identical organisms with different traits, so that existing theories in evolutionary biology and ecology can be reconsidered in the light of the project's findings.

Expanding the repertoire of methods

The Konstanz researchers will work with organisms whose trait variations and reproductive success can be easily determined in the laboratory: unicellular microorganisms such as algae or ciliates. In experiments, they will study the biological fitness of these organisms in predator-prey interactions or interactions between competitors for the same resource.

"When describing trait variation, we don't want to limit ourselves to obvious trait differences, such as the size of the organisms, but also look at the results of cell biological processes such as transcription and cell cycle variations", explains Becks.

The modern methods required for this research will be established in Konstanz and applied to the unicellular model organisms. "We assume that intragenotypic variation in combination with species interaction is a previously underestimated component that has far-reaching impacts on the biological fitness of organisms and thus on the dynamics of populations and communities of species.

"Understanding these relationships better is therefore essential for evolutionary research and ecology, and might help, for example, to better understand the existing discrepancy between laboratory studies and those conducted in the field."

Provided by University of Konstanz