Is the state of nature fair? Researchers measure how biomass is distributed in microbial communities
The distribution of income and growing inequality are central themes in public debate. Far less attention has been paid to how resources are distributed in ecological communities, in the so-called state ...
The distribution of income and growing inequality are central themes in public debate. Far less attention has been paid to how resources are distributed in ecological communities, in the so-called state of nature, without any social contract. Species abundance distributions have been studied extensively in ecology, but descriptively. They largely follow a distribution similar to human wealth. Yet the fairness of that distribution has rarely been examined.
Teemu Kuosmanen, a researcher in computer science and organismal and evolutionary biology at the University of Helsinki, has explored the question with microbes as part of the Finnish Multidisciplinary Center of Excellence in Antimicrobial Resistance Research (FiMAR). The study, published in PLOS Biology, examined whether the biomass of a microbial community is distributed among species meritocratically, that is, according to how much each species actually contributes to the community.
"In economics, free competition, which natural selection embodies, is generally thought to lead to an efficient and meritocratic outcome. But we have practically no idea whether the state of nature is a fair and meritocratic place," Kuosmanen says.
The environment affected the fairness of microbial growth
The study assembled 14 microbial communities, each containing four bacterial species. The communities were grown in four different environments: favorable control conditions and more challenging conditions under three different antibiotics. The microbes were left to grow until the community reached equilibrium, after which the researchers measured what proportion of the biomass each species obtained.
A species' contribution is not measured in isolation but in relation to how the whole community grows. This way, synergies among species are also taken into account. Some species may, for example, produce public goods that break down antibiotics and thereby enable other species to grow as well. Others may directly hinder the growth of others and so lower the community's total output.
Some communities distributed their growth in a highly meritocratic way, while others were systematically unfair. Some communities were fair only in certain environments.
In the strongest antibiotic environment, the biomass accumulated almost entirely in a single key species. The fairness of a distribution cannot, however, be inferred directly from the realized distribution: Both evenly and very unevenly distributed communities could be fair.
"Overall, though, we found that the realized ecological distribution was more unequal than the corresponding, fully meritocratic distribution."
How is fairness calculated?
The fairness measure chosen was the Shapley value, a concept from game theory. Developed in economics, the Shapley value is a widely accepted solution for how a shared output or shared costs should be divided fairly among the parties. The Shapley distribution can be shown to be the only one that satisfies certain mathematical axioms of fairness.
Computing the Shapley value is often difficult in practice, however, because the contribution of the same member can differ depending on the community and the environment. Its value depends on the context in which it is measured, just as a person may make a large contribution in one community and a small one in another.
To determine a fair distribution, a community's growth therefore has to be measured in all subcommunities, as was done in this experiment.
Unfairness may be explained by historical dependencies
A community's earlier stages and differences in the starting situation can also affect the outcome. It is known, for example, that different microbial species need slightly different amounts of time to adjust before they can grow in a new environment. This is called the lag phase.
"We noticed that species with a short lag phase generally received the fair share matching their contribution. Species with a longer lag phase, in turn, either suffered or benefited from the fact that some other species were able to grow before them. In this way, various historical dependencies can sustain unfairness even when the distribution mechanism itself is fair."
Can the study draw any conclusions about whether the state of nature is fair?
"The result can be seen as a new opening, made with randomly assembled communities. The Shapley value helps examine fairness precisely because it gives each species a single objective share according to how much it truly contributes to the community's growth. It is possible that nature's own communities are even fairer than this experiment suggests."
Publication details
Teemu Kuosmanen et al, Normative assembly rule reveals fairness in microbial communities, PLOS Biology (2026). DOI: 10.1371/journal.pbio.3003872
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Citation: Is the state of nature fair? Researchers measure how biomass is distributed in microbial communities (2026, July 8) retrieved 13 July 2026 from https://phys.org/news/2026-07-state-nature-fair-biomass-microbial.html
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