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Scientists have mathematically modeled the life of microbial communities, explaining how they manage to maintain diversity and stability at the same time. The results of the work are presented in Physical Review Letters, and the preprint of the scientific article can be read for free on the Arxiv website.
For many years, biologists have been unable to unravel the secret of the marine microorganism community and understand how it can be so diverse, while remaining stable. Not only unicellular inhabitants of water bodies can boast of such features, but also microbial communities living in the bodies of large organisms and in other places.
In most of these communities, there are “central” species, which are the most represented, and “peripheral” ones, which are less important. They all compete for one resource or a limited range of resources. According to previous calculations and earlier models, the growth in the size of some populations should be sharp and exponential, which could upset the equilibrium of the entire community. Winning in numbers, some populations must capture most of the resource, depriving others of food on the principle of competitive exclusion. But in reality this does not happen, and the community remains stable. Scientists call this the plankton paradox.
One of the main theories explaining the paradox is based on two main principles. The first is that some bacteria eat the waste and waste that others excrete. Another relies on the fact that newcomers to the community should choose free ecological niches or, better than other members of the community, occupy existing ones.
The researchers created a mathematical simulation of this theory by specifying a set of initial rules. Each member of the community could only consume one type of resource, causing the production of two new types. Scientists also suggested that emerging members of the ecosystem can survive only if they find a niche for themselves, occupying an empty one or learning to better use an already occupied resource.
The model made it possible to create a virtual community where, as in true microbial communities, stability and diversity were maintained. Mathematicians noticed that in the early stages of the development of their virtual ecosystem, sometimes there were general “extinctions”, when new species, more efficiently using the resource, seized power. Then the species that ate the waste of the former "favorites" perished. But over time, the community has become more stable, and such extinctions have become much less common.