Why are there so many different species? For biodiversity, chaos plays a crucial role
Scientists from the University of Cologne and the University of Osnabrück have shown for the first time that in biological systems with a single species, chaotic, unpredictable dynamics can happen even when the outside conditions are completely stable. Even without interactions with the environment or other species, these kinds of changes happen, like when the number of individuals in a population goes up and down.
This could be the reason why there are so many different kinds of species on our planet. If, contrary to what was thought before, different species and evolutionary lineages have their own irregular chaotic dynamics, they will never meet each other with the same number of individuals at the same time. Since there is less direct competition between species, they can live together and change for a much longer time. The Proceedings of the National Academy of Sciences has published this study (PNAS).
Biodiversity is all the different kinds of life, from genes to whole ecosystems. It includes the processes of evolution, ecology, and culture. It’s not just about species we think are rare, threatened, or endangered. It’s about all living things, from humans to microorganisms, fungi, and small invertebrates that we don’t know much about.
Biodiversity is important to all of us. In addition to keeping our environment stable, it helps us meet many of our basic needs, like food, energy, and sources for medicines. Biodiversity is also important for pollination, spreading seeds, and getting rid of pests in agriculture.
Climate regulation needs a lot of different kinds of life. A lot of different kinds of organisms are also needed for nutrient cycles and purification of drinking water and waste water. People are destroying biodiversity at an alarming rate right now. One-fourth of all species are thought to be in danger.
In this study, the research group of Professor Dr. Hartmut Arndt at the University of Cologne’s Institute of Zoology looked into the factors that have led to the diversity of species on Earth and what we need to do to keep these factors working. Arndt and his team have been looking at how different species live together as a model for how evolution works in model organisms for a long time.
Scientists have shown for the first time, using lab experiments and model data, that uneven changes in the number of individuals in a population can have a big effect on how well species can live together, even at the level of a single cell type without any outside forces. Changes in population density and deterministic chaos, which looks like chaos but is actually caused by predictable factors, have been talked about for decades as important factors in the number of species in natural biological systems.
Johannes Werner and Tobias Pietsch, two doctoral researchers on Arndt’s team, have now shown that, contrary to what other researchers thought, systems with only one species in a continuous flow of nutrient medium have dynamics that are not simple, even showing signs of deterministic chaos.
That is, changes in the number of individuals can happen even when conditions are pretty stable and there are no interactions between different species or changes in the environment. With the help of theorist Frank Hilker at the University of Osnabrück, a modeling study was done to add to these data. The first author of the study, Johannes Werner, says that the simple, general model they made to study the cell division cycle shows a wide range of dynamic behavior.
The observed phenomenon is important for understanding how evolution works because it shows that competing species or cell lineages can live together even though their numbers change. This is a key reason why there is so much variety of life on Earth.
The researchers said that keeping biodiversity and its functions safe requires letting these changes happen. For example, nature reserves should be big enough so that the natural ups and downs in the number of individuals in a species don’t cause them to go extinct. Even when the weather is very bad, individuals should always stay to make sure the species doesn’t go extinct.
Johannes Werner et al. (2022). Intrinsic nonlinear dynamics drive single-species systems, Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2209601119
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