The Principle of Optimal Biodiversity and Ecosystem Functioning

We propose the principle of optimal diversity of biosystems. According to this principle, the optimal values of inner diversity of biosystems correspond to their maximum viability (minimum extinction probability). We have investigated a mathematical model of a two-level “population-community” system in a fluctuating environment. The subsystems of the lower level are interpreted as populations while those of the upper level are interpreted as a community of one trophic level made up of these populations. The optimality criteria correspond to the maximum effectiveness of resource utilization by the biosystems, which is possible to consider as an index of ecosystem functioning. Оptimal values of diversity depend on the intensity of resource flow and the instability of the environment. optimal species diversity increases in more stable and “rich” environments, while optimal intrapopulation diversity decreases in more stable environments and is independent of the intensity of resource flow. These opposite reactions allow us to make an assumption of the different roles of intrapopulation diversity and species diversity in a fluctuating environment: intrapopulation diversity is the basis of adaptation to environmental instability, while species diversity enables a community to use resources to the maximum and effectively.In general, the results of our modelling agree with empirical biodiversity patterns, giving us grounds to propose the principle of optimal biodiversity as a working hypothesis complementary to other ideas about interrelation between biodiversity and ecological functioning.