On the relationship between spatial environmental variability, dispersion and biodiversity

AimWe establish quantitative relationships between species richness and the rate of spatial change in controlled, digital, environments. We use a simplified, first-principles, stochastic, evolutionary model in which artificial organisms can evolve and disperse. We develop an understanding of how environmental variability in space influences species richness and how it is affected by organisms ability to disperse. Time periodAt each time step of the experiment, each organism can reproduce sexually, disperse and die. Each experiment is run for 100,000 time steps. The life span of each organism is 15 time steps. LocationThe model uses an artificial, digital, landscape consisting of a uniform (x, y) grid of cells, with a single environmental variable that changes sinusoidally in the x direction. Major taxa studiedOrganisms are defined by a 64-bit genome and reproduce sexually. These digital organisms are designed to mimic the basic principles of biological evolution. MethodsEach experiment starts with a single organism, which can mutate and reproduce sexually, producing offspring that can do all of the above and disperse in the environment. Monte Carlo experimentation is used to generate statistical insight into species richness by producing thousands of replicate simulations. ResultsA strong correlation is observed between mean species richness and the rate of spatial change in the environmental variable. This relationship holds true for a wide range of dispersal abilities, but diminishes when dispersal ability is very low. Main ConclusionsWe predict that the rate of change of environmental variables (e.g. the derivative of elevation) is a driver of real-world biodiversity where dispersal is sufficient. Our results suggest that the ability of organisms to disperse plays an important role in determining how biodiversity responds to environmental gradients.