Roberts, G. G. | Search bioRxiv

bioRxiv2024

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.

ecology↗

bioRxiv2022

Scale-Dependent Coherence of Terrestrial Vertebrate Biodiversity with Environment

AimUnderstanding connections between environment and biodiversity is crucial for conservation, identifying causes of ecosystem stress, and predicting population responses to changing environments. Explaining biodiversity requires an understanding of how species richness and environment co-vary across scales. Here, we identify scales and locations at which biodiversity is generated and correlates with environment. LocationFull latitudinal range per continent. Time periodPresent-day. Major taxa studiedTerrestrial vertebrates: all mammals, carnivorans, bats, songbirds, humming-birds, amphibians. MethodsWe describe the use of wavelet power spectra, cross-power and coherence for identifying scale-dependent trends across Earths surface. Spectra reveal scale- and location-dependent coherence between species richness and topography (E), mean annual precipitation (Pn), temperature (Tm) and annual temperature range ({triangleup}T). Results> 97% of species richness of taxa studied is generated at large scales, i.e. wavelengths 103 km, with 30-69% generated at scales 104 km. At these scales, richness tends to be highly coherent and anti-correlated with E and {triangleup}T, and positively correlated with Pn and Tm. Coherence between carnivoran richness and {triangleup}T is low across scales, implying insensitivity to seasonal temperature variations. Conversely, amphibian richness is strongly anti-correlated with {triangleup}T at large scales. At scales 103 km, examined taxa, except carnivorans, show highest richness within the tropics. Terrestrial plateaux exhibit high coherence between carnivorans and E at scales[~] 103 km, consistent with contribution of large-scale tectonic processes to biodiversity. Results are similar across different continents and for global latitudinal averages. Spectral admittance permits derivation of rules-of-thumb relating long-wavelength environmental and species richness trends. Main conclusionsSensitivities of mammal, bird and amphibian populations to environment are highly scale-dependent. At large scales, carnivoran richness is largely independent of temperature and precipitation, whereas amphibian richness correlates strongly with precipitation and temperature, and anti-correlates with temperature range. These results pave the way for spectral-based calibration of models that predict biodiversity response to climate change scenarios.

systems biology↗