Understanding how the spatial and temporal dynamics of populations vary across the landscape is fundamentally important to managing and conserving species. For example, populations may fluctuate in synchrony, or exhibit other forms of spatial sub-structuring, due to intrinsic population parameters or to influences from environmental factors. Importantly, synchronous populations may be at greater risk of extinction if all populations are decreasing to zero at the same time, thereby reducing rescue through colonisation. Different species may not have similar dynamics, even if they share the same environment and thus unravelling the spatial dynamics of multiple species provides vital information about what scale to apply management actions.
Using long-term data (17‑22 years) across a large-scale study region (8000 km2) in arid central Australia, we test for regional synchrony in a population driver, annual rainfall, across nine sites (>20 km apart). We then draw from examples from small mammal and reptile populations and investigate if each species exhibits synchrony. For species that did not exhibit synchrony, we used multivariate autoregressive state-space (MARSS) models to explore four other sub-population structures. We also use the MARSS models to identify important drivers that may regulate populations of these species.
We show that species exhibited different spatial population structuring and respond to extrinsic factors in different ways. We conclude that investigating how the spatial connections among populations interact with their temporal dynamics and eventual persistence or decline, is important for determining the appropriate scale to implement management actions and that “one size does not fit all”.
More on population dynamics of small mammals, MARSS models and Moran: