When are bacteria really gazelles? Comparing patchy ecologies with dimensionless numbers.

From micro to planetary scales, spatial heterogeneity-patchiness-is ubiquitous in ecosystems, defining the environments in which organisms move and interact. However, most large-scale models still use spatially averaged 'mean fields' to represent natural populations, while fine-scale spatially explicit models are mostly restricted to particular organisms or systems. In a conceptual paper, Grünbaum (2012, Interface Focus 2: 150-155) introduced a heuristic, based on three dimensionless ratios quantifying movement, reproduction and resource consumption, to characterise patchy ecological interactions and identify when mean-field assumptions are justifiable.

Fear dynamically structures the ocean's pelagic zone.

Fear of predation can have wide-ranging ecological effects. This is especially true in the ocean's pelagic zone, the Earth's largest habitat, where vertical gradients in light and primary productivity force numerous taxa to migrate vertically each night to feed at the surface while minimizing risk from visual predators. Despite its importance and the fact that it is driven by spatial differences in perceived risk, diel vertical migration (DVM) is rarely considered within the "landscape of fear" framework.