The shape of a species' spatial abundance distribution


John Conlisk, 6045 Charae Street, San Diego, CA 92122, USA. E-mail:


Aim  The shape of a species' spatial abundance distribution may change with spatial scale. We predict that the shape will typically change from strictly downward-sloping (falling) to humped (rising then falling) as the spatial scale increases. The prediction, motivated in part by central limit reasoning, is intended for common or abundant species over reasonably homogeneous habitats. We test the prediction using data on 800+ tree species, one ant species, and 14 bird species.

Location  Tree data are for Malaysia and Central America; ant and bird data are for North America.

Methods  For each species, histograms and relative mode shape statistics are compared across multiple spatial scales.

Results  The predicted pattern is broadly confirmed.

Main conclusions  The emerging hump pattern is a candidate for listing among macroecological regularities. In appropriate contexts, spatial theories might be asked to predict the pattern.