Beta-diversity of geometrid moths from northern Borneo: effects of habitat, time and space.

1. Spatial patterns of beta-diversity, an important property of species communities, are less well-studied than those of local species richness, particularly in insects from tropical rainforests. 2. We use geometrid moth samples from northern Borneo to quantify ensemble turnover across distances of > 700 km, consider habitat- and sampling-related impacts on their composition, and evaluate remaining spatial patterns in the data. 3. Geometrid moth ensembles from Borneo are shaped by environmental parameters such as elevation and habitat disturbance, by temporal factors acting at small (mediated by weather) and large scales (i.e. changes over decades), and by methodological differences of sampling (related to the nightly flight times of species). 4. These parameters explain a large portion of the spatial structure of ensemble composition, but residual variation still contains a pattern that is tentatively best explained by geographical distance, particularly at distances < 20 km. 5. Patterns of species turnover indicate no evidence for biotic homogenization due to human-caused degradation of habitats. Beta-diversity plays a crucial part in mediating the regional diversity of geometrids on Borneo.