Abstract: Spatial scales can influence our perception of ecological patterns and processes. There was no consensus on the mechanisms underlying the spatial patterns of species richness, largely due to the effects of spatial scales on the explanatory power of different environmental factors and their relative importance in shaping species richness patterns. Topographic heterogeneity is one of the most important factors shaping geographical patterns of species richness. In this review, we discussed the effects of spatial grain and extent on the relationship between topographic heterogeneity and species richness. Although the scaledependence in spatial species richness gradients has become increasingly recognized, it remains unclear how the strength of the relationship between topographic heterogeneity and species richness changes with varying scales of grain and extent. Current studies failed to provide a more complete multiscale picture of spatial patterns in species richness and their drivers. A multiscale perspective with regard to both grain size andextent would shed new light on the studies of topographic heterogeneity-species richness relationships. Further comparative research on geographical patterns of species richness across multiple spatial scales using sound statistical methods and models would improve our understanding of the relative role of topographic heterogeneity at different scales.

Key words: topographic heterogeneity, species richness, biodiversity, spatial scale, grain, extent.