BACKGROUND: The central thesis of plant ecology is that climate determines the distribution of global vegetation. Within a vegetation type, however, finer-scale environmental features such as the physical and chemical properties of soil (edaphic variation) control plant distributions and diversity patterns.

AIMS: Here, we review the literature to provide a mechanistic framework for the edaphic control of plant diversity. First, we review three examples where soils have known, prevalent effects on plant diversity: during soil formation, on unusual soils, and in regions with high edaphic heterogeneity. Second, we synthesize how edaphic factors mediate the relative importance of the four key processes of community assembly (speciation, ecological drift, dispersal, and niche selection). Third, we review the potential effects of climate change in edaphically heterogeneous regions. Finally, we outline key knowledge gaps for understanding the edaphic control of plant diversity. In our review, we emphasize floras of unusual edaphic areas (i.e., serpentine, limestone, granite), as these areas disproportionately contribute to the world’s biodiversity hotspots.

TAXA: Terrestrial plants

LOCATION: Global

CONCLUSION: Edaphic variation is a key driver of biodiversity patterns and influences the relative importance of speciation, dispersal, ecological drift, niche selection, and interactions among these processes. Research is still needed to better understand the underlying mechanisms by which edaphic variation influences these community assembly processes, and unusual soils provide excellent natural systems for such tests. Furthermore, incorporating edaphic variation into climate change research will help increase the predictive power of species distribution models, help identify potential climate refugia, and help identify species with adaptations that buffer them from climate change.

Global distribution of serpentine outcrops compiled from Brooks (1987); Roberts & Proctor (1992), and other published studies. For some locations, the landmark represents the closest named geographical location (e.g., province, municipality, etc.).