Question
Why do some shrublands growing on low-nutrient soils have such rich floras?
Location
Diverse shrublands growing on low-nutrient soils occur around the globe, with examples in the Cape region of Africa, in the Mediterranean basin, and the southwest of Australia.
Methods
This Forum paper discusses and evaluates a hypothesis against the evidence in previously available (but hitherto separated) publications.
Results
Low-nutrient soils create an effective excess of carbon. This makes the production of carbon-based floral rewards relatively cheap. Cheap rewards encourage the use of animal pollinators and this may lead to the generation and maintenance of elevated species-richness in some plant groups, via a number of mechanisms. The literature is used to develop 9 testable predictions of this hypothesis.
Conclusions
The hypothesis discussed here is a plausible and testable explanation for the observed patterns in plant diversity. It is not, however, likely to be the only explanation, and could easily operate alongside several other mechanisms.
