Figure 16.5 Tansley’s bedstraw experiment. White bedstraw naturally lives in alkaline soils and heath bedstraw naturally lives in acidic soils. Each species was planted either in its preferred soil or in the preferred soil of the other species; each species grew and survived best in its own preferred soil. This experiment showed that although closely related species can be intense competitors, the competition is reduced when competitors evolve to perform best in different habitats.