N 1917, biologist A. G. Tansley performed a famous series of studies on two species of bedstraw, a plant that was used to stuff beds. In nature, heath bedstraw is confined to acidic soils, while slender bedstraw lives on calcareous soils. From one set of studies, Tansley knew that each species could exist on both types of soils. This led him to wonder if competition between the two species was responsible for their non-overlapping distributions. To answer this question, which of the following is the best approach