Citation. Tilman, D. 1997. Distinguishing between the effects of species diversity and species composition. Oikos 80(1):185.   [1585  LTER]

Introduction. Aarssen (1997) raises an important point, with which I agree - that interspecific differences in productivity, combined with the greater probability of having a productive species present in a high diversity plot, may cause productivity to increase with diversity. However, contrary to Aarssen's assertion, this does not mean that the relationship between diversity and productivity reported in Tilman et al. (1996) is an artifact. Rather, three interrelated phenomena - the effects of species diversity, the effects of species composition, and the reasons why diversity or composition have such effects - are being confused.