Scatterplots of PSA results involving productivity attribute reduction: (a) v ₁ = no mean trophic level (TL); (b) v ₂ = attributes in v ₁ and without the intrinsic rate of population growth (r); (c) v ₃ = attributes in v ₂ and without maximum age (A _max); (d) v ₄ = attributes in v ₃ and without natural mortality (M). Species codes are defined in Table 3. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)