Results of additive regression models for three response (Y) variables: the mechanical properties ultimate strength (model a), extensibility (model b) and toughness (model c), and eight predictor (<i>x</i>_<i>i</i>) variables: thread width (<i>x</i>₁), FWHM of the amorphous halo (<i>x</i>₂), FWHM of the (200) diffraction peak (<i>x</i>₃), crystallinity (<i>x</i>₄), long period (<i>x</i>₅), proline composition (<i>x</i>₆), glycine composition (<i>x</i>₇), and alanine composition n (<i>x</i>₈).

These parameters were used because species-specific MANOVAs found them to significantly differ across treatments. Data from all five species studied were pooled to construct the models.