Fig. 8

Phylogenetic strain-space of total maximum in-plane principal strain of bird lower jaw finite element models in this study. Grey lines indicate phylogenetic relationships. Contour plots for selected taxa are provided for reference. Results are visualised with PCA (A, B) and LDA (C, D), excluding (A, C) and including (B, D) semi-specialists. Results are obtained using the intervals method [34] where the percentage of model area under intervals of strain are treated as variables for multivariate analysis. Seventy five intervals were used for PCA and LDA. In PCA (A, B), overall strain increases along PC1 and unevenness of strain distribution increases along PC2. In LDA (C, D), LD1 and LD2 have loadings made of various low-strain intervals, with high-strain intervals clustering near the origin. See Additional file 1: Fig. S5 for precise character loadings. Diet abbreviations: FrugivoreH hard frugivore, FrugivoreS soft frugivore, GranivoreS swallowing granivore, GranivoreH husking granivore, InvertivoreH hard invertivore, InvertivoreM medium invertivore, InvertivoreS soft invertivore, Tetra Hunt tetrapod hunter. Taxon abbreviations: Lr Longirostravis, LxL large-toothed Longipteryx, LxS small-toothed Longipteryx, Rp Rapaxavis, Sw Shanweiniao