Figure 4.

Mandible (MAN) shape variation in the Pom × Scan F₂ population. (a) Principal components (PCs) that collectively explain 90% of MAN shape variation. PCs that account for more than 5% of variation are indicated in blue. (b) PCA plots of PC1 versus PC2 (left) and PC1 versus PC3 (right). Founders are highlighted in blue (Scan) and red (Pom), F₂ birds are denoted in black. (c–e) Visualizations of PC1 (c), PC2 (d), and PC3 (e) minimum and maximum shapes in three ways: heatmaps displaying distance from mean shape (left), wireframes showing displacement of landmarks from mean shape (center), and warped meshes (right). For wireframes and meshes, shape changes are magnified to aid visualization: 1.5× for PC1 and PC2, 2× for PC3 [Color figure can be viewed at wileyonlinelibrary.com]