Morphological analysis of D. b. capito, D. b. fortunei, F1 and backcrossed hybrids. (a) Body measurements used in principal components analysis. HW, head width; HL, head length; TW, thorax width; TL, thorax length; EW, elytron width; EL, elytron length. (b) Means and standard deviations of body-shape scores (PC1 scores) for each of the five populations. The solid line represents the linear regression of mean values.