Box and whisker plots of the bioacoustic characters analysed using ANOVA / Kruskal-Wallis tests, for species of Ptenopus. Numbered characters (numbered as in Methods) and their units are indicated on y-axis labels. Species colours correspond to those on Figure 2 and indicated on the key. Significant differences (according to pairwise post hoc tests) are indicated through homogenous groupings: Species not significantly different in the present character are one group, as indicated by lower-case letters. Species that share the same letters not differing significantly from each other; species with multiple letters are not significantly different from any other species sharing those letters. Approximate divisions between the groups are indicated by dotted lines perpendicular to the y-axis, and the group letters are indicated to the right of each graph.