Fig. 4: Expression profiles have coevolved extensively and diverged as much in lower as in upper molars.

a Nested models of temporal profiles taking the four teeth altogether. The percentage of coevolution is computed as a proportion of informative genes varying between species and/or teeth, for different gene categories with numbers into brackets (number of informative genes/total number of genes in the category). Dispensable and keystone gene categories taken from ref.³⁷. Genes from tooth developmental “pathways” (further splitted into individual pathways, blue) and their target genes (red) taken from refs. ⁹⁶. b, c Bmp4 and Wif1’s expression profiles corroborated by in situ hybridization of dental mesenchyme show that expression in upper and lower molar has coevolved. Dashed lines map pictures to the timeseries and numbers in the picture corners are developmental age. Arrows point to regions of the dental mesenchyme with strong expression. See supplementary Fig. 5 for details. d (grey dots), and models (curves). Top: the “upper divergent” model, allowing different profiles in mouse and hamster (green), is compared with the “upper non-divergent” fitting the same profile but different baseline expression levels (grey). Bottom: Same models fitted independently for lower molars (purple and grey). Best model was chosen for each molar by likelihood ratio test (adjusted p < 0.05). Barplots: percentage of divergent profiles in upper and in lower molars (categories as in a). e. Percentage of the “divergent” genes detected in d, found both in upper and in lower molars (yellow), only in upper (green) or only in lower (purple).