Fig. 1

Desaturation index of fatty acids as a function of latitude for mammals inhabiting different environments. Dashed (non-significant correlation) and solid (significant correlation) lines indicate the phylogenetic generalised least squares (PGLS) regression lines for: a fully-aquatic (y = 0.02(x) + 2.27; n = 14); b semi-aquatic (y = 0.06(x) − 1.34; n = 25); and c terrestrial mammals (y =  − 0.01(x) + 1.62; n = 15). Only the blubber of semi-aquatic mammals displayed significantly (CIs = 0.02, 0.11) higher fatty acid desaturation when living in colder latitudes. Silhouettes are listed in the same order as they appear in each plot, from left to right and top to bottom. Scientific names can be found in Additional file 1: Table S1