Fig. 3

Three hypothetical models of the evolution of cross-sectional morphology in Mustelidae. The phylogeny in A represents a single rate (BM1) or single phenotypic optimum (OU1) process acting across all branches of the phylogeny, both internal and external. The phylogeny in B distinguishes three distinct rates (BM3) or optima (OU3) acting at the terminal branches of the phylogeny, with natatorial, scansorial, and remaining mustelids (i.e., fossorial and generalist taxa) each having their rate/optimum. The phylogeny in C distinguishes four distinct rates (BM4) or optima (OU4) acting at the terminal branches of the phylogeny, one each for the four locomotor habits within Mustelidae. For the BM3/OU3 and BM4/OU4 models, rates and optima acting along internal branches were estimated using stochastic character mapping [8, 45], which reflects uncertainty in character states of internal branches (see main text)