Effects of brumation duration on the relative tissue sizes. Panels A-D depict the phylogenetic correlations (shown as phylomorphospace plots (Revell 2012)) between the relative masses of (A) brain and body fat, (B) brain and testes, (C) testes and body fat, and (D) testes and hindlimb muscles, respectively, across the 116 species (results in Table S14). The relative tissue masses represent the centered log ratios of the compositional data, and the lines connect the nodes of the underlying phylogeny, indicating that phenotypic correlations are not simply the result of phylogenetic clustering. The correlation coefficients and 95% confidence intervals are indicated. The loadings from a phylogenetic principal component analysis (Revell 2012) on the same variables are also mapped as vectors onto biplots between (E) the first and second or (F) the second and third principal components. In all panels, the point colors reflect the species-specific brumation periods (see legend in panel A). Generally, where brumation was relatively shorter or absent, species also tended to have relatively larger brains, less body fat and smaller testes, respectively, consistent with the univariate analyses (Fig. 2).