Figure 1.

Relationships between absolute latitude and (a) standard metabolic rate (SMR), (b) mitochondrial respiration, and (c) citrate synthase activity. Data are normalized to measurement temperatures of 20°C (SMR and mitochondrial respiration) or 10°C (citrate synthase activity). Solid lines are the associations between the various traits and latitude from table 3. Because Q₁₀-normalized SMR is positively related to body mass (table 3), and citrate synthase activity is positively related to maximum depth of occurrence (table 3), residuals are presented (i.e. measured – predicted). The best model for SMR included hemisphere of origin (table 3), so SMR data are shown for Northern Hemisphere (filled circles) and Southern Hemisphere (unfilled circles).