Figure 4.—

The quantitative relationship between the mitochondrial substitution rate of asymmetry δ₁ and the degree of asymmetry in F₁ viability, using node averages. Both relative rate and relative asymmetry are calculated, selecting species 1 for each pair from an arbitrary clade subtending each node, allowing both positive and negative values of each variable. This regression is partially redundant with the sign test described in the text, as it tests for effect direction: this is illustrated by dividing the figure into quadrants (dotted lines). The one node that runs counter to our expectation is indicated by an open rather than a solid circle.