Monotonic clines for different orientations. (a) Clines assuming the markers change in the consensus orientation -67.4° from due north. Yellow: Gpd1; pink: Abpa; red: Btk (X chromosome); brown: Mpi; orange: Idh1; purple: Es1; dark blue:Sod1; green: Np; blue: Y chromosome. (b) Monotonic clines for the X marker (red) and uncorrected Y chromosome (dotted blue) assuming the consensus orientation; solid blue line: the corrected Y chromosome cline assuming the marker changes monotonically along its own most likely orientation of change (-28.4° from due north; cf. Table 1). Note that cline centres have been arbitrarily shifted on the x-axis to allow a direct comparison of cline shapes.