(a) Parapatric distribution of chromosomal races of the viatica species group in southeastern Australia proposed by White et al. [21,23]. An inset shows distribution of three races on Kangaroo Island. A 100 m isobath is indicated as a proxy of an ancient coastline at glacial maxima during the Pleistocene. Karyotypes of each race (♂)/(♀) are: viatica19, 2n = 19/20, XO/XX; viatica17, 2n = 17/18, XO/XX; P24(XO), 2n = 17/18, XO/XX; P24(XY), 2n = 16, XY/XX; P24(XY)-Translocation, 2n = 16, XY/XX; P25(XO), 2n = 19/20, XO/XX; P25(XY), 2n = 18, XY/XX; P45b(XO), 2n = 19/20, XO/XX; P45b(XY), 2n = 18, XY/XX; P50, 2n = 19/20, XO/XX; V. pichirichi, 2n = 19/20, XO/XX. (b) Thirteen genetic clusters resolved by the Bayesian clustering analysis using 35 allozyme loci, superimposed on a distribution map. Red circles with solid line indicate clusters shared among multiple chromosomal races. Four taxa [P24(XY), P24(XY)-Translocation, P45c, and V. pichirichi] comprise exclusive genetic clusters (blue circles with dashed line).