Distribution of Ptomaphagus species on the southern Cumberland Plateau, overlaid on a digital elevation model. Higher elevations (to 500 m) are indicated by darker shades, lower elevations (to 180 m) by lighter shades. Ptomaphagus species diverging early in the South Cumberlands lineage are limited to isolated ridges and mountains on the fringes of the plateau. These species are P. loedingi (yellow), P. longicornis (dark gray), P. julius (blue), P. solanum (dark green) and P. hazelae (light blue). The colors used here correspond to those in Figure 2B.