Cave localities of A. mexicanus whose mitochondrial DNA has been analyzed. With larger font and underlined are localities where S. quinterensis were also collected. In red are caves harboring lineage A and in blue those with lineage B for both mtDNA in Astyanax and histone 3 for S. quinterensis. Notice that lineage B is restricted to a small biogeographical zone, circled in blue. A Molino B Caballo Moro C Pachón D Yerbaniz E Japones F Sabinos G Tinaja H Piedras I Curva J Chica K Chiquitita L Rio Subterraneo. (Figure modified from Mitchell et al. 1977).