Figure 1. Schematic map and localities of cave and Surface populations of the Mexican tetra, Astyanax mexicanus.

Several cave and Surface populations have been described throughout the Sierra de el Abra region of northeastern Mexico (inset). Cave populations in which the brown mutation is either absent (Molino cave) or has not been described (Tinaja cave) are depicted by a black dot. Cave populations in which the brown mutation has been described are denoted by a brown dot, while populations housing the brown mutation and carrying coding mutations in the gene Mc1r are depicted by a red/brown dot. Cave localities in which the brown phenotype is apparent in nature are labeled in green. Most localities do not harbor albinism (e.g., Chica, Curva, Piedras and Sabinos) and therefore, the phenotypic expression of the brown mutation in nature is inferred in these caves. Caves in which albinism has been reported include the Molino, Pachón, Yerbaniz and Japonés populations. Interestingly, of these caves only the Molino cave does not also harbor the brown mutation. While brown individuals have been reported in the Pachón cave [18], the same has not been reported in the literature in fish derived from the albino Yerbaniz/Japonés cave populations. Surface populations of Astyanax are found widely present throughout the rivers and streams of the region. Reports of the brown mutation and map of localities adapted from [4], [16], [18], [88]–[90].