Figure 1From: The complex origin of Astyanax cavefishNumerous geological events have influenced the settlement of Astyanax cavefish in northeastern Mexico. The El Abra Limestone formation materialized from the vast deposition of marine sediment during the mid-Cretaceous Period (A; light blue). The El Abra Limestone gradually became exposed at the surface ~65 MYa (B; brown). Over the course of several millions of years, a vast network of limestone caves evolved in the area of present-day northeastern Mexico. These caves were subsequently invaded by ancestral surface-dwelling Astyanax fish. Surface-dwelling forms migrated northward from South America in two waves. The older wave arrived in Mesoamerica either ~8 MYa, via an incipient land bridge (D; dashed red line) that connected South and North America, or shortly after (D; solid red line) the closure of the Panamanian-Columbian sea barrier ~3.3 MYa (C; purple). This older wave seeded the caves of the El Abra region (Figure 2). A more recent wave of new epigean stock colonized the region ~2.1 MYa (E; green) and seeded the northern Guatemala caves and the western Micos caves (Figure 2).Back to article page