A new cave population of Astyanax mexicanus from Northern Sierra de El Abra, Tamaulipas, Mexico

The Astyanax genus represents an extraordinary example of phenotypic evolution, being their most extreme examples the blind and depigmented morphs, which have evolved from independent surface-dwelling lineages. Among cave organisms, cavefish is a prominent model system to study regressive evolution. Before this study, 34 populations were known for be inhabited by morph. majority those are distributed in Northeast México, at Sierra Madre Oriental (32 cavefish), three main areas: de Guatemala, El Abra, Micos, two Balsas basin state Guerrero, Mexico. In present we describe new population found 4.5 km Southward Pachón cave, northern Abra limestone. Refugio resurgence with mixed fish different levels troglomorphism, surface fish, resembling other hybrid within Abra. Based on mitochondrial DNA characterization 16S ribosomal sequence, could identify lineage population, was placed closely related “New Lineage”, sharing haplotypes (i.e. Arroyo Lagartos) populations, instead Central (e.g. Tinaja cave). gives additional evidence intricate history system, where migration, drift, selection shaped evolution morphs through episodes mexicanus history.