Abstract
The blind Mexican tetra fish, Astyanax mexicanus, has become the most influential model for research of cave adapted organisms. Many authors assume that the Sierra de Guatemala populations and the Sierra de El Abra populations are derived from two independent colonizations. This assumption arises in part from biogeography. The 100 m high, 100 m wide Servilleta Canyon of the Boquillas River separates both mountain ranges and is an apparent barrier for troglobite dispersion. Anelpistina quinterensis (Nicoletiidae, Zygentoma, Insecta) is one of the most troglomorphic nicoletiid silverfish insects ever described. 16S rRNA sequences support that this species migrated underground to reach both mountain ranges within less than 12,000 years. Furthermore, literature shows a plethora of aquatic and terrestrial cave restricted species that inhabit both mountain ranges. Thus, the Servilleta canyon has not been an effective biological barrier that prevented underground migration of troglobites between the Sierra de Guatemala and the Sierra de El Abra. The Boquillas River has changed its course throughout time. Caves that in the past connected the two Sierras were only recently geologically truncated by the erosion of the new river course. It is likely that, with the geological changes of the area and throughout the 2-8 million years of evolutionary history of cave Astyanax, there have been opportunities to migrate across the Servilleta canyon.
Highlights
In recent years, the blind Mexican tetra fish Astyanax mexicanus (De Filippi, 1853) has become the most influential model for genomic and evolutionary research of cave adapted organisms
There is great confusion regarding the origin of the 29 populations that inhabit the Sierra de El Abra, Sierra de Guatemala, and Micos mountain ranges in Northeastern Mexico and, if the populations derived from a single or from multiple colonizations
Many current authors embrace the hypothesis that Sierra de Guatemala populations derived from a new epigean stock and that Sierra de El Abra populations derived from an old stock
Summary
The blind Mexican tetra fish Astyanax mexicanus (De Filippi, 1853) has become the most influential model for genomic and evolutionary research of cave adapted organisms. Many current authors embrace the hypothesis that Sierra de Guatemala populations derived from a new epigean stock and that Sierra de El Abra populations derived from an old stock. This is complicated by some El Abra populations, such as the Pachón cave population, having subsequently hybridized with the new stock (Bradic et al 2012). It is seldom assumed that the Guatemala populations could have an old stock origin which has been obscured by extensive hybridization with the new stock, and much less that populations from both mountain ranges could have a single underground cave adapted ancestor. It has been assumed that this 100 m high, 100 m wide canyon has been a biological barrier that prevented underground migration of troglobites between the two karstic areas, and colonization had to occur independently on both mountain ranges
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