Discovery of Two New Astyanax Cavefish Localities Leads to Further Understanding of the Species Biogeography

Abstract

The Astyanax species complex has two morphs: a blind, depigmented morph which inhabits caves in México and an eyed, pigmented surface-dwelling morph. The eyed morph can also be found in a few caves, sometimes hybridizing with the cave morph. This species complex has arguably become the most prominent model system among cave organisms for the study of evolutionary development and genomics. Before this study, 32 caves were known to be inhabited by the cave morph, 30 of them within the El Abra region. The purpose of this study was to conduct new surveys of the area and to assess some unconfirmed reports of caves presumably inhabited by troglomorphic fish. We describe two new localities, Sótano del Toro #2 and Sótano de La Calera. These two caves comprise a single hydrologic system together with the previously described cave of Sótano del Toro. The system is inhabited by a mixed population of troglomorphic, epigeomorphic, and presumably hybrid fish. Furthermore, Astyanax cavefish and the mysid shrimp Spelaeomysis quinterensis show a phylogeographic convergence that supports the notion that the central Sierra de El Abra is a biogeographical region that has influenced the evolutionary history of its aquatic community across species. The presumptive location of the boundaries of this biogeographical region are identified.

Hybridization underlies localized trait evolution in cavefish

“…The Mexican tetra, Astyanax mexicanus , is a powerful model system for investigating the genetic and evolutionary basis of trait development and behavior 27–31 . Surface populations inhabit rivers from Texas to Mexico and have invaded caves multiple times, resulting in at least 30 populations of cave-morphs in the Sierra de El Abra region of Northeast Mexico 9,32 . At least two independent lineages of surface fish, commonly referred to in the literature as “old” and “new” lineages, have invaded caves within the past roughly 200,000 years 33–37 .…”

“…from Texas to Mexico and have invaded caves multiple times, resulting in at least 30 populations of cave-morphs in the Sierra de El Abra region of Northeast Mexico 9,32 . At least two independent lineages of surface fish, commonly referred to in the literature as "old" and "new" lineages, have invaded caves within the past roughly 200,000 years [33][34][35][36][37] .…”

Hybridization underlies localized trait evolution in cavefish

“…The Mexican tetra, Astyanax mexicanus , is a powerful model system for investigating the genetic and evolutionary basis of development and behavior ( Yoshizawa et al., 2010 ; Duboué et al., 2011 ; Bibliowicz et al., 2013 ; Kowalko et al., 2013 ; Aspirasa et al., 2015 ). Surface populations inhabit rivers from Texas to Mexico and have invaded caves multiple times, resulting in at least 30 populations of cave morphs in the Sierra de El Abra region of Northeast Mexico ( Mitchell et al., 1977 ; Espinasa et al., 2020 ). At least two independent lineages of surface fish have invaded caves within the past ∼200,000 years ( Ornelas-García et al., 2008 ; Herman et al., 2018 ).…”

Divergent evolutionary pathways for aggression and territoriality in Astyanax cavefish

“…Furthermore, the molecular basis of repeated trait evolution can be examined in this species, as multiple cave populations have independently evolved the same traits (Jeffery 2001;Jeffery 2009). Thirty-four caves are currently known to be inhabited by Astyanax (Espinasa et al 2020). They are found in three mountain ranges in Northern México (Sierra de Guatemala, Sierra de El Abra, and Micos), and one mountain range in Southern México (Guerrero; Granadas and La Joya).…”