On the evolutionary origin of Neotropical cavefish Ancistrus cryptophthalmus (Siluriformes, Loricariidae) based on the mitogenome and genetic structure of cave and surface populations

The evolutionary process of adaptation to the cave environment leads to extreme genetic, morphological, and physiological modifications commonly known as stygomorphism. The cave-dwelling armored catfish Ancistrus cryptophthalmus is a good model to understand the evolutionary processes of stygomorphism in the Neotropics as its ecology and morphology have been studied in detail. Interestingly, it has been found a non-stygomorphic epigean population named Ancistrus sp. This population is morphologically distinct to the hypogean population of A. cryptophthalmus as they present better-developed ocular structures and intense pigmentation. Here we used Illumina sequencing technology to produce partial genome sequences for specimens of Ancistrus sp. and A. cryptophthalmus; we also genotyped molecular markers from individuals of both species. Based on the high level of mitogenome similarity and metapopulation connectivity between the surface and cave populations, we suggest that the evolution of stygomorphisms observed in A. cryptophthalmus may be the result of morphologic modification, by natural selection, of Ancistrus sp. surface population to colonize the harsh cave environment.