New records of cave-dwelling populations of Rhamdia catfishes (Siluriformes, Heptapteridae) from Chiapas, Mexico

Dedicated ichthyological surveys in four active karstic caves the Mexican state of Chiapas (Grijalva River drainage basin) resulted discovery same number hypogean populations Rhamdia catfishes assignable to two different species: R. laticauda and guatemalensis . The taxonomic identity these was initially determined based on morphological traits subsequently corroborated with molecular data a phylogenetic framework. For most part, newly discovered exhibit partial variable troglomorphism (vs. fixed), pattern that has been observed other cave-dwelling species/populations , possibly caused by gene flow and/or incipient speciation from epigean lineages. Since forms derive from/are part larger clade, our is noteworthy includes very first record population pronounced widespread troglomorphism. Our hitherto unrecorded highlights continued importance exploration process documenting subterranean biodiversity, particularly regions world rich cave systems. findings corroborate notion that, among Neotropical fishes, catfish genus one prone effective at colonizing habitats establishing viable populations.