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[Background]: Ictalurus is one of the most representative groups of North American freshwater fishes. Although this group has a well-studied fossil record and has been the subject of several morphological and molecular phylogenetic studies, incomplete taxonomic sampling and insufficient taxonomic studies have produced a rather complex classification, along with intricate patterns of evolutionary history in the genus that are considered unresolved and remain under debate., [Results]: Based on four loci and the most comprehensive taxonomic sampling analyzed to date, including currently recognized species, previously synonymized species, undescribed taxa, and poorly studied populations, this study produced a resolved phylogenetic framework that provided plausible species delimitation and an evolutionary time framework for the genus Ictalurus., [Conclusions]: Our phylogenetic hypothesis revealed that Ictalurus comprises at least 13 evolutionary units, partially corroborating the current classification and identifying populations that emerge as putative undescribed taxa. The divergence times of the species indicate that the diversification of Ictalurus dates to the early Oligocene, confirming its status as one of the oldest genera within the family Ictaluridae.

[EN] The distribution and diversification processes of freshwater fishes have been influenced by tecto-volcanic and climatic events that have in turn promoted genesis,destruction, and numerous changes in the drainage networks, leaving complex phylogeographic patterns in the ichthyofauna of highly dynamic regions such as central Mexico. In this study, we evaluated the evolutionary history of the Aztec shiner Aztecula sallaei, which is distributed in currently isolated drainages in the highlands of central Mexico, performing phylogenetic, biogeographic, and phylogeographic analyses using three genes: the mitochondrial cytb and two nuclear genes, S7 and ACTB.The studied populations show three genetically divergent and structured lineages: two are exclusive to the Panuco biogeographic region and the third is widely distributed in the Upper Lerma, Middle Lerma, Cuitzeo, and Balsas (Zempoala Lakes) biogeographic regions, as well as one population in Panuco. This widely distributed lineage also presents a genetic structure that is congruent with these biogeographic regions supported by the cytb gene and partially supported by the S7 gene. The divergence time of these lineages was dated to the Pleistocene period (0.56¿2.79 Mya) and was associated with temporally or spatially independent events of river capture, which promoted the exchange of fishes between the river headwaters followed by subsequent isolation, explaining the current distribution of this cyprinid in neighboring but currently isolated basins. Our results indicate that, in the highlands of central Mexico, tecto-volcanic activity has shaped the geographic ranges, diversification, and phylogeographic patterns of freshwater fishes., [ES] La distribución y diversificación de los peces dulceacuícolas han sido influenciadas por eventos tecto-volcánicos y climáticos que han ocasionado numerosos cambios en las redes hidrológicas, dejando patrones filogeográficos complejos en la ictiofauna de regiones altamente dinámicas como el centro de México. En este estudio evaluamos la historia evolutiva de la Carpita Azteca Aztecula sallaei, la cual está distribuida en las tierras altas del centro de México, para lo cual realizamos análisis filogenéticos, biogeográficos y filogeográficos utilizando tres genes, el mitocondrial cytb y dos genes nucleares, S7 y ACTB. Nuestros hallazgos mostraron que las poblaciones estudiadas de A. sallaei constituyen tres linajes genéticamente divergentes y estructurados, dos de ellos exclusivos de la región biogeográfica del Pánuco y el tercero ampliamente distribuido en las regiones biogeográficas de Alto Lerma, Medio Lerma, Cuitzeo y Balsas (Lagos de Zempoala), incluyendo también una población del Pánuco. Además, este linaje ampliamente distribuido muestra una estructura genética congruente con estas regiones biogeográficas soportada por el cytb, y parcialmente por el S7. El tiempo de divergencia de estos linajes fue fechado durante el periodo Pleistoceno (0.56–2.79 Ma) y está asociado a eventos de captura de ríos ocurridos independientemente en tiempo o espacio geográfico. Estos eventos promovieron el intercambio y posteriormente el aislamiento de los peces en las cabeceras de los ríos, lo que explica la distribucion de este ciprínido en cuencas vecinas, pero actualmente aisladas. Nuestros resultados apoyan que la actividad tecto-volcánica en las tierras altas del centro de México ha moldeado la distribución geográfica, diversificación y los patrones filogeográficos de los peces dulceacuícolas.