Lack of genetic differentiation between two sympatric lacustrine morpho-species within the Astyanax (Characidae: Teleostei) genus, Mexico

Abstract We analyzed two morpho-species, Astyanax aeneus and caballeroi , coexisting in Lake Catemaco, with ecological differences previously associated different trophic niches. While A. is a widely distributed species, endemic to Catemaco. Due the contrasting morphology between these sympatric they were originally assigned genera, but little known about their genetic differentiation. hypothesized that which present differentiation niches, co-occur concomitance assortative mating form distinct clusters. tested this prediction by typing set of 12 microsatellites 348 individuals comparing structure patterns an allopatric population (i.e., Maquinas population). Genetic analysis, assignment analyses, estimation gene flow morpho-species carried out. Contrary expectations, there lack morpho-species. However, was Catemaco Río populations . In addition, we found asymmetric pattern, larger migration rate from than other direction. Finally, showed lower levels diversity those reported for both lacustrine system. Consequently, our results support notion are either early phase speciation or represent single polymorphic species. This model provides relevant information understanding presence polymorphisms under potential impact on process.