The cichlid fish of Cuatro Cienegas, Mexico. Direct evidence of conspecificity among distinct trophic morphs.

Abstract

Two discrete cichlid fishes endemic to Cuatro Cienegas differ significantly in several morphological characters associated with feeding specializations. Conventional taxonomic treatment would suggest the presence of 2 distinct species, but the presence of a single polymorphic biological species has been argued. Biochemical comparisons and observations of reproduction revealed gene and genotypic homogeneity between the 2 types of fishes. Of cichlid pairs collected in the process of mating, 57% involved matings between forms, unequivocally suggesting the existence of a single Mendelian population. Trophic polymorphism may represent an alternative strategy to adaptive radiation and may inflate estimates of species diversity based solely on phenetically defined taxa.- from Author