Trypsin G-banding of North American Cyprinid Chromosomes: Phylogenetic Considerations, Implications for Fish Chromosome Structure, and Chromosomal Polymorphism

Abstract

Trypsin G-banding of chromosomes from North American cyprinid fishes, was used to address phylogenetic problems within the group and to demonstrate the occurence of G-bands which are not differentially rich in AT DNA base pairs. G-band homology of the long arm of the F′, C′, and E′ NOR chromosomes found among six North American cyprinid species, in concert with a hypothesis of species relationships based on morphology, suggests that a NOR situated terminally on the largest chromosome in the complement may represent the plesiomorphic NOR character state within the large “Notropis”-like shiner assemblage. Outgroup comparison suggests that this chromosome may also represent a synapomorphy for the same lineage. Evidence exists which suggests that the F′ NOR is ancestral and that the C′ and E′ NORs are derived. The occurrence in cyprinids of trypsin-induced G-bands which are not differentially rich in AT-/GC-DNA base pairs may indicate that the evolution of trypsin induced G-bands preceded the evolution of differential AT-/GC-richness. The use of trypsin G-banding in cyprinids is expected to permit the identification of previously cryptic chromosomal rearrangements both within and among species. © 1991, Japan Mendel Society, International Society of Cytology. All rights reserved.