Chromosomal NOR Phenotypes of Seven Species of North American Cyprinidae, with Comments on Cytosystematic Relationships of the Notropis volucellus Species-Group, Opsopoeodus emiliae, and the Genus Pteronotropis

Abstract

Chromosomal NOR phenotypes are documented for seven species of North American cyprinid fishes: Notropis buchanani, N. maculatus, N. stramineus, N. volucellus, Pteronotropis hubbsi, P. signipinnis, and P. welaka. All seven species possessed 2n = 50 chromosomes. Five of the species were found to possess a single pair of NOR-bearing chromosomes. In four of these (N. buchanani, N. maculatus, N. stramineus, and N. volucellus), the single NOR was located terminally on the short arm of a medium-sized submetacentric chromosome; whereas in the fifth (P. hubbsi), the single NOR was located terminally on the short arm of a large-sized acro-/subtelocentric chromosome. Pteronotropis signipinnis and P. welaka each possessed two pair of NOR-bearing chromosomes: one pair had a NOR located terminally on the short arm of a medium-sized submetacentric chromosome; whereas the other pair had a NOR located terminally on the short arm of a large-sized acro-/subtelocentric chromosome. Consideration of these and previous NOR data in North American cyprinids suggest that: 1) the N. volucellus species-group as presently constituted may not be monophyletic; 2) the species Opsopoeodus emiliae may belong in an assemblage which includes, among others, at least four species of the genus Cyprinella; 3) O. emiliae may not be closely related to N. maculatus; and 4) P. hubbsi may belong in an assemblage which includes P. signipinnis and P. welaka, and hence may be a valid member of the genus Pteronotropis.