Systematics of the Cyprinid Fish Notropis amoenus, with Comments on the Subgenus Notropis

Abstract

Notropis amoenus (Abbott) is redescribed and a detailed synonymy presented. Comments are made regarding its nomenclature, type-specimens, and habitat. Sixteen meristic and 10 morphometric characters show no regular pattern of geographic variation and no subspecies are recognized. The most variable meristic character is predorsal scale size; specimens with small, irregularly-arranged predorsal scales become progressively more frequent in northern populations. Mandible and snout lengths are generally shorter in northern populations, complicating the separation of N. amoenus from the closely related Notropis atherinoides Rafinesque. Sexual dimorphism in N. amoenus is weakly developed and confined chiefly to tuberculation differences, which are described. Breeding individuals show no chromatic coloration. N. amoenus is compared with similar and related species. It is specifically distinct from and distantly related to Notropis rubellus (Agassiz), a sympatric and often confused species. Notropis photogenis (Cope) differs from N. amoenus in possessing nine pelvic fin rays, an extremely rare feature in the genus. N. atherinoides is the closest relative of N. amoenus; distinguishing characters are scale counts, head proportions, and trophic modifications. The two species are largely allopatric, but their ranges overlap or come into proximity in New York. The ranges of N. amoenus and central and southeastern New York N. atherinoides are plotted, and their postglacial zoogeography discussed. The dispersal of both species has been influenced by man. N. amoenus is assigned to the subgenus Notropis Rafinesque, and problems within this group are discussed. The subgenus is divisible into two sections on the basis of breeding coloration and pectoral fin tuberculation. The N. rubellus group exhibits chromatic breeding colors. The first ray of the pectoral fin is nontuberculate and following rays bear a single file of large tubercles, a single tubercle occupying each ray segment. This group has no close relative among species currently assigned to the subgenus, and may be related to some species currently classified in the subgenus Hydrophlox Jordan and Brayton. The N. atherinoides group (which includes N. amoenus) and species commonly classified near it are characterized by the absence of chromatic breeding colors. The first ray of the pectoral fin is tuberculate and the following rays bear small tubercles arranged bi- or multiserially, with