Systematics of Macrhybopsis tetranema (Cypriniformes: Cyprinidae)
Morphometry, meristic features, pigmentation, and tuberculation were examined from 632 specimens of the Macrhybopsis aestivalis complex from the Arkansas River basin. Patterns of morphological variation support the recognition of two species in the basin: M. hyostoma in the middle and lower portions of the basin in Arkansas, Kansas, and Oklahoma; and M. tetranema in the middle and upper portions of the basin in Colorado, Kansas, New Mexico, Oklahoma, and Texas. Macrhybopsis tetranema is redescribed and compared to M. hyostoma, from which it can be distinguished by longer barbels, smaller eyes, smaller scales, reduced belly squamation, thicker lips, more conical head, and biserial pectoral fin tuberculation. These species are sympatric and maintain their identities in the Cimarron, Salt Fork of Arkansas, and Arkansas Rivers. Morphological intermediacy of M. tetranema in some areas of sympatry may reflect convergent adaptation to local conditions or hybridization with M. hyostoma.
Copeia, Vol. 1999, No. 4 (Dec. 17, 1999), pp. 969-980.