Morphological Systematics of the Crystal Darter (Crystallaria asprella)

Abstract

Morphological analyses were conducted on preserved specimens of the crystal darter from 12 rivers representing four major river basins: the Ohio River, upper Mississippi River, lower Mississippi River and Gulf Coast drainages. Differences in head depth and caudal peduncle shape were detected among individual river populations, but with no clear pattern other than that there were no within-basin differences. Pooling of populations by major basin revealed that the four systems were all distinct from one another except the upper and lower Mississippi River drainages. Separate analysis of specimens from five extant populations was conducted to compare the results with those of molecular analyses. Morphological results were not as distinct as genetic analyses, but notably, the Elk River population was distinct from three of the four other existing populations. Shape differences in extant populations were restricted to the caudal peduncle region.