Journal Article

Redescription, Geographic Variation, and Taxonomic Status of Rio Grande Silvery Minnow, Hybognathus Amarus (Girard, 1856)

URL: https://webapps.usgs.gov/mrgescp/documents/Bestgen-and-Propst-1996.pdf

Date: 1996/01/01

Author(s): Bestgen K.R., Propst D.L.

Publication: Copeia, v. 1996(1), p. 41-55

Abstract:

Hybognathus amarus is redescribed and geographic variation assessed to resolve its taxonomic status. Hybognathus amarus is distinguished from congeners by its small size, ovate cross-section, short basioccipital with a wide and shallowly concave posterior margin, moderate orbit diameter that is less than gape width or snout length, rounded snout, subterminal mouth, lateral band that does not intersect the lateral line, and relatively short intestine. Characters and univariate and multivariate analyses of morphometric variables support recognition of H. amarus as a valid taxon but did not support designation of subspecies for H. amarus from the Rio Grande, New Mexico; the Pecos River, New Mexico; or the lower Rio Grande, Texas. Rather, most geographic variation was at the scale of subsamples within those regions. Comparisons of body size, orbit diameter, gape and body width, body circumferential scale counts, and basioccipital process shape useful for identification of all Hybognathus species are presented. Conservation measures are needed to ensure survival of the formerly widespread and common H. amarus, since it presently occurs only in the middle Rio Grande, New Mexico, which is < 10% of its original range.