Classification Success of Species within theGila robustaComplex Using Morphometric and Meristic Characters—A Reexamination

Abstract

Three cyprinids often referred to as the Gila robusta complex, G. robusta, G. nigra, and G. intermedia, are morphologically similar and genetically indistinguishable at the currently recognized species level. Current taxonomy is based on purported morphometric and meristic differences that are detailed in a classification key; however, the ability of the key to reliably distinguish the species has recently come into question. Chubs were collected from locations in Arizona, and two analysis methods were used to predict species' identification success using the key: 1) correct assignment to species using cluster analysis and multinomial logistic regression; and 2) observer identification success by species. Cluster analysis and multinomial logistic regression correctly assigned only 62% and 74% of fish, respectively, to the assumed species designation. Identification success using both analysis methods was most successful for G. robusta (82% cluster; 82% regression), followed by G. intermedia (53% cluster; ...