Morphometric and meristic characterization of the endemic Desert chub Gila eremica (Teleostei: Cyprinidae), and its related congeners in Sonora, Mexico

The Desert chub, Gila eremica DeMarais, 1991 is a freshwater fish endemic to Northwest Mexico, being described from the Sonora, Matape and Yaqui River basins in Sonora, Mexico. The recent discovery of 2 isolated small populations from the known distribution for this taxon makes necessary an evaluation to determine their specific taxonomical identities (herein designated as G. cf. eremica). Thirty-three morphometric and 6 meristic characters were evaluated in 219 specimens of several populations of the genus Gila in Sonora, including all the known populations of G. eremica. Morphometric measures based on box-truss protocol were standardized by regression models, and analyzed by means of a discriminant function analysis (DFA). The canonical variables 1 and 2 explained 72.4% of the total variation among analyzed populations. Tree diagram based on squared Mahalanobis distances, as well as scatterplots of centroids, showed G. cf. eremica to be morphologically divergent with respect to known populations of G. eremica as well as the other species analyzed. Box plots indicated a slimmer body and a smaller number of pectoral fin rays, and a higher number of lateral line scales as the most distinguishable characters in G. cf. eremica with respect to nominal G. eremica