Morphometric and meristic variation within populations of the Mexican Roundtail Chub Gila minacae (Teleostei: Cyprinidae) in Northwest México

Authors: Carlos Ballesteros, Gorgonio Ruiz-Campos, Alejandro Varela-Romero, Sergio Gonzáles

Year: 2019

Abstract

The Mexican Roundtail Chub, Gila minacae, possess a widespread distribution in the Yaqui River basin and other adjacent southward drainages at the Sierra Madre Occidental in northwest México. However, the formal description of G. minacae was based exclusively on specimens taken from the type locality on the Papigochic River at Miñaca, in the Yaqui River basin. Therefore, all the populations currently considered part of the G. minacae lineage and inhabiting the drainages beyond the south of the Yaqui River basin have not been formally characterized in terms of their meristic and morphometric variation. We performed a morphological characterization of populations of the Gila minacae lineage inhabiting the Yaqui River basin, and the southern populations from the Fuerte, Sinaloa, and Culiacán River basins, plus other congeneric species from the Sierra Madre Occidental, Mexico. Discriminant function analysis based on 33 morphometric and six meristic characters applied to 209 Gila spp. specimens revealed 15 body characters to be significantly different (p < 0.01) among the taxa compared. Canonical variables 1 and 2 explained 76.8% of the total variation among the populations analyzed. Morphologically, the southern Gila sp. populations inhabiting the Fuerte, Sinaloa and Culiacán River basins are divergent from both the Gila minacae found in the Yaqui River basin and the other species analyzed. The southern populations of Gila sp. have a deeper body and lower numbers of gill rakers, dorsal fin rays, and lateral line scales than G. minacae from the Yaqui River basin. The morphological differences detected here among populations of G. minacae from the Yaqui River basin and the southern populations suggest the presence of at least two significant evolutionary units within the Gila minacae lineage.