Is Garra rezai (Teleostei, Cyprinidae) a species known only from two widely disjunct areas in the Tigris drainage?

Abstract

Garra rezai was recently described from two geographically distant areas in the Tigris drainage: upper Yanarsu River (eastern Türkiye) and Bouein-Sofla Creek (Iran). In the scope of this study, we aimed to ascertain the distribution ranges of G. rezai and its morphologically most similar congener G. rufa in Türkiye by examining 1165 specimens from 73 lots, which were collected between 1957 and 2023 and currently curated in two broad fish collections. To achieve this, we focused on two important diagnostic morphological characters which distinguish these two species: scales on predorsal mid-line between dorsal-fin origin and nape, and branched dorsal-fin rays. The results revealed that G. rufa is a widely distributed species in the Tigris-Euphrates catchment, while G. rezai is regionally widespread, with populations identified in at least six different regions within the Tigris catchment. Additionally, G. rezai is documented for the first time in the upper Euphrates. Furthermore, we identified the drainage areas where G. rezai co-exists with G. rufa.