Morphological diversity of Southern Nase, Chondrostoma regium, populations in the northern catchment sub-basins of the Persian Gulf using geometric morphometric technique

The evolution of fish populations and adaptation to habitat conditions cause morphological differences between them. This study was conducted to investigate morphological variations between Southern Nase, Chondrostoma regium, populations in the sub-basins of the Persian Gulf basin, including the three-border western sub-basins, Karkheh and Karun, using geometric morphometric techniques. For this purpose, samplings were performed from the rivers of Alvand by 18 specimens, 24 from Behesht-Abad, 18 from Beshar (sub-basin of Karun), 14 from Diverab, and 6 from Homeil during 2018-2020. To extract body shape data, the left side of specimens was photographed, and 15 landmark points were digitized on obtained 2D pictures using tpsDig2. The extracted data were analyzed using multivariate analysis, including canonical variates analysis (MANOVA/CVA) and cluster analysis after GPA superimposition. The results revealed a significant difference between the Southern Nase populations of the studied rivers based on the body shape (P<0.05). The main differences in the body shape between the studied populations were in the head shape and size, body depth, snout position, and pectoral fin base. The results indicate the high phenotypic plasticity of this species in diverse habitats.