Habitat-associated morphological divergence in four Shemaya, Alburnus chalcoides (Actinopterygii: Cyprinidae) populations in the southern Caspian Sea using geometric morphometrics analysis

In this study, Geometric morphometrics approach was used to explore body shape variations and growth trajectory among four population of Shemaya (Alburnus chalcoides). The shape of 114 individuals from three rivers (Lisar, Shiroud and Babolroud) and one lagoon (Anzali) from the south of Caspian Sea was extracted by recording the 2-D coordinates of 16 landmark points. We applied a GPA analysis to eliminate non-shape variations. PCA, CVA, MANOVA analysis were used to examine shape differences among populations. The significant differences found among the shape of populations. Since Shemaya is an anaderemus fish and all their populations have a common origin, we concluded that differences between habitat features might create selective pressures resulting morphological divergence among conspecific populations. We suggest that high level of plasticity, particularly in the depth of body, head and caudal peduncle shape may reflect low costs of maintaining the plastic response even in relatively isolated populations.