Morphological differentiation between two populations of the Shemaya, Chalcalburnus chalcoides: a geometrical morphometric approach

Abstract

Morphological differences (shape and size) among two populations of Shemaya (Danube Bleak), Chalcalburnus chalcoides,were studied by the geometric methods of shape PCA, thin-plate splines and multivariate analysis of partial warp scores. Measurements of Cartesian coordinates of 15 landmarks were obtained from 66 specimens from the Rivers Haraz and Shirud. For each specimen, centroid sizes were computed; sexual dimorphism and variation in size among sites were tested using t-test. Sexes differed significantly in size (P<0.001), with females being larger than males. Populations had significant size differences (P<0.001), with specimens from the River Shirud being larger than those from the River Haraz. Body shapes were significantly different between sexes (P<0.001) and populations (P<0.001), but interaction of sexes at sites were insignificant (P=358). TPS analysis showed a sexual dimorphism of shape, in particular the abdominal area, which appeared to be more enlarged in the females of the two populations. The canonical vitiate analysis CVA based on partial warps correctly identified all female specimens and 95% of male specimens at both locations. The results show thast the difference in body shape between the two populations is probably due to habitat influence (water flow speed).