The taxonomy of Alosa caspia (Clupeidae: Alosinae), using molecular and morphometric specifications, in the South Caspian Sea

Abstract In this paper, classification of subspecies of Alosa caspia (Eichwald, 1838) was examined using morphometric and molecular methods. Preliminarily, four groups of Alosa caspia were identified based on morphometric analyses of specimens taken from the south Caspian Sea. Based on molecular analyses, two of three clades created in a phylogenetic tree with different sequences encoding a certain type of protein were found; therefore, it was assumed that Alosa caspia had no subspecies in the south Caspian Sea. Specimens obtained from different sites were placed in similar clades, which is in contradiction with the idea that the members of each subspecies belong to a separate geographic region. Our morphological results confirm the existence of three subspecies of Alosa caspia, while the phylogenetic analysis based on the cytochrome b oxidase gene does not support the traditionally morphological subdivision of Alosa caspia into three subspecies. The phenotypic differences in the specimens can be generalized to the effect of their different environmental conditions, and from the molecular results it can be concluded that this species does not have any subspecies. Indeed, the selected fragment of cytochrome b was not able to separate the studied groups from one another. It seems, according to these results, that the specimens studied were populations of Alosa caspia species in the south Caspian Sea