Investigation of different populations related to Gammarus lordeganensis using geometric morphometric method

The Geometric morphometric method is a novel method in the studying of Amphipoda morphological characters, especially for the discrimination and separation of the different Gammarus species. Hence, this research was conducted to study the different populations related to G. lordeganensis in Chaharmahal va Bakhtiari province using geometric morphometric method. For this purpose, the third epimeron were used to investigate the separation of populations from five different localities, including Barm, Gerdebishe, Sileh and Sardabe Rostamabad springs in Chaharmahal va Bakhtiari province. For better conclusion, G. parthicus from Sarab Abbasabad spring in Markazi province was added to this study. Photographs were taken from the third epidermal plate (Ep3) to extract morphological data. Then, two landmarks and 10 semi-landmarks were digitized on the posterior, anterior and inferior margins of the Ep3 using the TpsDig2 software. After generalized procrustes analysis, landmark data were analyzed using Principal Component Analysis (PCA), Canonical Variate Analysis (CVA) and Cluster Analysis by PAST software. The results showed significant differences among the studied populations in terms of the shape of the third epidermal plate (P<0.001). They were completely separated from each other. The shape of the third epimeral plate is a useful discriminating character for the identification of morphologically similar Gammarus species. According to the results of this study, it could be stated that the other examined populations attributed to G. lordeganensis in this study are not belong to this species, and there are clearly different Gammarus species.