Geographic differentiation in the freshwater crab Potamon persicum Pretzmann, 1962 (Decapoda, Potamidae) in the Zagros Mountains: evidence from morphometry

The freshwater crab Potamon persicum Pretzmann, 1962 in Iran is distributed along the western ­Alborz Mountains, its range extending southeast through the whole Zagros Mountains. We expected a high geographic differentiation within Potamon persicum between the main drainage systems in the region (Khalij Fars-Oman, Markazi and Urmia basins). To test this hypothesis, we conducted conventional morphometric and geometric-morphometric analyses. Comparison of males and females between populations of three main drainage systems showed significant differences of eleven traits. We also detected significant sex-specific differences among the three main drainage systems. The results are supported by geometric-morphometric analysis of the carapace shape, as carapace shape varies between sex and populations of three main drainage systems. Based on both analyses, populations of Khalij Fars-Oman and Markazi basins are similar to each other. Furthermore, a higher differentiation was seen between populations from Markazi and Urmia basins. We hypothesize that the P. persicum geographic differentiation is a result of both isolation by topography and climate during the Pleistocene glacial periods.