Characteristic habitats and sampling sites along the Hungarian section of the River Maros. (A) General appearance in summer. (B) Characteristic view in summer with a typical sand reef in the middle of the river. (C)–(E) Typical habitats for Pontogammarus robustoides indicated with red arrows. (C) Riparian woody vegetation hanging into the water, location #12 at Makó in spring, this site provided the three specimens barcoded for this study. (D) Anchored woody debris and garbage, location #21 at Szeged in summer. (E) Littoral shrubs hanging into the water, location #18 at Maroslele in summer. (F) Stony embankment, location #08 at Magyarcsanád in summer (photo credits: Arnold Móra).