SALAMANDRA 57(1): 174–179 SALAMANDRA 15 February 2021 ISSN 0036–3375 Correspondence German Journal of Herpetology Correspondence Aliens in the Netherlands: local genetic pollution of barred grass snakes (Squamata: Serpentes: Natricidae) Marika Asztalos1, Ben Wielstra2,3, Richard P. J. H. Struijk4, Dinçer Ayaz5 & Uwe Fritz1 1) Museum of Zoology (Museum für Tierkunde), Senckenberg Dresden, A. B. Meyer Building, 01156 Dresden, Germany 2) Institute of Biology Leiden, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands 3) Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands 4) Reptile, Amphibian and Fish Conservation Netherlands (RAVON), P.O. Box 1413, 6501 BK Nijmegen, The Netherlands 5) Zoology Section, Department of Biology, Faculty of Science, Ege University, 35100, İzmir, Turkey Corresponding author: Uwe Fritz, e-mail:
[email protected] Manuscript received: 26 November 2020 Accepted: 9 December 2020 by Jörn Köhler Grass snakes are widely distributed across the Palaearctic, being widely distributed across the country (Kabisch ranging from north-western Africa through most of Eu- 1999, de Wijer et al. 2009, Kindler et al. 2017, Stumpel & rope to Central Asia (Mertens & Wermuth 1960, Ka- Janssen 2017). However, mtDNA data revealed that at least bisch 1999). Recent studies based on genetic data rec- three Dutch populations are compromised by alien grass ognize three full species that show limited hybridization snakes (van Riemsdijk et al. 2020, Struijk et al. 2020): in their geographic contact zones: Natrix astreptophora, Alphen aan den Rijn, Krimpenerwaard (both in the prov- N. helvetica, and N. natrix sensu stricto (Pokrant et al. ince of South Holland), and Brunssummerheide (province 2016, Kindler et al.