With thanks to Rob Ward, University of Kent.
Following on from the recent publication of the scientific paper by Kindler et al., (2017), there have been some misunderstandings about the classification of our native UK grass snake. To clarify:
Until recently, two species of European grass snake were described: Natrix natrix (found across much of Europe, including the UK) and N. astreptophora (found in North Africa and Iberia). These two species are described by Pokrant et al., (2016) – which you can download here
Natrix natrix was further divided into around 14 sub species, with Natrix natrix helvetica – our native UK grass snake, occurring in Britain, France, small parts of Germany, Belgium, Northern Italy, Switzerland and some of the neighbouring countries. Crossing the Rhine in Germany we had Natrix natrix natrix which covered most of central and northern Europe. To the south of Natrix natrix natrix, we had Natrix natrix persa, which extended down in to the Balkans. Italy and some of the other islands (Sardinia, Sicily, Corsica) also contained other subspecies including: Natrix natrix lanzai (Italy), Natrix natrix sicula (Italy including Sicily), Natrix natrix corsa (Corsica) and Natrix natrix cetti (Sardinia).
This has now changed, with the advent of genetic sequencing based on mitochondrial and nuclear microsatellite DNA. This is described in a recent paper by Kindler et al., (2017) – which you can download here.
Everything west of the Rhine in Germany (more or less) is now Natrix helvetica. This includes 'our' grass snake from Britain which is now designated as the subspecies Natrix helvetica helvetica. Together with the four subspecies from Italy and its islands, these are all now considered to be sub species of Natrix helvetica.
We had Natrix natrix helvetica. Now we have Natrix helvetica helvetica. Nothing extra - still only 3 snake species in Britain: one grass snake, the adder (Vipera berus) and the smooth snake (Coronella austriaca).
For more information, the full citations are:
Pokrant, F. Kindler C., Ivanov M., Cheylan M., Geniez P., Böhme W., Fritz U. (2016). Integrative taxonomy provides evidence for the species status of the Ibero-Maghrebian grass snake Natrix astreptophora. Biol. J. Linn. Soc. 118, 873–888.
Kindler, C, Chèvre, M, Ursenbacher, S, Böhme, W, Hille, A, Jablonski, D, Vamberger, M & Fritz, U (2017): Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species. Scientific Reports 7, Article number:7378. DOI:10.1038/s41598-017-07847-9