A paper published last week (full details at the end of this article) proposes a revision to grass snake taxonomy. Researchers based at the Museum für Tierkunde in Dresden, Germany, have been studying the genetics of grass snakes across Europe. Until a few years ago, grass snakes were considered a single species, Natrix natrix, with around 14 subspecies described.

Last year the German group concluded that grass snakes in Iberia and North Africa, previously known as Natrix natrix astreptophora, should be considered a full species, Natrix astreptophora. This latest research proposes that grass snakes in Western Europe – very roughly from Britain east to the River Rhine – should be elevated from the subspecies N. n. helvetica to a newly described full species, N. helvetica. Snakes in much of Italy and some nearby islands, previously known as various subspecies of N. natrix, are also now considered N. helvetica. Grass snakes east of the Rhine are still considered N. natrix.

The conclusions are based on a thorough analysis of the genetic identity of grass snakes sampled across their range, which allowed the identification of contact zones. These can be viewed as a window on the evolutionary process, effectively speciation in action. The data pinpointed a narrow contact zone in the Rhine region, where the two species meet and yet where there is little gene flow. In contrast, further east there is another contact zone between forms currently known as N. n. natrix and N. n. persa, but this contact zone is very wide, with much greater gene flow. This is a complex picture, and it is possible that there will be changes to the taxonomy of central and eastern European grass snakes in due course.

Young grass snake by Jim FosterUnfortunately there were some rather muddled reports in the British media about this research. Some claimed that we had gained a fourth species of native snake, and some made incorrect statements about colouration and markings. For the sake of clarity, since most of these reports appear not to have been corrected, it is worth re-stating that we still have three species of native snake (grass snake, adder and smooth snake). The proposed change is the taxonomic identity of our native grass snakes: along with other Western European grass snakes, researchers argue they should now be referred to as Natrix helvetica, rather than Natrix natrix. The mention of “barred grass snake” in some reports refers to the fact that Western European grass snakes invariably have black bars on the flanks, while this marking tends to be absent in Eastern snakes. Britain also harbours a few populations of non-native grass snakes introduced from the continent, with some snakes exhibiting striped markings, but these are highly restricted and few people encounter them.

Aside from the change in name, this study means that “our” species of grass snake now has a substantially smaller global range. This is important from a pan-European conservation viewpoint, since assigning conservation priorities is, in part, based on range size.

When studies like this are published, other researchers have the chance to examine and challenge the conclusions, if appropriate. Not all such revisions end up being accepted. To take another grass snake example, in the 1980s some researchers proposed that N. natrix in the Caucasus region should be elevated to the new species Natrix megalocephala. That conclusion was not supported by subsequent research, however, and those animals are now once again regarded as N. natrix.

The findings in last week’s paper seem much more solid at first glance. We don’t need to look far to find examples of taxonomic changes that have stood the test of time. European crested newts have undergone substantial revision since the late 1980s, when the various species we recognise today were known as subspecies of Triturus cristatus (having said that, some changes have been proposed in recent years). Research has altered the scientific names and/or taxonomic standing of several other native species. An especially notable finding was that toads on Jersey were recognised (by ARC’s John Wilkinson and colleagues) as belonging to a newly described species, Bufo spinosus, also found on the parts of the continent.

This research highlights one reason why ARC works with colleagues across Europe. Understanding “our” species from a broader perspective can only help conserve them. To this end, we recently founded a new network, Reptile and Amphibian Conservation Europe (RACE), along with NGO partners in Netherlands, France, Germany and Switzerland. Keep an eye on our website for more news on this, or sign up for our e-newsletter here.

The full citation of the grass snake research paper is: 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. DOI:10.1038/s41598-017-07847-9.

You can download it here (open access): http://www.nature.com/articles/s41598-017-07847-9