A new study on the phylogeography of the eastern subspecies of the grass snake (Natrix natrix scutata) has shed light on how this snake species spread across northern Eurasia after the Last Glacial Maximum (LGM). A team of scientists from different organizations led by PhD E.P. Simonov from the Laboratory of Mammalian Microevolution at the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences (IEE RAS) analyzed 135 individuals of the species from 91 locations, studying variations in the mitochondrial cytochrome b gene.
The results showed that most of the modern range of N. n. scutata is occupied by haplotypes from one main haplogroup, which probably originated in the southern regions of European Russia or the North Caucasus. Interestingly, in Western Siberia, only one, the most frequent (ancestral) haplotype was found among 25 individuals studied, indicating a relatively recent colonization of this region. Modeling of the species' distribution showed that during the LGM, there were no suitable conditions for these snakes to live in Siberia and adjacent regions of Central Asia. However, specimens from Transbaikalia have unique haplotypes that differ from the ancestral one by one or two mutations. This suggests that grass snakes could have colonized this region during an earlier interglacial period and survived the last glacial period in this region.
“Increased genetic diversity was also found in the population from the Mugodzhary Range in Kazakhstan, which may indicate the existence of a cryptic refugium in this area as well, but additional research is needed to confirm the hypotheses put forward,” said PhD Evgeny Simonov.
The work was published in the journal Vertebrate Zoology: Simonov E., Lisachov A., Litvinchuk S., Klenina A., Chernigova P., Ruchin A., Bakiev A., Akhmedenov K. (2024) Recent recolonisation of West Siberia and northern cryptic refugia in the grass snake Natrix natrix scutata (Pallas, 1771) (Squamata: Natricidae). Vertebrate Zoology, Volume 74, 565–576.