A male pygmy marbled newt (the bold one on the left) and a male marbled newt (looking rather submissive). Pictures by Michael Fahrbach.

The hybrid zone between the marbled newt (Triturus marmoratus) and the pygmy marbled newt (T. pygmaeus) is probably moving northwards. This movement was initially predicted based on enclaves of the northern species (T. marmoratus), positioned well inside the range of the southern species (T. pygmaeus). In species with limited dispersal capabilities, such as newts, enclaves most likely represent a species holding on locally, while a competitor is gradually overtaking it. If the two species involved also hybridize, then enclaves are a good marker of hybrid zone movement.

The hybrid zone between the pygmy marbled newt (light) and marbled newt (dark) is hypothesized to move northwards, based on marbled newt distribution relics left in the wake of the hybrid zone.

In a paper published in the Journal of Zoological Systematics and Evolutionary Research we use the Triturus Ion Torrent protocol, to see if we can confirm movement of the marbled newt hybrid zone, by testing for a genomic footprint of hybrid zone movement. Our sampling is rather limited, but south of the hybrid zone, in T. pygmaeus territory, we find the predicted genetic traces of the displaced T. marmoratus.

Reference: Arntzen, J.W., López-Delgado, J., van Riemsdijk, I., Wielstra, B. (2021). A genomic footprint of a moving hybrid zone in marbled newts, Portugal. Journal of Zoological Systematics and Evolutionary Research 59(2): 459-465.