The crested newt traditionally referred to as ‘Triturus karelinii’ comprises three distinct mitochondrial DNA clades. These clades are found in the east, the centre and the west of the range. The difference between mitochondrial DNA clades is comparable to the difference between the mitochondrial DNA of recognized crested newt species. We wanted to see if the three mitochondrial DNA clades might in fact represent different species.

This plot shows individuals (thin bars) within populations (thick bars) roughly ordered from west to east. Based on their genotype, individuals are allocated (0-100%) to three geographical genetic groups (represented by different colors).

In a paper published in Molecular Phylogenetics and Evolution we show that, based on three nuclear genes, there are three discrete geographical groups, in line with the three species hypothesis. We suggest that these three groups should be considered distinct species, but as it is as yet unclear if they can be distinguished based on morphology, we refer to them as ‘cryptic species’ for now.

Here you see the three cryptic species that make up the T. karelinii-group of crested newts. An intriguing finding is that asymmetric DNA introgression from the western group into the central group (the red-green hatched area). We suggest that this pattern can be explained by the central group having expanded its range at the expense of the western group, while the two hybridized in the process. An interesting hypothesis to test in a future study!

Reference: Wielstra, B., Baird, A.B., Arntzen, J.W. (2013). A multimarker phylogeography of crested newts (Triturus cristatus superspecies) reveals cryptic species. Molecular Phylogenetics and Evolution 67(1): 167-175.