Wielstra Lab

In a paper in the Journal of Zoological Systematics and Evolutionary Research we explore the evolution of body form in crested newts. In general crested newts started out with large bodies with a short trunk and a wide head. Over time smaller bodies with a longer trunk and narrower had were added to the crested newt repertoire. Ecology likely played an important role in the radiation of body shapes in crested newts.

Reference: Vukov, T.D., Sotiropoulos, K., Wielstra, B., Džukić, G., Kalezić, M.L. (2011). The evolution of the adult body form of the crested newt (Triturus cristatus superspecies, Caudata, Salamandridae). Journal of Zoological Systematics and Evolutionary Research 49(4): 324-334.

Within the crested newt assemblage, known as the Triturus cristatus superspecies, T. karelinii has been severely understudied. Limited data suggests there might me more than one species involved and the systematic position within the crested newt superspecies is unclear. Furthermore, T. karelinii occurs in a region that is understudied from a biogeographical point of view: the Near East. Time to take a closer look!

This ‘geophylogeny’ shows a mitochondrial DNA phylogeography for Triturus karelinii plotted on a map. Note that there are three distinct clades, with their approximate range in different shades of blue.

In a paper published in Molecular Phylogenetics and Evolution, we present a range-wide mitochondrial DNA phylogeography. We show that T. karelinii is a monophyletic group that comprises three very distinct, geographically structured lineages. They are as different from one another as recognized crested newt species are. We also provide a historical biogeographical scenario to explain the origin of these lineages.

In the paper we explain the origin of the genetic variation in T. karelinii in the context of the paleogeology of Eurasia.

Reference: Wielstra, B., Espregueira Themudo, G., Güclü, Ö., Olgun, K., Poyarkov, N.A., Arntzen, J.W. (2010). Cryptic crested newt diversity at the Eurasian transition: the mitochondrial DNA phylogeography of Near Eastern Triturus newts. Molecular Phylogenetics and Evolution 56(3): 888-896.

Male crested newt of the T. karelinii-group (now called T. ivanbureschi). Picture by Michael Fahrbach.

The Triturus karelinii-group of crested newts has sometimes been considered to comprise two species, ‘T. karelinii proper’ in the east and ‘T. arntzeni’ in the west. Three hypotheses on the position of the boundary between the two have been suggested 1) somewhere in Thrace, 2) aligning with the sea strait system separating Europe and Asia, or 3) somewhere in western Anatolia. In a paper published in Amphibia-Reptilia we analysed allozyme data from Europe and north-western Turkey. We identified an eastern and a western group, in line with a two species treatment. These two groups show genetic admixture in western Anatolia, in line with hypothesis 3. However, the transition between the species is messy and unfortunately the eastern group is undersampled. Furthermore, two deeply divergent mitochondrial DNA clades suggest the transition between the two groups should be positioned further to the east. More questions than answers! Obviously, a more detailed survey on the crested newts of the Triturus karelinii-group is required.

Reference: Arntzen, J.W., Wielstra, B. (2010). Where to draw the line? A nuclear genetic perspective on proposed range boundaries of the crested newts Triturus karelinii and T. arntzeni. Amphibia-Reptilia 31(3): 311-322.

As the crested newts radiated in a short temporal interval, a relatively long time ago, it has proven extremely difficult to resolve their phylogenetic relationships. This might mean they truly did split simultaneously, or the amount of data studies may not have been sufficient. In a paper in Molecular Phylogenetics and Evolution we take another attempt to resolve the crested newt phylogeny. This time around we use sequence data for several nuclear and mitochondrial genes. I don’t think it actually got us much closer to a resolved phylogeny!

Reference: Esprequeira Themudo, G., Wielstra, B., Arntzen, J.W. (2009). Multiple nuclear and mitochondrial genes resolve the branching order of a rapid radiation of crested newts (Triturus, Salamandridae). Molecular Phylogenetics and Evolution 52(2): 321-328.

The genus Triturus comprises the marbled newts (such as T. pygmaeus on the left) and the crested newts (such as T. karelinii on the right). Pictures by Michael Fahrbach.

Despite the genus Triturus (in my humble opinion) being a model system in evolutionary research , the phylogenetic relationships among the different crested newt species have never been resolved. In a paper published in Contributions to Zoology, we consulted allozyme and mitochondrial DNA data to try and rectify this situation. However, despite the large amount of data, we did not manage to improve on the situation. The fuzziness of crested newt relationships might well reflect an actual simultaneous split. We compare time estimates of the crested newt radiation for the allozyme and mitochondrial DNA dataset. We conclude that only the latter can be brought in line with potential geological drivers and provide a biogeographical scenario. This paper was a good opportunity to split the distinct T. macedonicus from T. carnifex, we thought.

Reference: Arntzen, J.W., Esprequeira Themudo, G., Wielstra, B. (2007). The phylogeny of crested newts (Triturus cristatus superspecies): nuclear and mitochondrial genetic characters suggest a hard polytomy, in line with the paleogeography of the centre of origin. Contributions to Zoology 76(4): 261-278.