A multimarker phylogeography of crested newts (Triturus cristatus superspecies) reveals cryptic species

Abstract

The crested newt Triturus cristatus superspecies is composed of five recognized species. One of these, T. karelinii sensu lato, comprises three geographically structured mitochondrial DNA lineages: 'eastern', 'central' and 'western T. karelinii'. Genetic divergence among these lineages is comparable to that of recognized crested newt species, but morphologically they are indistinguishable. Here, we conduct a multimarker phylogeographical survey to explore the evolutionary independence of these mitochondrial DNA lineages and we include representatives of the other species to guide our interpretation of the results. All markers show distinct patterns when analyzed singly (as a phylogeny or haplotype network) and none of them sort haplotypes fully in line with species or mitochondrial DNA lineage. A multilocus approach (BAPS and *BEAST) on the other hand shows that not only the recognized species, but also the three mitochondrial DNA lineages represent discrete nuclear DNA gene pools. A mismatch is found in the northwest of Asiatic Turkey, where several populations identified as 'central T. karelinii' based on nuclear DNA possesses 'western T. karelinii' mitochondrial DNA. We invoke asymmetric mitochondrial DNA introgression to explain this pattern and support this with a historical biogeographical scenario. The three spatial groups in T. karelinii sensu lato should be regarded as distinct species.

Kicking Triturus arntzeni when it’s down: large-scale nuclear genetic data confirm that newts from the type locality are genetically admixed

“…The first hint of T. ivanbureschi representing a distinct species came from deep genetic divergence of mitochondrial DNA (Wielstra & Arntzen, 2011;Wielstra et al, 2010). These lineages were subsequently found to differ in environmental space and were eventually confirmed to also represent discrete nuclear gene pools (Wielstra et al, 2013a).…”

“…Wielstra et al (2013c) failed to obtain genetic data for the type material of T. arntzeni, presumably because of DNA degradation. Nuclear data available for other individuals from Vrtovać concerned just three markers, which was insufficient for a detailed examination of the newts' genetic composition (Wielstra et al, 2013a). The distribution of Triturus newts in eastern Serbia is intricate, but so much is clear that four species -next to T. ivanbureschi and T. macedonicus also T. cristatus (Laurenti, 1768) and T. dobrogicus (Kiritzescu, 1903) -are in parapatry (Fig.…”

A revised taxonomy of crested newts in the <i>Triturus karelinii</i> group (Amphibia: Caudata: Salamandridae), with the description of a new species

“…Based on a detailed phylogeographical survey of three nuclear DNA markers, the presence of three genetically distinct nuclear gene pools within T. karelinii s. l. was confirmed (Wielstra et al, 2013a), that we refer to as an eastern, a central and a western T. karelinii s. l. nuclear gene pool. The distribution of these nuclear gene pools corresponds to the three mitochondrial DNA lineages, with the exception of northwestern Asiatic Turkey, where western T. karelinii s. l. mitochondrial DNA is observed in the central T. karelinii s. l. nuclear gene pool (Fig.…”

“…1). Wielstra et al (2013a) suggested that partial geographical replacement of the western nuclear gene pool by the central T. karelinii s. l. nuclear gene pool coincided with asymmetric introgression of mitochondrial DNA. For a full biogeographical scenario of T. karelinii s. l., see Wielstra et al (2013a); .…”

“…A T. karelinii s. l. 'species tree' (i.e. a phylogeny based on multiple gene trees with their own coalescent models) based on the three nuclear DNA markers does not correspond to the mitochondrial DNA topology (see Wielstra et al, 2013a for a detailed discussion on potential 'contamination' by interspecific gene flow). However, a preliminary Triturus species tree based on more nuclear DNA markers (Wielstra et al, in prep.…”