Invasive species are considered one of the main drivers of the sixth mass extinction. Conservation solutions depend on whether a species is also indigenous to the country it invades (i.e., beyond... Show moreInvasive species are considered one of the main drivers of the sixth mass extinction. Conservation solutions depend on whether a species is also indigenous to the country it invades (i.e., beyond its native range). In the case of invasive cryptic species, genetic tools are required to establish their identity. We illustrate these issues with the human-mediated colonization of the Dutch coastal dunes by Hyla tree frogs. Although previously assumed to concern the indigenous common tree frog H. arborea, European tree frogs comprise a complex of allopatric cryptic species, meaning the taxonomic identity of introduced Dutch populations warrants investigation. We sequence mtDNA for 173 individuals from native and introduced populations across the Netherlands and compare our dataset with hundreds of Hyla haplotypes previously barcoded in the Western Palearctic. Two of the dune populations carry an mtDNA haplotype of the native species H. arborea that occurs naturally elsewhere in the Netherlands. In contrast, mtDNA assigned to the eastern tree frog H. orientalis was detected in all three other dune populations. In one of these populations mtDNA of the Italian tree frog H. intermedia was also found. Not one, but three species of tree frogs have thus been introduced to the Dutch coastal dunes, only one of them being native to the Netherlands. This situation causes a conservation conundrum as some introduced populations are lawfully protected but could pose a threat to local biodiversity. Regarding the 'true' exotic tree frog species, all conservation options should be considered. Show less
Vliegenthart, C.; Vrede, M. van de; Boer, I. den; Gilbert, M.J.; Lemmers, P.; France, J.M.; ... ; Wielstra, B.M. 2023
For most if not all European herpetofauna, range-wide mtDNA phylogeographies have been published. This facilitates establishing the provenance of introduced populations. However, precision is... Show moreFor most if not all European herpetofauna, range-wide mtDNA phylogeographies have been published. This facilitates establishing the provenance of introduced populations. However, precision is contingent on the spatial genetic structure across the range of the taxon under study and, in particular, from where within that range the introduction was sourced. In the Netherlands, the common midwife toad, Alytes obstetricans, only naturally occurs in the extreme southeast and is on the decline there. Yet, introduced populations thrive elsewhere in the country. We use mtDNA analysis to try to determine the origin of two introduced populations along the Dutch coast, in the city of The Hague and the dune area Meijendel. We compiled a database of hundreds of individuals from throughout the distribution range and added over 130 individuals from both native and introduced populations from the Netherlands, Belgium and Germany. The mtDNA haplotypes found in the introduced populations are associated with postglacial expansion. The main haplotype predominates in the natural range in the Netherlands, but also occurs much more widely across western Europe, north of the Pyrenees. A closely related haplotype, newly identified from The Hague, was not found in the native Netherlands range, suggesting an origin from abroad. The combination of low phylogeographic resolution and low sampling density in the postglacially colonized part of the range hampers our ability to determine the provenance of the introduced A. obstetricans populations. Show less
Brouwer, J. de; Helder, B.; France, J.M.; Visser, M.C. de; Struijk, R.P.J.H.; Wielstra, B.M. 2023
Isolated distribution patches may represent local remnants of a formerly wider range or could have originated by human-mediated expansion beyond the natural range. Distinguishing between these two... Show moreIsolated distribution patches may represent local remnants of a formerly wider range or could have originated by human-mediated expansion beyond the natural range. Distinguishing between these two scenarios is not always straightforward. Northern crested newts (Triturus cristatus) in the Dutch coastal dunes are disconnected from the main species range by over 40 kilometres and whether they have been present historically is unclear. We genotyped crested newts from throughout the Netherlands for an mtDNA marker to determine the provenance of the coastal dune population. Because a closely related species, the Italian crested newt (T. carnifex), has an introduction history in the Netherlands, we also screened eight nuclear DNA SNP markers diagnostic for T. cristatus vs. T. carnifex. The crested newts from the coastal dunes carry a single T. cristatus mtDNA haplotype that naturally occurs in the south, but not the east, of the Netherlands. Therefore, we cannot distinguish if the population represents a natural distribution relict or is derived from an introduction. We find no evidence of genetic admixture with T. carnifex in the coastal dunes, but such admixture is apparent at another Dutch locality (far removed from a previously known genetically admixed population). Our study illustrates how difficult it can be to determine the origin of isolated populations. Show less
Species that are threatened in their native range may actually prosper as introduced populations. To investigate how such introduced populations were established involves determining from where... Show moreSpecies that are threatened in their native range may actually prosper as introduced populations. To investigate how such introduced populations were established involves determining from where within the natural range the founder individuals originated. This can be accomplished through mtDNA barcoding. The common spadefoot toad (Pelobates fuscus) naturally occurs in the south and east of the Netherlands and has shown a rapid decline. Yet, a flourishing introduced population was recently discovered in the coastal dunes in the west of the country. We use mtDNA barcoding to determine the provenance of the introduced population. We sampled both native and introduced populations from the Netherlands and compared our sequences to haplotypes from across the entire distribution range. The mtDNA haplotypes found in the introduced population are distinct from those naturally occurring in the Netherlands and point towards an origin in the Pannonian Basin, on the boundary between Central and Southeastern Europe. Paradoxically, the thriving P. fuscus population in the Dutch coastal dunes should be considered a conservation risk to local biodiversity, even though within the native range in the Netherlands the species is severely threatened. Our study illustrates the complicated conservation questions associated with species that are both native and invasive. Show less
The ‘smooth newt’, the taxon traditionally referred to as Lissotriton vulgaris, consists of multiple morphologically distinct taxa. Given the uncertainty concerning the validity and rank of these... Show moreThe ‘smooth newt’, the taxon traditionally referred to as Lissotriton vulgaris, consists of multiple morphologically distinct taxa. Given the uncertainty concerning the validity and rank of these taxa, L. vulgaris sensu lato has often been treated as a single, polytypic species. A recent study, driven by genetic data, proposed to recognize five species, L. graecus, L. kosswigi, L. lantzi, L. schmidtleri and a more restricted L. vulgaris. The Carpathian newt L. montandoni was confirmed to be a closely related sister species. We propose to refer to this collective of six Lissotriton species as the smooth newt or Lissotriton vulgaris species complex. Guided by comprehensive genomic data from throughout the range of the smooth newt species complex we 1) delineate the distribution ranges, 2) provide a distribution database, and 3) produce distribution maps according to the format of the New Atlas of Amphibians and Reptiles of Europe, for the six constituent species. This allows us to 4) highlight regions where more research is needed to determine the position of contact zones. Show less
The Danube crested newt Triturus dobrogicus has been proposed to comprise two subspecies: T. d. dobrogicus and T. d. macrosoma. Uncertainty exists in the literature over their distribution and... Show moreThe Danube crested newt Triturus dobrogicus has been proposed to comprise two subspecies: T. d. dobrogicus and T. d. macrosoma. Uncertainty exists in the literature over their distribution and diagnosability. We conduct a multilocus phylogeographical survey and review published data to determine whether a two taxon treatment is warranted. Newly produced and published nuclear DNA data suggest intraspecific variation in the Pannonian Plain part of the range, but with extensive genetic admixture, whereas mitochondrial DNA data shows a lack of geographical structuring in T. dobrogicus altogether. None of the studied morphological characters suggest the presence of two geographical groups in T. dobrogicus unequivocally. Although Danube Delta newts do have relatively short bodies compared to the remainder of the range (the Pannonian and Lower Danube Plains and the Dnepr Delta), we argue that this finding can be explained by phenotypic plasticity - particularly in light of the incongruent evolutionary scenario suggested by genetic data. We conclude that the total body of evidence does not support the two subspecies hypothesis and recommend that T. dobrogicus is treated as a monotypic species. Show less
In the recently published New Atlas of Amphibians and Reptiles of Europe (Sillero et al., 2014a), the distribution of the newt genus Triturus was not resolved at the level of the species. The main... Show moreIn the recently published New Atlas of Amphibians and Reptiles of Europe (Sillero et al., 2014a), the distribution of the newt genus Triturus was not resolved at the level of the species. The main reason for this was the lack of high quality distribution data from in and around the parapatric contact zones between species, where interspecific hybridization occurs. We are working extensively on Triturus and the (particularly genetic) data we have accumulated allow us to map the individual Triturus species at the appropriate scale. We here provide a database composed of distribution data for the individual species, at generally high resolution, particularly from in and around contact zones. Based on this database we produce maps at the 50 x 50 km UTM grid resolution as used in the new atlas and highlight those grid cells in which more than one Triturus species occurs. Show less
The group of crested newts distributed from the southern Balkans to the southern shore of the Caspian Sea, Triturus karelinii sensu lato, comprises two species, T. karelinii in the east and T.... Show moreThe group of crested newts distributed from the southern Balkans to the southern shore of the Caspian Sea, Triturus karelinii sensu lato, comprises two species, T. karelinii in the east and T. arntzeni in the west. Three hypotheses have been forwarded defining the range of T. arntzeni, namely from northern Serbia eastwards i) in to Thrace, ii) up to the Aegean-Black Sea waterway including the Bosporus, or iii) into western Anatolia. We study 130 newts from 22 populations across this area with a panel of 40 enzyme nuclear genes. A combined analysis with the computer programs Structure and NewHybrids reveals the existence of two groups with admixture at two localities. The 'western group' comprises all European populations and a population at the southern shore of the Sea of Marmara in Asiatic Turkey, whereas the 'eastern group' is found at the Sakarya river valley in northern Anatolia, Asiatic Turkey. The admixed populations are also located in northern Anatolia. An analysis with the computer program BAPS resolves six genetic clusters, of which three represent the 'western group' and the other three coincide with the 'eastern group' and the two admixed populations. These analyses indicate that the species transition from T. arntzeni to T. karelinii is not in Thrace but in northern Anatolia. The presence of 'western' T. arntzeni to the east of 'eastern' T. karelinii indicates that the species' contact zone has a convoluted shape. Moreover, the spatial distribution of diagnostic allozymes only roughly coincides with that of two deeply divergent mitochondrial DNA haplotypes. A more detailed survey on the crested newt distribution in Anatolia is required to elucidate the picture further. Show less
