Search

[Display omitted] • Next-generation phylogeography with sequence capture of marbled newts. • Lack of introgression supports species status of Triturus marmoratus and T. pygmaeus. • Genetically distinct groups found in both species. • Shows Iberian Peninsula's role driving inter- and intraspecific differentiation. European marbled newts come in two species that have abutting ranges. The northern species, Triturus marmoratus , is found in France and the northern part of the Iberian Peninsula, whereas the southern species, T. pygmaeus , is found in the southwestern corner of the Iberian Peninsula. We study the intraspecific genetic differentiation of the group because morphological data show geographical variation and because the Iberian Peninsula is a recognized center of speciation and intraspecific genetic diversity for all kinds of organisms, amphibians included. We use target enrichment by sequence capture to generate c. 7 k nuclear DNA markers. We observe limited genetic exchange between the species, which confirms their distinctiveness. Both species show substantial genetic structuring that is only in part mirrored by morphological variation. Genetically differentiated groups are found in the south (T. marmoratus) and west (T. pygmaeus) of the species ranges. Our observations highlight the position of the Iberian Peninsula as a hotspot for genetic differentiation. [ABSTRACT FROM AUTHOR]

Secondary contact between closely related species can lead to the formation of hybrid zones, allowing for interspecific gene flow. Hybrid zone movement can take place if one of the species possesses a competitive advantage over the other, ultimately resulting in species replacement. Such hybrid zone displacement is predicted to leave a genomic footprint across the landscape in the form of asymmetric gene flow (or introgression) of selectively neutral alleles from the displaced to the advancing species. Hybrid zone movement has been suggested for marbled newts in the Iberian Peninsula, supported by asymmetric gene flow and a distribution relict (i.e., an enclave) of Triturus marmoratus in the range of T. pygmaeus. We developed a panel of nuclear and mitochondrial SNP markers to test for the presence of a T. marmoratus genomic footprint in the Lisbon peninsula, south of the enclave. We found no additional populations of T. marmoratus. Analysis with the software Structure showed no genetic traces of T. marmoratus in T. pygmaeus. A principal component analysis showed some variation within the local T. pygmaeus, but it is unclear if this represents introgression from T. marmoratus. The results may be explained by (a) species replacement without introgressive hybridization and (b) displacement with hybridization followed by the near‐complete erosion of the footprint by purifying selection. We predict that testing for a genomic footprint north of the reported enclave would confirm that species replacement in these marbled newts occurred with hybridization. [ABSTRACT FROM AUTHOR]

We report the occurrence of facultative paedomorphosis in the three species of newts (Pleurodeles waltl, Lissotriton boscai and Triturus pygmaeus) from dry and seasonal Mediterranean areas from southern Spain. These are the first records of paedomorphosis for P. waltl and L. boscai, and the second for T. pygmaeus. Other than the previous T. pygmaeus record, these are the first observations of paedomorphosis in the southern half of the Iberian Peninsula. Most of specimens demonstrating paedomorphosis live in artificially permanent aquatic environments. Nevertheless, a paedomorphic individual of L. boscai was found in a natural yearly temporary brook that held water during the previous two years. Paedomorphs are at low frequency in most cases. However, a single isolated population of P. waltl is probably composed entirely of paedomorphs. [ABSTRACT FROM AUTHOR]

Aim To identify the ecological factors associated with the range borders of two amphibian species, to investigate geographical variation in environmental parameters that determine species range limits, and to develop a testable hypothesis on the species’ biogeographical history. Location Portugal and Spain. Methods We documented the distribution of two species of marbled newt ( Triturus marmoratus and Triturus pygmaeus) from atlas data, survey data and six latitudinal transects. Countrywide ecogeographical models were constructed from presence-only data and a suite of 19 environmental parameters. Local ecogeographical models were constructed along the contact zone. Results Triturus marmoratus and T. pygmaeus share a parapatric range border from coastal Portugal to central Spain. Ecogeographical models performed better in descriptive mode (for the country where they were developed) than in predictive mode (when extrapolated for the neighbouring country). This suggests the existence of spatial variation for parameters that determine the species range borders. Local models showed good performance in Spain and western Portugal. Parameters dominating the models were climatic (precipitation, temperature and solar radiation), geographical (altitude) and geophysical (soil permeability). Enclaves in the distribution of T. marmoratus/ T. pygmaeus also corresponded with environmental parameters. Poor-fitting local models were found in central Portugal, where the mutual range border of the two species coincides with the River Tejo. Main conclusions The fit and predictive performance of the ecogeographical models suggest that equilibrium conditions have been reached over most of the contact zone. Parameter selection, field observations and natural history knowledge led us to identify, in terms of reproductive strategy, a stable species with regular, but low annual recruitment ( T. marmoratus) vs. an opportunistic species with fluctuating ‘all-or-nothing’ annual recruitment ( T. pygmaeus). Ecological parapatry derives from the use of permanent ponds for breeding in T. marmoratus vs. ephemeral ponds used by T. pygmaeus. Enclaves in the distribution show that, historically, T. pygmaeus has been displacing T. marmoratus. In central Portugal, where the model fit is poor, the advance of T. pygmaeus is currently impeded by the River Tejo. We predict that once this barrier has been crossed, the contact zone will move c. 40 km to the north. As T. marmoratus and T. pygmaeus are hybridizing species, we predict the occasional presence of T. marmoratus genes in areas that have changed occupancy. [ABSTRACT FROM AUTHOR]