Increased genetic structuring of isolatedSalamandra salamandrapopulations (Caudata: Salamandridae) at the margins of the Carpathian Mountains

Is there a massive glacial-Holocene flora continuity in Central Europe?

The prevailing paradigm about the Quaternary ecological and evolutionary history of Central European ecosystems is that they were repeatedly impoverished by regional extinctions of most species during the glacial periods, followed by massive recolonizations from southern and eastern refugia during interglacial periods. Recent literature partially contradicts this view and provides evidence to re-evaluate this Postglacial Recolonization Hypothesis and develop an alternative one. We examined the long-term history of the flora of the Carpathian (Pannonian) Basin by synthesising recent advances in ecological, phylogeographical, palaeoecological and palaeoclimatological research, and analysing the cold tolerance of the native flora of a test area (Hungary, the central part of the Carpathian Basin). We found that (1) many species have likely occurred there continuously since before the Last Glacial Maximum (LGM); (2) most of the present-day native flora (1404 species, about 80%) can occur in climates as cold as or colder than the LGM (mean annual temperature ≤+3.5°C); and (3) grasslands and forests can be species-rich under an LGM-like cold climate. These arguments support an alternative hypothesis, which we call the Flora Continuity Hypothesis. It states that long-term continuity of much of the flora in the Carpathian Basin is more plausible than regional extinctions during the LGM followed by massive postglacial recolonizations. The long-term continuity of the region's flora may have fundamental implications not only for understanding local biogeography and ecology (e.g. the temporal scale of processes), but also for conservation strategies focusing on protecting ancient species-rich ecosystems and local gene pools.

Genomic analysis reveals complex population structure within the smooth newt, Lissotriton vulgaris, in Central Europe

Species with wide-range distributions usually display high genetic variation. This variation can be partly explained by historical lineages that were temporally isolated from each other and are back into secondary reproductive contact, and partly by local adaptations. The smooth newt (Lissotriton vulgaris) is one of the most widely distributed amphibians species across Eurasia and forms a species complex with a partially overlapping distribution and morphology. In the present study, we explored the population genomic structure of smooth newt lineages in the Carpathian Basin (CB) relying on single-nucleotide polymorphisms. Our dataset included new and previously published data to study the secondary contact zone between lineages in the CB and also tested for the barrier effect of rivers to gene flow between these lineages. We confirmed the presence of the South L. v. vulgaris Lineage distributed in Transdanubia and we provided new distribution records of L. v. ampelensis inhabiting the eastern territories of the CB. High genetic diversity of smooth newts was observed, especially in the North Hungarian Mountains and at the interfluves of the main rivers in the South with four distinct lineages of L. v. vulgaris and one lineage of L. v. ampelensis showing a low level of admixture with the spatially closest L. v. vulgaris lineage. Moreover, admixture detected at the interfluve of the main rivers (i.e. Danube and Tisza) suggested a secondary contact zone in the area. Finally, we found that the river Danube has a very weak effect on population divergence, while the river Tisza is a geographical barrier limiting gene flow between smooth newt lineages. As the range boundaries of L. v. vulgaris and L. v. ampelensis in the CB coincide with the river Tisza, our study underpins the influence of rivers in lineage diversification.

Larval development and habitat usage of stream-breeding Fire salamanders in an urban environment

Urbanisation adversely affects the abiotic and biotic characteristics of watercourses, including freshwater streams that support the development of stream-breeding salamanders. We conducted a study over four years on an isolated fire salamander population inhabiting a stream valley northwest of Budapest, Hungary. Our aim was to understand aspects of larval development and habitat usage within this population. The maximum number of larvae was observed in April and the first weeks of May. Due to drifting caused by heavy rainfall, there was a mean decrease of 63.3% in the number of larvae. The abundance of larval salamanders within 16 stream segments showed strong temporal and spatial variation, and there was a strong relationship between larval abundance and the % cover of fine gravel substrate. Some of the larvae could escape drift by entering pools with slower water flow and shelter. Larvae were predominantly solitary in smaller pools but occasionally aggregated in high numbers in some segments. The first larvae with yellow spots (indicative of metamorphosis) appeared in June, and by early September, all larvae were metamorphosing. Our results show that in this urbanised environment, larval development through to metamorphosis is occurring, but increasing urbanisation and alterations to stream flow threaten the persistence of the local population.

Mitochondrial DNA diversity of the alpine newt (Ichthyosaura alpestris) in the Carpathian Basin: evidence for multiple cryptic lineages associated with Pleistocene refugia

The phylogeography and molecular taxonomy of the Alpine newt, Ichthyosaura alpestris, has been intensively studied in the past. However, previous studies did not include a comprehensive sampling from the Carpathian Basin, possibly a key region in the evolution of the species. We used a 1251 bp long fragment of the mitochondrial genome to infer the species’ evolutionary history in central-eastern Europe by assigning isolated Carpathian Basin populations from 6 regions to previously defined mtDNA lineages. We also revised the morphology-based intraspecific taxonomy of the species in the light of new genetic data. Alpine newt populations from the Carpathian Basin represented two different mitochondrial lineages. The Mátra, Bükk and Zemplén Mts populations can be assigned to the Western lineage of the nominotypical subspecies. Bakony and Őrség populations showed high haplotype diversity and formed a separate clade within the Western lineage, suggesting that the Carpathian Basin might have provided cryptic refugia for Alpine newt populations in their cold-continental forest-steppe landscapes during the younger Pleistocene. Newts from Apuseni Mts were related to the Eastern lineage but formed a distinct clade within this lineage. Considering the morphological and genetic differentiation of the Bakony and Őrség populations, consistent with a long independent evolutionary history, we propose these populations be referred to as Ichthyosaura alpestris bakonyiensis (Dely, 1964). We provide a redescription of this poorly known subspecies.

Landscape resistance constrains hybridization across contact zones in a reproductively and morphologically polymorphic salamander

Explicitly accounting for phenotypic differentiation together with environmental heterogeneity is crucial to understand the evolutionary dynamics in hybrid zones. Species showing intra-specific variation in phenotypic traits that meet across environmentally heterogeneous regions constitute excellent natural settings to study the role of phenotypic differentiation and environmental factors in shaping the spatial extent and patterns of admixture in hybrid zones. We studied three environmentally distinct contact zones where morphologically and reproductively divergent subspecies of Salamandra salamandra co-occur: the pueriparous S. s. bernardezi that is mostly parapatric to its three larviparous subspecies neighbours. We used a landscape genetics framework to: (i) characterise the spatial location and extent of each contact zone; (ii) assess patterns of introgression and hybridization between subspecies pairs; and (iii) examine the role of environmental heterogeneity in the evolutionary dynamics of hybrid zones. We found high levels of introgression between parity modes, and between distinct phenotypes, thus demonstrating the evolution to pueriparity alone or morphological differentiation do not lead to reproductive isolation between these highly divergent S. salamandra morphotypes. However, we detected substantial variation in patterns of hybridization across contact zones, being lower in the contact zone located on a topographically complex area. We highlight the importance of accounting for spatial environmental heterogeneity when studying evolutionary dynamics of hybrid zones.