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We mapped the distribution for the past 18 years (2004-2022) of five protected amphibian species across Bulgaria using a spatial resolution of 100 m2 in CORINE Land Cover 2018 (CLC). Since the altitudinal distribution and habitat preferences of these species in the country make them potentially vulnerable to agricultural activities, the primary aim was to establish what part of the known records of each species falls within agricultural lands. Results indicated that all five studied species inhabit CLC types falling within the general type "Agricultural areas" (CLC Level 1: 2), with four species predominantly occurring in such regions. In total, three species (Bombina bombina, Triturus cristatus and T. ivanbureschi) had more than 50% of their distribution records in agricultural areas. In another species, Triturus dobrogicus, the percentage was above 40%. The lowest number (under 36%) was for B. variegata. For T. dobrogicus, nearly 32% of all records were concentrated in the CLC Level 3 category "Non-irrigated arable lands". This data suggests that a large percentage of the populations of these protected species across Bulgaria are potentially exposed to agricultural practices such as pesticide use, or crop land aggregation and highlight the need for regional approach for species protection. [ABSTRACT FROM AUTHOR]

Current knowledge of the vertical distribution of Triturus macedonicus places the species at altitudes up to 2140 m. Herein, we report its presence in the alpine lake Gistova at 2360 m on Mt. Grammos, Greece, thus extending the highest altitudinal point for the species, as well as for the Triturus genus. This record showcases the adaptive capacity of the Macedonian newt, which allows it to occupy markedly different environments. More populations may exist at similar or even higher altitudes and their discovery could positively impact conservation efforts. [ABSTRACT FROM AUTHOR]

Abstract Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mitochondrial genetic markers. Morphologically identified hybrids are mostly of the F1 generation and mothered by T. cristatus. The sex ratio of the F1 hybrid class is reciprocally skewed, with a preponderance of females in T. cristatus‐mothered hybrids and males in T. marmoratus‐mothered hybrids. This amounts to the Haldane effect operating in one direction of the cross. Deeper generation hybrids are occasionally produced, possibly including F1 hybrid × backcross hybrid offspring. Interspecific gene flow is low, yet skewed toward T. cristatus. This asymmetry may be caused by hybrid zone movement, with the superseding species being predisposed to introgression. The persisting gene flow between deeply differentiated species supports the notion that full genetic isolation may be selected against. Conversely, published morphological data suggest that introgressive hybridization is detrimental, with digital malformations occurring more frequently in the area of sympatry. Finally, to assist field identification, both within the area of natural range overlap and concerning anthropogenic introductions elsewhere, we document the phenotypical variation of two generations of hybrids compared with both parental species. We suggest that fluctuating range boundaries, ecological segregation, cytonuclear incompatibilities and hybrid breakdown through Bateson–Dobzhansky–Muller incompatibilities all contribute to species integrity, despite incomplete isolation during secondary contact.

Introductions of non‐native species can pose serious threats to native populations and ecosystems. However, the impact of introduced species depends on intrinsic characteristics, local habitat conditions, and the interaction with native species. Case‐specific management strategies may therefore be required. Using phenotypic characters and molecular markers for species identification, we provide insights into an artificial hybrid zone between two closely related newt species, the native Triturus cristatus and the introduced T. carnifex, near Tübingen, south‐west Germany. Our analyses revealed a central Italian origin of the non‐native T. carnifex and suggested their sustained presence in the study area for at least six years, probably much longer. In some ponds, extensive hybridization with native T. cristatus was detected. However, we found no evidence for a displacement of the native species by its non‐native congener. The gradient from pure T. carnifex to pure T. cristatus currently extends over 7 km. A future expansion of the hybrid zone and swamping of a neighboring T. cristatus meta‐population appears unlikely under the local configuration of breeding ponds. We propose to monitor the hybrid zone using genetic markers for evaluating the direction and speed of gene flow, complemented by capture‐recapture studies to reveal trends in species‐specific population sizes. To protect the native T. cristatus, we recommend practitioners to maintain their habitats, for example, by preventing illegal release of gold fish, by counteracting early drying of the breeding ponds, and by regularly cutting back trees and shrubs along the shoreline. [ABSTRACT FROM AUTHOR]

Abstract Introductions of non‐native species can pose serious threats to native populations and ecosystems. However, the impact of introduced species depends on intrinsic characteristics, local habitat conditions, and the interaction with native species. Case‐specific management strategies may therefore be required. Using phenotypic characters and molecular markers for species identification, we provide insights into an artificial hybrid zone between two closely related newt species, the native Triturus cristatus and the introduced T. carnifex, near Tübingen, south‐west Germany. Our analyses revealed a central Italian origin of the non‐native T. carnifex and suggested their sustained presence in the study area for at least six years, probably much longer. In some ponds, extensive hybridization with native T. cristatus was detected. However, we found no evidence for a displacement of the native species by its non‐native congener. The gradient from pure T. carnifex to pure T. cristatus currently extends over 7 km. A future expansion of the hybrid zone and swamping of a neighboring T. cristatus meta‐population appears unlikely under the local configuration of breeding ponds. We propose to monitor the hybrid zone using genetic markers for evaluating the direction and speed of gene flow, complemented by capture‐recapture studies to reveal trends in species‐specific population sizes. To protect the native T. cristatus, we recommend practitioners to maintain their habitats, for example, by preventing illegal release of gold fish, by counteracting early drying of the breeding ponds, and by regularly cutting back trees and shrubs along the shoreline.

Abstract 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.

[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]

Different amphibians and amphibian larvae were already observed and described as part of the diet of the European pond turtle. Few studies report body parts from adult newts in the stomach content of Emys orbicularis (Linnaeus, 1758) or newts predated by the same pond turtle species. We observed remains of Triturus dobrogicus (Kiritzescu, 1903) and Trituris ivanbureschi Arntzen & Wielstra, 2013 eaten by E. orbicularis inside funnel traps, which strongly suggests, that newts are part of the diet, although not typical and often eaten food by this pond turtle.

Deeply diverged yet hybridizing species provide a system to investigate the final stages of the speciation process. We study a hybridizing pair of salamander species—the morphologically and genetically drastically different newts Triturus cristatus and T. marmoratus—with a panel of 32 nuclear and mitochondrial genetic markers. Morphologically identified hybrids are mostly of the F1 generation and mothered by T. cristatus. The sex ratio of the F1 hybrid class is reciprocally skewed, with a preponderance of females in T. cristatus‐mothered hybrids and males in T. marmoratus‐mothered hybrids. This amounts to the Haldane effect operating in one direction of the cross. Deeper generation hybrids are occasionally produced, possibly including F1 hybrid × backcross hybrid offspring. Interspecific gene flow is low, yet skewed toward T. cristatus. This asymmetry may be caused by hybrid zone movement, with the superseding species being predisposed to introgression. The persisting gene flow between deeply differentiated species supports the notion that full genetic isolation may be selected against. Conversely, published morphological data suggest that introgressive hybridization is detrimental, with digital malformations occurring more frequently in the area of sympatry. Finally, to assist field identification, both within the area of natural range overlap and concerning anthropogenic introductions elsewhere, we document the phenotypical variation of two generations of hybrids compared with both parental species. We suggest that fluctuating range boundaries, ecological segregation, cytonuclear incompatibilities and hybrid breakdown through Bateson–Dobzhansky–Muller incompatibilities all contribute to species integrity, despite incomplete isolation during secondary contact. [ABSTRACT FROM AUTHOR]

During three consecutive years, we compared the reproductive characteristics and oviposition dynamics of two crested newt species, Triturus ivanbureschi and T. macedonicus. These two well-defined species are of special interest because of complex interactions at their contact zone, which include hybridization, species replacement and asymmetric mitochondrial DNA introgression. In common garden experiments, females were introduced to conspecific males, to males of other species and to hybrid males. We monitored the total number and size of the deposited eggs, as well as the dynamics and duration of oviposition during three consecutive years. The number of deposited eggs of Triturus species was much higher than previously reported. Triturus macedonicus lay more eggs that were of larger size in comparison to T. ivanbureschi. Also, the onset of T. macedonicus oviposition was considerably delayed compared to T. ivanbureschi. These are fundamental data, important for understanding complex species interactions in their contact zones.

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]

A lightweight, collapsible funnel trap designed for crayfish was furnished with a smaller mesh and then used to study adult breeding populations of five species of newts in five ponds in France. Observations were made in spring, at the peak of breeding activity, over an 11-year period. Annual experiments involved on average 7.7 traps and 5.3 overnight sampling sessions at 2.0 day intervals. In 95 out of 171 experiments (56%) the probability for an individual to go undetected was <1%. A trend was observed for catchability to increase with body size (Lissotriton < Ichthyosaura < Triturus). The two Triturus species involved were frequently exhaustively sampled in a single overnight session. In spite of their smaller size, L. helveticus males were more readily captured than females, presumably reflecting breeding associated locomotor activity. The numbers captured decreased over time suggesting 'trap shyness' to operate. We noted some predation by diving beetles (family Dytiscidae) affecting L. helveticus males in particular. [ABSTRACT FROM AUTHOR]

Four, morphologically similar species of crested newts (genus Triturus) meet and hybridize in Serbia, making a complex system with several hybrid zones. The puzzling and rapidly changing taxonomic status of crested newts has been a major issue in getting hold of their distribution. We provide an overview of the current knowledge on Triturus taxonomy and compile available faunistic data into a distribution map, highlighting the species contact and hybrid zones. At the present state of faunistic and genetic research, the north-western, north-eastern, eastern and south-eastern parts of Serbia transpire as areas that are exceptionally important for the diversity of crested newts. [ABSTRACT FROM AUTHOR]

In vertebrates with complex, biphasic, life cycles, larvae have a distinct morphology and ecological preferences compared to metamorphosed juveniles and adults. In amphibians, abrupt and rapid metamorphic changes transform aquatic larvae to terrestrial juveniles. The main aim of this study is to test whether, relative to larval stages, metamorphosis (1) resets the pattern of variation between ontogenetic stages and species, (2) constrains intraspecific morphological variability, and (3) similar to the "hour‐glass" model reduces morphological disparity. We explore postembryonic ontogenetic trajectories of head shape (from hatching to completed metamorphosis) of two well‐defined, morphologically distinct Triturus newts species and their F1 hybrids. Variation in head shape is quantified and compared on two levels: dynamic (across ontogenetic stages) and static (at a particular stage). Our results show that the ontogenetic trajectories diverge early during development and continue to diverge throughout larval stages and metamorphosis. The high within‐group variance and the largest disparity level (between‐group variance) characterize the metamorphosed stage. Hence, our results indicate that metamorphosis does not canalize head shape variation generated during larval development and that metamorphosed phenotype is not more constrained relative to larval ones. Therefore, metamorphosis cannot be regarded as a developmental constraint, at least not for salamander head shape. [ABSTRACT FROM AUTHOR]

A population of Northern crested newts, Triturus cristatus, was studied for 19 consecutive years (1998-2016) using individual recognition allowing the quantification of population dynamics and survival rates. Starting with a relatively high estimated number of adults (251 ± 55) and a long stable phase (144 ± 25) the population dropped six-fold (39 ± 10) by the end of the study. The population failed to recruit in nine years including a reproduction failure over four consecutive years of the 19-year study period. The yearly adult survival ranged from 18 to 98% with no differences between the sexes. Likely related to relative favourable survival rates of individuals older than 4+ of age and adult longevity of more than 16 years the population persisted. More long-term studies are urgently needed to assess how population dynamics are subject to local environmental factors or demographic patterns of the population itself. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Triturus newts show a correlation between body build and aquatic lifestyle. • The phylogeny of this adaptive radiation is currently unresolved. • We obtain c. 6000 markers with target enrichment by sequence capture. • Distinct phylogenetic methods all support a single topology. • The species tree supports gradual evolution of more elongated and aquatic newts. Abstract Newts of the genus Triturus (marbled and crested newts) exhibit substantial variation in the number of trunk vertebrae (NTV) and a higher NTV corresponds to a longer annual aquatic period. Because the Triturus phylogeny has thwarted resolution to date, the evolutionary history of NTV, annual aquatic period, and their potential coevolution has remained unclear. To resolve the phylogeny of Triturus , we generated a c. 6000 transcriptome-derived marker data set using a custom target enrichment probe set, and conducted phylogenetic analyses using: (1) data concatenation with RAxML, (2) gene-tree summary with ASTRAL, and (3) species-tree estimation with SNAPP. All analyses produce the same, highly supported topology, despite cladogenesis having occurred over a short timeframe, resulting in short internal branch lengths. Our new phylogenetic hypothesis is consistent with the minimal number of inferred changes in NTV count necessary to explain the diversity in NTV observed today. Although a causal relationship between NTV, body form, and aquatic ecology has yet to be experimentally established, our phylogeny indicates that these features have evolved together, and suggest that they may underlie the adaptive radiation that characterizes Triturus. [ABSTRACT FROM AUTHOR]

Invasive species are one of the main causes of amphibian declines worldwide, often through direct predation. Even species or life stages that may not be prone to predation by invasive animals can be affected through alterations of their reproductive behaviour and/or performance. This aspect is less commonly investigated, and may be important for understanding the full impact of invasive species on local amphibian populations. We used laboratory experiments to measure effects of the invasive Eastern mosquitofish (Gambusia holbrooki) on gravid pygmy newts (Triturus pygmaeus) from southern Spain. Gravid newts altered their position in the water column by moving from the bottom of the aquaria to the surface when in the presence of free-swimming mosquitofish, presumably to reduce physical contact with them. Newts also detected and consumed less prey in presence of free mosquitofish. Newts exposed to caged or free-swimming mosquitofish laid fewer eggs than newts not exposed to the invasive species, suggesting that chemical or visual cues alone were sufficient to alter the behaviour of gravid newts. Our results suggest that mosquitofish can reduce the reproductive success of native pygmy newts in the wild, highlighting the need for management efforts to mitigate this impact. [ABSTRACT FROM AUTHOR]

Inspired both by the literature reports and our previous findings on the question if a seasonal cycle alone, consisting of temperature and photoperiod variations, might impact on or activate natural proliferative fluctuations or unmask a latent spontaneous proliferative power in adult brain of poikilothermal Anamnia (fresh water, earth-dwelling) and Amniota (terrestrial), consequently allowing for encephalic reparative and even regenerative potentialities, an investigation has been carried on in normal adult brain of Triturus carnifex caught in nature in spring, summer, autumn. Cells immunostained for PCNA, i.e. cycling cells, were found scattered ("matrix cells") in the olfactory territories, where they appeared scarce in spring, more frequent in summer, noticeable in autumn; also, immunostained cells were found clustered in "matrix areas", also named zonae germinativae dorsales and ventrales, in the telencephalic hemispheres: few clusters in spring, an intermediate condition in summer, frequent cell groups in autumn. These results reveal an increasing trend in proliferation from spring, through summer, to autumn. This scenario was appreciable in the forebrain, mainly in the olfactory and telencephalic districts, which is the typical site of stem cells. Signs of potential proliferative activity are well appreciable in the urodele Amphibians, which are the best provided among vertebrates with reparative and regenerative power and possess the richest endowment of dormant cells susceptible to be recruited to proliferation. [ABSTRACT FROM AUTHOR]

Dispersal is one of the main processes that determine community structure. Individuals make dispersal decisions according to environmental and/or social cues that reflect the fitness prospects in a given patch. The presence and abundance of heterospecifics within the same ecological guild, and/or their breeding success, may act as public information that influences movement decisions. To date, most studies investigating the role of heterospecific attraction have focused on habitat choice, using both experimental and correlational approaches. The present study is the first to examine how long-term variation in heterospecific density in breeding patches may affect dispersal patterns in spatially structured populations. We investigate how the dispersal decisions of the great crested newt (Triturus cristatus) are related to the variable density of two other newt species, the alpine newt (Ichthyosaura alpestris) and the palmate newt (Lissotriton helveticus). To examine this issue, we used capture-recapture data collected in an experimental pond network over a 20-year period. The results revealed that the great crested newt’s dispersal is context dependent and is affected by variation in heterospecific density: individuals were less likely to emigrate from ponds with high heterospecific density and were more likely to immigrate to ponds with high heterospecific density. These findings suggest that individuals adjust their dispersal decisions at least partly based on public information provided by heterospecifics. This mechanism may play a critical role in the dynamics of spatially structured populations and community functioning. [ABSTRACT FROM AUTHOR]

Intraspecific trait variation in generalist animals is widespread in nature, yet its effects on community ecology are not well understood. Newts are considered opportunistic feeders that may co-occur in different syntopic conditions and represent an excellent model for studying the role of individual feeding specialization in shaping the population dietary strategy. Here, we investigated the diet of three newt species from central Italy occurring in artificial habitats in different coexistence conditions to test the predictions of the niche width (NW) variation hypotheses. Population NW did not vary among species and between presence and absence of coexisting species. An overall positive relationship between individual specialization and population NW was observed. However, this pattern was disrupted by the condition of syntopy with newt populations showing an individual NW variation invariant with population NW in presence of coexisting species, whereas it was larger in populations occurring alone. The observed pattern of newt behavior was not consistent with any of the proposed scenarios. We found a consistent pattern with the degree of individual specialization being (1) size-dependent (specialized individuals increasing within larger sized species) and (2) assemblage-complexity-dependent (specialized individuals increasing in syntopic populations in comparison to singly populations).

In amphibians, morphological differentiation and disparity at the larval and post-metamorphic ontogenetic stages can diverge, owing to various contrasting environments and different selective pressures. In the monophyletic clade of nine Triturus newt species, five different morphotypes can be recognized, but information on larval morphology is limited. Here we explore divergence of larval morphology in Triturus ivanbureschi, T. macedonicus, and their F1 hybrids. These two genetically and morphologically distinct crested newt species hybridize in nature and form a relatively wide hybrid zone in the central part of the Balkan Peninsula. Using a geometric morphometric approach and multivariate statistics, we evaluated differences of tail size and shape, colouration pattern, and the presence of a tail filament at the mid-larval stage in larvae reared under controlled laboratory conditions. We chose the tail as the main propulsive organ crucial for locomotion, feeding, and escaping predators. We found that Triturus ivanbureschi and T. macedonicus larvae differ in tail shape, but not in tail size. Two groups of F1 hybrid larvae (obtained from reciprocal crossing) were similar to each other, but differed from the parental species in size and shape of the tail, colouration pattern, and the presence of a tail filament. Our results indicate that, like adults, larvae diverge morphologically and hybrid larvae do not exhibit intermediate morphology of the parental species. [ABSTRACT FROM AUTHOR]

In the spring of the years 2016 and 2017 we identified seven new distribution localities of the Danube crested newt, Triturus dobrogicus, in southern Romania. All seven localities are situated in the Danube floodplain or in its close proximity, at an altitude below 100 m. Thus, the new distribution records are situated inside the species distribution range. Nevertheless, the locality from Olt County represent, compared with the previous data from the literature, the first mention of T. dobrogicus in the region. This underlines the precarity of the information concerning the distribution of T. dobrogicus in southern Romania, even nowadays. [ABSTRACT FROM AUTHOR]

Understanding how species have replaced each other in the past is important to predicting future species turnover. While past species replacement is difficult to detect after the fact, the process may be inferred from present-day distribution patterns. Species with abutting ranges sometimes show a characteristic distribution pattern, where a section of one species range is enveloped by that of the other. Such an enclave could indicate past species replacement: when a species is partly supplanted by a competitor, but a population endures locally while the invading species moves around and past it, an enclave forms. If the two species hybridize and backcross, the receding species is predicted to leave genetic traces within the expanding one under a scenario of species replacement. By screening dozens of genes in hybridizing crested newts, we uncover genetic remnants of the ancestral species, now inhabiting an enclave, in the range of the surrounding invading species. This independent genetic evidence supports the past distribution dynamics we predicted from the enclave. We suggest that enclaves provide a valuable tool in understanding historical species replacement, which is important because a major conservation concern arising from anthropogenic climate change is increased species replacement in the future. [ABSTRACT FROM AUTHOR]

Salamanders have evolved a wide variety of antipredator mechanisms and behavior patterns, including toxins and noxious or adhesive skin secretions. The high bonding strength of the natural bioadhesives makes these substances interesting for biomimetic research and applications in industrial and medical sectors. Secretions of toxic species may help to understand the direct effect of harmful substances on the cellular level. In the present study, the biocompatibility of adhesive secretions from four salamander species ( Plethodon shermani , Plethodon glutinosus , Ambystoma maculatum , Ambystoma opacum ) were analyzed using the MTT assay in cell culture and evaluated against toxic secretions of Pleurodeles waltl , Triturus carnifex , Pseudotriton ruber , Tylototriton verrucosus , and Salamandra salamandra . Their effect on cells was tested in direct contact (direct culture) or under the influence of the extract (indirect exposure) in accordance with the protocol of the international standard norm ISO 10993-5. Human dermal fibroblasts (NHDF), umbilical vein endothelial cells (HUVEC), and articular chondrocytes (HAC), as well as the cell lines C2C12 and L929 were used in both culture types. While the adhesive secretions from Plethodon shermani are cytocompatible and those of Ambystoma opacum are even advantageous, those of Plethodon glutinosus and Ambystoma maculatum appear to be cytotoxic to NDHF and HUVEC. Toxic secretions from Salamandra salamandra exhibited harmful effects on all cell types. Pseudotriton ruber and Triturus carnifex secretions affected certain cell types marginally; those from Pleurodeles waltl and Tylototriton verrucosus were generally well tolerated. The study shows for the first time the effect of salamander secretions on the viability of different cell types in culture. Two adhesive secretions appeared to be cell compatible and are therefore promising candidates for future investigations in the field of medical bioadhesives. Among the toxic secretions tested, only two of the five had a harmful effect on cells, indicating different cell toxicity mechanisms. [ABSTRACT FROM AUTHOR]

When related species meet upon postglacial range expansion, hybrid zones are frequently formed. Theory predicts that such zones may move over the landscape until equilibrium conditions are reached. One hybrid zone observed to be moving in historical times (1950-1979) is that of the pond-breeding salamanders Triturus cristatus and Triturus marmoratus in western France. We identified the ecological correlates of the species hybrid zone as elevation, forestation, and hedgerows favoring the more terrestrial T. marmoratus and pond density favoring the more aquatic T. cristatus. The past movement of the zone of ca. 30 km over three decades has probably been driven by the drastic postwar reduction of the 'bocage' hedgerow landscape, favoring T. cristatus over T. marmoratus. No further hybrid zone movement was observed from 1979 to the present. To explain the changing dynamics of the hybrid zone, we propose that it stalled, either because an equilibrium was found at an altitude of ca. 140 m a.s.l. or due to pond loss and decreased population densities. While we cannot rule out the former explanation, we found support for the latter. Under agricultural intensification, ponds in the study area are lost at an unprecedented rate of 5.5% per year, so that remaining Triturus populations are increasingly isolated, hampering dispersal and further hybrid zone movement. [ABSTRACT FROM AUTHOR]

Ectotherms are particularly sensitive to global warming due to their limited capacity to thermoregulate, which can impact their performance and fitness. From a physiological standpoint, higher temperatures often enhance biological processes that can induce the production of reactive oxygen species and result in a state of cellular oxidative stress. Temperature alters interspecific interactions, including species hybridization. Hybridization under different thermal conditions could amplify parental (genetic) incompatibilities, thus affecting a hybrid's development and distribution. Understanding the impact of global warming on the physiology of hybrids and particularly their oxidative status could help in predicting future scenarios in ecosystems and in hybrids. In the present study, we investigated the effect of water temperature on the development, growth and oxidative stress of two crested newt species and their reciprocal hybrids. Larvae of Triturus macedonicus and T. ivanbureschi, and their T. macedonicus -mothered and T. ivanbureschi -mothered hybrids were exposed for 30 days to temperatures of 19°C and 24°C. Under the higher temperature, the hybrids experienced increases in both growth and developmental rates, while parental species exhibited accelerated growth (T. macedonicus) or development (T. ivanbureschi). Warm conditions also had different effects on the oxidative status of hybrid and parental species. Parental species had enhanced antioxidant responses (catalase, glutathione peroxidase, glutathione S-transferase and SH groups), which allowed them to alleviate temperature-induced stress (revealed by the absence of oxidative damage). However, warming induced an antioxidant response in the hybrids, including oxidative damage in the form of lipid peroxidation. These findings point to a greater disruption of redox regulation and metabolic machinery in hybrid newts, which can be interpreted as the cost of hybridization that is likely linked to parental incompatibilities expressed under a higher temperature. Our study aims to improve mechanistic understanding of the resilience and distribution of hybrid species that cope with climate-driven changes. [Display omitted] • Global warming can alter physiology and distribution of ectothermic species. • We study effect of temperature on oxidative stress of newt species and their hybrids. • Hybrids increased both growth and developmental rates under higher temperature. • Warm conditions had different effects on the oxidative status of hybrids and parents. • Greater oxidative damage in hybrid newts may be understood as a cost of hybridization. [ABSTRACT FROM AUTHOR]

Detection dogs are increasingly used to locate cryptic wildlife species, but their use for amphibians is still rather underexplored. In the present paper we focus on the great crested newt (Triturus cristatus), a European species which is experiencing high conservation concerns across its range, and assess the ability of a trained detection dog to locate individuals during their terrestrial phase. More specifically, we used a series of experiments to document whether a range of distances between target newts and the detection dog (odour channelled through pipes 68 mm in diameter) affects the localisation, and to assess the ability and efficiency of target newt detection in simulated subterranean refugia through 200 mm of two common soil types (clay and sandy soil, both with and without air vents to mimic mammal burrows, a common refuge used by T. cristatus). The detection dog accurately located all individual T. cristatus across the entire range of tested distances (0.25 m- 2.0 m). The substrate trials revealed that the detection dog could locate individuals also through soil. Contrary to existing studies with detection dogs in human forensic contexts, however, detection was generally slower for T. cristatus under sandy soil compared to clay soil, particularly when a vent was absent. Our study provides a general baseline for the use of detection dogs in locating T. cristatus and similar amphibian species during their terrestrial phase., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Glover et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Genetic admixture between endangered native and non-native invasive species poses a complex conservation problem. Decision makers often need to quickly screen large numbers of individuals and distinguish natives from morphologically similar invading species and their genetically admixed offspring. We describe a protocol using the fast and economical Kompetitive Allele Specific PCR (KASP) technology for genotyping on a large scale. We apply this protocol to a case study of hybridization between a native and an invasive crested newt species. Using previously published data, we designed a panel of ten nuclear and one mitochondrial diagnostic SNP markers. We observed only minor differences between KASP and next-generation sequencing data previously produced with the Ion Torrent platform. We briefly discuss practical considerations for tackling the insidious conservation problem of genetic admixture between native and invasive species. The KASP genotyping protocol facilitates policy decision making for the crested newt case and is generally applicable to invasive hybridization with endangered taxa. [ABSTRACT FROM AUTHOR]