Abstract The olm, Proteus anguinus , is one of the most iconic vertebrates of Europe. Since its scientific description in 1768, its extreme adaptations to subterranean life in the enigmatic underground waters of the Dinaric Karst have fascinated scholars and naturalists worldwide for more than two centuries. Yet, the evolution and taxonomic diversity of its populations remained largely unresolved, as complex patterns of phenotypic differentiation and molecular variation collide with an intricate nomenclatural history. In this work, we review recent biogeographic advances, notably based on range-wide phylogeographic analyses implementing genomic data, and combined with distributional data, species distribution modelling, red list assessment, morphological analyses and a critical species delimitation evaluation, recognize nine species in immediate danger of extinction. Based on an extensive nomenclatural search, we determined that six correspond to available names and three are newly described in this work. These species all exhibit highly restricted distributions within the Dinaric karst, collectively representing an exceptional example of subterranean microendemism among European vertebrates. Linking influential historical research with modern zoological methods, this revision provides an up-to-date science-based taxonomic framework for future studies of comparative evolution and ecology of Proteus , while establishing a sound basis for species-level conservation management of one of Europe’s most remarkable vertebrate diversifications.
The common spadefoot toad (Pelobates fuscus) is a declining amphibian whose movement patterns and terrestrial habitat use are not well known. The daily positions of 51 common spadefoot toads were monitored by telemetry at two sites along the Lower Rhine valley, France. Fluorescent pigments were used to monitor the nocturnal movements of 91 individuals in three populations in the same area. This study aimed to (i) characterise terrestrial movement patterns and estimate home ranges, and (ii) identify the preferred habitat types of this fossorial amphibian. The median home range size was 0.35 ha. We counted an average of 6.9 burrows per individual and individuals spent an average of 2.7 days in a burrow. The average distance travelled in 24 h was 12.5 m with a maximum of 136.7 m. The average distance to the nearest breeding pond was 245.6 m, and this distance could be up to 777 m. The common spadefoot avoided shrubby areas, preferring forest litter (especially forest edges) and corn fields for its daily burrows. These results highlight the importance of protecting a wide range of habitats for this sedentary species with a predominantly terrestrial lifestyle.
Abstract Hynobius amjiensis is a nationally protected species of major conservation concern in China, and understanding its reproductive behaviour is essential for developing effective conservation measures. This study conducted observations on its breeding behaviour during the 2024-2025 breeding season, utilizing digital video recording to collect behavioural data. The results demonstrated that the average time for female H. amjiensis to complete egg mass deposition was 63 ± 33 s, while the duration of males holding onto the egg mass was 207 ± 90 s. The entire process from oviposition to fertilization (when the male releases the egg mass) took an average of 461 ± 182 seconds. The study revealed that H. amjiensis exhibits reproductive behaviour characteristic of the family Hynobiidae including: (1) males pursuing females and engaging in head contact and grasping during the courtship period; (2) a preference for specific substrates for egg mass attachment; (3) competition over egg masses in the form of “amplexus balls”; and (4) presence of behaviours associated with male parental care, not only in the primary male that fertilized the eggs but possibly among multiple males nearby. Additionally, the study identified specific behaviours distinct to this species: (1) females exhibited unique responsive behaviours during courtship by actively approaching males and sniffing their cloacal region, suggesting a possible special pheromone communication; (2) dominant males displayed clear spatially dependent attacking strategies against competitors. This research provides a detailed account of the reproductive behaviour of the H. amjiensis , contributing scientific evidence for its conservation, management, and practices such as artificial breeding.
Defining and delimiting species boundaries is a challenging task, even for specialists. After a species is described, subsequent taxonomic revisions may lump it with another taxon, split it into two or more species, or even reclassify it into a different taxon. These changes in species taxonomy can cause instability in the list of species considered valid over time, which can affect macroecological predictions and have consequences for conservation planning and biodiversity management. In this study, we use five macroecological variables and four factors associated with the taxonomic history of New World coralsnakes to investigate whether these variables can predict the likelihood of a species undergoing taxonomic revision, leading to changes in its taxonomy. Some of the authors, experts on the group, identified, drawing on their knowledge, which species have a higher likelihood of undergoing taxonomic change. Our findings indicate that the number of synonyms, body size, and the latitude of the centroid positively affect the probability of a species splitting in the future. The necessity for a species to undergo taxonomic revision increases with the number of subspecies, and the level of difficulty in delimiting a species increases with the number of synonyms. We demonstrated that most coralsnake species exhibit some degree of taxonomic uncertainty, with these species predominantly found in moist broadleaf forests. If macroecological and taxonomic variables can be used to predict the taxonomic uncertainty of other taxonomic groups, we could enhance our understanding of how taxonomic uncertainty affects our perception of macroecological patterns and conservation planning. Additionally, this approach could help identify which species need more taxonomic attention.
Abstract Predation risk is a major selective force shaping antipredator strategies, including aposematism. Although adult fire salamanders ( Salamandra salamandra ) are widely regarded as experiencing low predation pressure due to their conspicuous coloration and potent skin toxins, several vertebrates have been reported to consume them. The extent to which these species act as effective consumers of aposematic salamanders, however, remains poorly understood due to methodological constraints and the scarcity of direct observations. Here, we combined camera-trap monitoring with the experimental deployment of salamander carcasses to evaluate the roles of the European badger ( Meles meles ) and the wood mouse ( Apodemus sylvaticus ) as consumers of S. salamandra in a heterogeneous forest in northwestern Spain. Across two sampling periods (autumn 2024 and spring 2025), we recorded 440 independent events for A. sylvaticus (1090 total videos) and 36 for M. meles (83 total videos). Although badgers were frequently detected near their setts, none of the recorded events showed carcass manipulation or consumption. In contrast, wood mice interacted extensively with carcasses, with 37% of independent events involving biting or consumption and a significantly higher consumption rate in spring. These results identify A. sylvaticus as an important and previously underestimated consumer of aposematic salamanders, with seasonal variation likely driven by resource availability. Our findings highlight the value of experimental field approaches for quantifying consumption pressure on chemically defended amphibians and underscore the complexity of mammalian responses to aposematic defences.
Abstract Taxonomic identification of introduced amphibian populations – a crucial first step for conservation management – often relies on mitochondrial DNA (mtDNA) barcoding, which can be intricate with recent histories of introgressive hybridization. The European green toad ( Bufotes viridis ) is characterized by cryptic phylogeographic subspecies and extensive cyto-nuclear discordance, particularly between European B. v. viridis and Asian B. v. sitibundus . Using an extensive reference dataset (2440 individuals from 730 localities) of two mtDNA genes, and haplotype-level analysis, we identified two well-established allochthonous green-toad populations in eastern and southern France. Both are assigned to B. v. viridis , despite distinct mitochondrial lineages: a typical viridis haplotype and a sitibundus haplotype largely associated with B. v. viridis ; their native distributions suggest independent origins. This case shows that mtDNA barcoding can remain informative when native diversity is well characterized and highlights green toads as a pioneer species highly adaptable to human-modified landscapes that warrants attention in bioinvasion monitoring.
Abstract Sexual dimorphism is a widespread evolutionary phenomenon across vertebrates, shaped by the combined effects of natural and sexual selection. In this study, we investigated sex-based morphological differences in the endangered Yellow-Spotted Mountain Newt ( Neurergus derjugini ) using a combination of traditional morphometrics and modern image-based analysis. A total of 394 adults individuals (102 females and 292 males) were photographed in the field, and dorsal images were analyzed to extract six phenotypic traits: body area, yellow spot area (%), total yellow spot area, average spot size, number of yellow spots, and spot circularity. Morphometric indices were computed using OpenCV-based segmentation and a convolutional neural network (EfficientNetB0) trained to distinguish body and spot regions. Statistical analyses revealed significant sexual dimorphism across all traits. Females had significantly larger body areas, consistent with fecundity-driven size dimorphism, while males exhibited greater yellow spot area relative to body size, more numerous and circular spots, suggesting a role for sexual selection. Principal component analysis (PCA) confirmed clear multivariate separation between sexes, emphasizing the multidimensional nature of sexual dimorphism. Our findings provide quantifiable, image-derived criteria for sex identification in N. derjugini and highlight the utility of automated phenotypic analysis in amphibian conservation. These methods offer scalable, non-invasive tools for population monitoring and contribute to a deeper understanding of morphological evolution in threatened species.
Abstract Tadpoles of some amphibian species exhibit morphological and colour changes in response to predators. In several Dryophytes species (Hylidae), dragonfly nymphs induce the development of a deep, vivid orange tail. Previous studies using clay models have demonstrated that dark tail spots can function as lures that divert predator attacks away from the body. However, whether bright orange tails have similar effects, particularly when tested on live individuals, remains unknown. Here, we exposed predator-induced (Orange) and non-induced (Normal) tadpoles of Dryophytes leopardus to dragonfly nymphs of Anax nigrofasciatus and analysed strike locations from recorded videos. We found that orange-coloured tails were attacked more frequently than bodies of Orange individuals or the tails of Normal ones. Mortality rates did not significantly differ between individual types (Orange or Normal) or body parts attacked, probably owing to the limited space for tadpoles to escape. Nevertheless, strikes to orange tails were more likely to fail and leave tadpoles uninjured than strikes to either the bodies of Orange individuals or the tails of Normal ones. These findings suggest that the orange tail functions not only as a lure but also as a potential deterrent to reduce strike accuracy, possibly via motion dazzle effects. Thus, the orange tail may serve purposes beyond being merely a disposable part. The limited occurrence of such conspicuous tail colouration among amphibians may be explained by ecological and physiological constraints, such as increased vulnerability to non-focal predators or the higher developmental costs of expressing orange colouration except under specific resource acquisition conditions.
Abstract Snakes introduced outside their native range are an emerging conservation concern because unnoticed populations may establish and impact native vertebrate communities. Here, we investigate two recent extra-range records of the western whip snake ( Hierophis viridiflavus ) in south-western Germany using mitochondrial DNA, phylogeographic network analyses, and local contextual information. Five samples from a waste dump population in Zweibrücken shared the same ND4 haplotype, belonging to a widespread Italian lineage, whereas a road-killed individual from Saarbrücken carried a previously undescribed haplotype of the western lineage. These results indicate two distinct origins. The Zweibrücken population is consistent with human-mediated introduction via long-distance waste transport from Italy, whereas the Saarbrücken record may reflect arrival from the nearby French range margin. Preliminary surveys suggest possible local impacts on native lizards. This case highlights waste movement as a potentially overlooked pathway for snake introductions, with ecological and sanitary implications.
Wall lizards (Podarcis spp.) of insular populations tend to tongue-flick at considerably lower rates than their conspecifics from the mainland when placed in a novel environment. It was suggested that this difference could result from differences in predation pressure, or in the social environment, with insular environments not requiring-or even penalizing-high investment in chemosensory sampling. To test whether the observed differences are genetic, or arise as a plastic response to the two types of environments, we raised Italian wall lizards (Podarcis siculus) from island and mainland origins in a common environment in the lab, and recorded their behaviour and tongue flick frequency in a novel situation. We found no differences in overall behaviour between progeny of mainland and island lizards, but individuals born from island parents tongue-flicked significantly less than those born from mainland parentage. This suggests that the difference in chemosensory scanning effort has a genetic basis. We argue that if the lower tongue-flick rates of island lizards reflect a reduced chemosensory capacity, this may constitute an interesting model system for the study of regressive evolution. Our results also raise the concern that the chemoreceptive languor of island lizards may make them extra vulnerable to the multitude of alien predators that is currently invading their homes.
When species that are reproductively incompletely isolated meet in parapatry and reproduce, a hybrid zone is established. The strength of reproductive isolation between these species and the dynamics of their ranges can be inferred from the extent and direction of gene flow across the hybrid zone. We determine the position, shape and dynamics of the relatively poorly studied hybrid zone between the Danube ( Triturus dobrogicus ) and Italian ( T. carnifex ) crested newts, using genome-wide nuclear DNA data (24 species-diagnostic SNPs) and an mtDNA marker (ND4). Overall, the hybrid zone is narrow, signifying strong selection against hybrids. In the north of the hybrid zone, asymmetric introgression of T. dobrogicus alleles into T. carnifex indicates postglacial expansion by T. carnifex . We also report a highly distinct haplotype lineage that presumably reflects ‘cryptic pseudogenes’; while the relevant sequences do not bear the hallmarks of a pseudogene, their apparent distinctiveness is not supported by an independent mtDNA marker (ND2).
In the face of a global biodiversity crisis, accurate estimates of population parameters-especially size and survival-are critical for effective conservation, yet such data are often scarce due to logistical, financial, and methodological challenges. Reptiles in Europe are particularly underrepresented in population studies. Although many are protected under the EU Habitats Directive, robust estimates of population density and survival exist for fewer than half of the listed species. In this study, we present a demographic assessment of the Italian wall lizard (Podarcis siculus) using capture-mark-recapture (CMR) methods. Fieldwork was carried out in 2019 at three distinct sites in Central and Southern Italy. We employed photographic identification combined with Jolly-Seber models to estimate population size, separately for males and females. Population densities showed marked spatial variation, ranging from 102 to 384 individuals per hectare. Apparent survival and detection probabilities also varied substantially, probably reflecting differences in local environmental conditions and habitat structure. These findings reveal significant demographic heterogeneity among populations, consistent with patterns observed in other Podarcis species. Our study demonstrates the applicability and reliability of CMR approaches for reptile monitoring and underscores the need for standardized long-term population data to inform conservation management. Importantly, these represent the first density estimates for P. siculus based on CMR, helping to address a major data gap for this species of conservation concern.
Snake conservation in Colombia is limited by the lack of information on ecological aspects and distribution ranges, particularly at the departmental level. Herein, we analyzed the state of knowledge of snakes in the department of Tolima, based on a thorough review of literature, and biological collection databases. We found 91 species documented either in literature (82) or museum collections (67). 24 species reported in literature are not supported by specimens in collections and nine species in museum collections don’t have been documented in the literature. We found a large gap in snake occurrence records throughout the department. Remarkably, 48 species reported for the department are outside of their current accepted distribution emphasizing the need of ID corroboration. There are only 35 snake species that have all the necessary information to corroborate their presence in the department, showing the need for a more thorough taxonomic effort to clearly define the actual snake richness. These results serve as a basis for future research and reflect the need to join efforts to characterize and understand the ophidian fauna of the department of Tolima and across Colombia.
Hybrid zones present a unique framework to study the genetic basis of reproductive isolation and speciation. The European fire-bellied toad (Bombina bombina) and yellow-bellied toad (B. variegata) hybridize in a zone across several thousand kilometres in Central Europe. The Bombina system has been examined for more than a century and its scientific legacy comprises the development of the ‘multilocus cline theory’ and the ‘maintenance of hybrid zones theory’. To set the scene for future genomic research we review the scientific literature on the Bombina hybrid zone, with emphasis on studies that provided insights into genetic processes. Our review emphasises that the two species are highly genetically diverged and reduced hybrid fitness prevents unrestricted gene flow between the two parental species (endogenous selection). However, environmental variables influence the location of hybrid populations (exogenous selection). Depending on region, the transects are described as clinal, tension, mosaic, and residual hybrid zones. The era of genomics has opened a plethora of yet unutilized analytical possibilities in Bombina research, including high resolution population genomics, understanding the genetic basis of reproductive isolation, phenotype-genotype associations, and elucidating the roles of endo- and exogenous selection in maintaining the hybrid zone. Because the hybrid zone occurs across many different environmental settings and genetic backgrounds, it should be possible to distinguish common genetic barriers to gene flow from those arising due to local adaptation. We argue that the Bombina zone offers an excellent opportunity to gain deep genomic insights into the selection processes that maintain the species boundary.
MtDNA barcoding is a powerful tool for determining the identity and provenance of introduced (cryptic) species. We mtDNA barcode Anguis slow worms from the Netherlands. We show that a non-native population (Zuid-Kennemerland National Park) that was established over a century ago concerns the same species that occurs natively: Anguis fragilis . It carries a haplotype that naturally occurs from The Netherlands to the Balkans. While a lineage from the Balkans up to Western Europe occurs throughout The Netherlands, we detect a lineage from France and Spain in one locality in the southwest of the country. We associate this record with the import of hay bales from France, used for horse feed. In the central Netherlands we find a haplotype previously only reported from Poland, potentially reflecting an unknown introduction or an underestimation of the haplotype’s distribution in the poorly sampled postglacially colonized part of the range.
Telmatobius is one of the most endangered genera globally. In the case of T. philippii, it has been classified as Critically Endangered by the IUCN, so advancing in its knowledge is a priority. We provide, for the first time, information on the trophic ecology of its tadpole, integrating information from gut content and analyzing the carbon S13C and nitrogen S15N isotopes. The tadpoles consumed a significant proportion of diatoms and invertebrates, with no discrimination in consumption according to developmental stages. A stable isotope analysis showed that the larvae mainly assimilated food of animal origin, explaining the trophic overlap with adults and sympatric Orestias fishes in energy resource use and trophic position. The results suggest overlap in the trophic niche of larvae and adults in these high-altitude environments.
Vipera ursinii rakosiensis is the most endangered venomous snake in Europe. Our information on the state of natural populations is somewhat limited apart from recent results indicating high genetic diversity in all of its three major areas in the Carpathian Basin. Developmental instability (DI) is a good indicator of environmental or internal perturbations an individual experiences during development, and fluctuating asymmetry (FA; random deviations from bilateral symmetry) is a good proxy for DI. We studied FA in head scale numbers in V. u. rakosiensis populations and contrasted it with the FA of other subspecies. The four V. u. rakosiensis populations showed similar FA levels. The FA in V. u. rakosiensis was higher than in the V. u. moldavica and V. u. ursinii populations, but similar to the V. u. macrops population. The (not exceptionally) high FA in V. u. rakosiensis might indicate external or internal stressors increasing DI. We suggest that FA should be monitored to get information on changes in DI.
In this essay I evaluate the use of passive integrated transponders (PIT-tags) for individual recognition in five sympatric populations of the large-bodied newts Triturus cristatus and T. marmoratus. Advice is given on how (not) insert PIT-tags. With pattern mapping applied in parallel, tag loss was shown to be absent or rare from live animals. Tags on the loose (i.e., without its carrier that presumably died and decomposed) were located in two ponds when these fell dry. Results suggest that aquatic T. marmoratus and juvenile T. cristatus experience higher natural mortality than adult cristatus. The long-term research on both species in the d & eacute;partement Mayenne, France may be paralleled by research sympatric Lissotriton helveticus and L. vulgaris, provided that miniature PIT-tags can justifiably be applied to these small bodied species.
