Lissotriton Helveticus Research Articles

Anthropogenic determinants of species presence in amphibian communities across a regional elevation gradient

AbstractIdentifying and quantifying the main factors that are jeopardizing amphibian communities worldwide is essential for planning effective amphibian conservation. We collected data on the presence/absence of salamanders and newts (Caudata) and frogs and toads (Anura) in >3600 water points from a large region (30,000 km2) in NW Spain during a 10‐year period (2004–2013). We contrasted a large set of hypotheses explaining presence/absence as a function of anthropogenic factors across the regional elevation gradient (1–2036 m). Logistic regression modeling revealed that salamanders and newts were mainly influenced by pollution and by land use changes, and that the effect of these factors changed with elevation. However, frogs and toads were affected by a larger set of factors acting synergistically, although not including land use changes, and their effect operated at all elevation ranges, except in the case of biological factors (invasive species and wild boar abundance) with higher effects at low elevation. Changes in land use was the most common factor at any elevation and included the abandonment of rural areas, which favors shrub and tree encroachment on former open land, and loss of water points. The most resilient species at any elevation were two frogs, Pelophylax perezi and Rana parvipalmata. The least resilient species were two salamanders, Chioglossa lusitanica and Lissotriton helveticus, followed closely by two toads, Alytes obstetricans and Pelobates cultripes. Unoccupied sites had higher frequencies of biological effects and of changes in land use in the first 5 years of study and lower frequencies of direct human influence factors in the second period. Overall, our results showed that the studied amphibian metacommunity was negatively influenced both by direct and indirect anthropogenic factors, but also that many amphibian species were not only capable of occupying sites which had been altered by human action, but were even favored by land uses generating open habitat, a habitat type that is increasingly uncommon in the region, in the entire Iberian Peninsula and in Europe.

Does habitat modification impact morphology, performance, and inflammatory responses in an amphibian with limited dispersal capacity (Lisssotriton helveticus)?

The environment of an organism exerts selective pressures that affect mobility, feeding, reproduction as well as predator-prey and conspecific interactions. Land use changes induced by human activities modify these selective pressures and may result in the adaptation of organisms. Amphibians are ectotherms that typically show a biphasic life cycle with an aquatic and terrestrial phase, which makes them particularly sensitive to environmental change. We studied the impact of habitat modifications on palmate newt populations in the Ile de France region across four types of habitats: urban, mixed, agricultural, and natural with at least two replicates for each habitat type. We measured the morphology of newts using callipers, quantified maximal running and swimming speed and acceleration using high-speed video recordings, and quantified the swelling of the hind limb linked to an inflammatory reaction. Our results show that in urban habitats, newts are larger and heavier and have a better body condition. Females, moreover, have a larger head in natural habitats, possibly due to diet specialisation of females during the breeding season. In mixed and agricultural habitats, newts have longer limbs and show a tendency to run faster, possibly associated with the selective pressures on movement in mixed habitats. Differences in inflammatory responses were observed between sexes but not habitat types. Overall, our results show differences in morphology and trends for differences in performance in newts living in different habitats suggesting that animals are adapting to human-induced changes in their environment.

Trophic effects of Bti-based mosquito control on two top predators in floodplain pond mesocosms

Chironomid (Diptera: Chironomidae) larvae play a key role in aquatic food webs as prey for predators like amphibian and dragonfly larvae. This trophic link may be disrupted by anthropogenic stressors such as Bacillus thuringiensis var. israelensis (Bti), a biocide widely used in mosquito control. In a companion study, we recorded a 41% reduction of non-target larval chironomids abundance in outdoor floodplain pond mesocosms (FPMs) treated with Bti. Therefore, we examined the diet of two top predators in the FPMs, larvae of the palmate newt (Salamandridae: Lissotriton helveticus) and dragonfly (Aeshnidae: predominantly Anax imperator), using bulk stable isotope analyses of carbon and nitrogen. Additionally, we determined neutral lipid fatty acids in newt larvae to assess diet-related effects on their physiological condition. We did not find any effects of Bti on the diet proportions of newt larvae and no significant effects on the fatty acid content. We observed a trend in Aeshnidae larvae from Bti-FPMs consuming a higher proportion of large prey (Aeshnidae, newt, damselfly larvae; ~42%), and similar parts of smaller prey (chironomid, mayfly, Libellulidae, and zooplankton), compared to controls. Our findings may suggest bottom-up effects of Bti on aquatic predators but should be further evaluated, for instance, by using compound-specific stable isotope analyses of fatty acids or metabarcoding approaches.

Extreme genetic depletion upon postglacial colonization hampers determining the provenance of introduced palmate newt populations

Abstract MtDNA barcoding is regularly applied to determine the provenance of invasive species. Variation in spatial genetic structuring across a species’ range, typically high within glacial refugia and low in postglacially colonized areas, influences the precision of this approach. The palmate newt (Lissotriton helveticus) has been introduced north of its native range inside the Netherlands. We conduct mtDNA barcoding to try and retrace the origin of the introduced localities. A large increase in sample size, particularly focusing on temperate Europe, emphasizes that the palmate newt shows practically no genetic variation outside the Iberian Peninsula glacial refugium. While we find a haplotype previously only known from the Iberian Peninsula inside the native range in Belgium, the haplotype present in the introduced Dutch populations occurs widely throughout the native range north of the Iberian Peninsula. Although mtDNA barcoding can be a powerful tool in invasion biology, the palmate newt case exposes its limitations.

An overview of the Scottish National Adder Survey 2022-24

A study was commissioned by NatureScot to analyse changes in the status of the adder (Vipera berus) and other native reptiles at 16 sites across mainland Scotland, the Isle of Skye and the Isle of Arran over a 30-year period from 1992-93 to 2022-24. In 2022-24, volunteer surveyors revisited sites that were previously surveyed in 1992-93 to identify changes in occupancy. Visual surveys recorded adder, common lizard (Zootoca vivipara), slow-worm (Anguis fragilis), common frog (Rana temporaria), common toad (Bufo bufo), smooth newt (Lissotriton vulgaris), and palmate newt (Lissotriton helveticus). Adders were observed in comparable or even greater numbers at eight sites (seven of the original sites surveyed in 1992-93), but an apparent loss of adders at three of the original sites, and major declines at a previously favourable site on the Scottish Borders are cause for concern. Of the other reptiles, common lizards were the most widespread, recorded at 12 sites; and slow-worms were least often recorded, in low numbers at only four sites, though this could be expected in visual surveys for this cryptic species. This publication reviews the factors most likely to be affecting adders in Scotland, particularly the loss of suitable habitat, the likely historic impact of persecution and the potential effects of disturbance by recreational site users. It highlights the importance of sympathetic habitat management, with a particular focus on maintaining favourable micro-habitats for reptiles.

Hitchhiking freshwater clams: First report of Sphaerium nucleus attached to Lissotriton helveticus in France

Hitchhiking freshwater clams: First report of Sphaerium nucleus attached to Lissotriton helveticus in France

Inconsistent estimates of hybridization frequency in newts revealed by SNPs and microsatellites

Hybridization between the European smooth and palmate newts has recurrently been mentioned in the literature. The only two studies that attempted to quantify the frequency of hybridization and gene admixture between these two species came to strikingly opposite conclusions. According to Arntzen et al. (1998, 42 allozymes), hybrids are rare in nature and introgression negligible, while according to Johanet et al. (2011, 6 microsatellites), introgressive hybridization is significant and widespread across the shared distribution range. To clarify this question, we implemented high-throughput SNP genotyping with diagnostic biallelic SNPs on 965 specimens sampled across Europe. Our results are in line with Arntzen et al., since only two F1 hybrids were identified in two distinct French localities, and no further hybrid generations or backcrosses. Moreover, reanalysis of 78 of the samples previously studied by Johanet et al. (2011) using our SNPs panel could not reproduce their results, suggesting that microsatellite-based inference overestimated the hybridization frequency between these two species. Since we did not detect methodological issues with the analyses of Johanet et al., our results suggest that SNP approaches outperform microsatellite-based assessments of hybridization frequency, and that conclusions previously published on this topic with a small number of microsatellite loci should be taken with caution, and ideally be repeated with an increased genomic coverage.

Coexistence of two newt species in a transition zone of range overlap

Abstract Theory suggests that spatial segregation of similar, co-occurring species may be driven by alternative innate life history and dispersal strategies, and that it operates through catastrophic events. An inventory of the evolutionary closely related small-bodied newts Lissotriton helveticus and L. vulgaris in the northwest of France demonstrated the species’ spatial partitioning, with L. vulgaris dominating in two pond-rich and historically disturbed coastal areas and L. helveticus prevailing inland where ponds are sparser. Population numbers were followed over several decades (1975–2021) in a pond within the narrow (ca. 2000 m wide) species transition zone. Early in the temporal survey (1986) a massive die-off was observed of two-third of the L. helveticus breeding population from a late frost event. Yet, the contribution of L. helveticus to the newt assemblage was more or less stable around 60%, even though the total population size fluctuated by an order of magnitude. Lissotriton vulgaris and a third species, Ichthyosaura alpestris, made up ca. 30% and 10% of the total till 1993, after which date their relative contributions reversed. These data suggest that a state shift may have occurred among the latter two species and that the assumed two-species dynamics of Lissotriton underlying the study has been an oversimplification. The local decline of L. vulgaris is paralleled by the loss of well-vegetated ponds from the wider agricultural terrain that affects this species more than L. helveticus and I. alpestris.

A lot of convergence, a bit of divergence: Environment and interspecific interactions shape body colour patterns in Lissotriton newts.

Coexistence with related species poses evolutionary challenges to which populations may react in diverse ways. When exposed to similar environments, sympatric populations of two species may adopt similar phenotypic trait values. However, selection may also favour trait divergence as a way to reduce competition for resources or mates. The characteristics of external body parts, such as coloration and external morphology, are involved to varying degrees in intraspecific signalling as well as in the adaptation to the environment and consequently may be diversely affected by interspecific interactions in sympatry. Here, we studied the effect of sympatry on various colour and morphological traits in males and females of two related newt species Lissotriton helveticus and L.vulgaris. Importantly, we did not only estimate how raw trait differences between species respond to sympatry, but also the marginal responses after controlling for environmental variation. We found that dorsal and caudal coloration converged in sympatry, likely reflecting their role in adaptation to local environments, especially concealment from predators. In contrast, aspects of male and female ventral coloration, which harbours sexual signals in both species, diverged in sympatry. This divergence may reduce opportunities for interspecific sexual interactions and the associated loss of energy, suggesting reproductive character displacement (RCD). Our study emphasizes the contrasting patterns of traits involved in different functions and calls for the need to consider this diversity in evolutionary studies.

Persistence of a population of palmate newts Lissotriton helveticus in a saline environment on the west coast of Scotland

A six year survey of a palmate newt (Lissotriton helveticus) population in rock pools on the west coast of Scotland indicates that this species has some tolerance of saline conditions. The newts were living with a mean salinity (conductivity) of 382 ppm (range 30.7 ppm to >4995 ppm). Other interesting observations include a variation in mating behaviour, in which normal open water behaviour is confined to crevices, and the occurrence of ‘pelvic bumps’ in some individuals that may indicate reduced body condition.

Population trends of four species of amphibians in western France; results from a 15 year time series derived from road mortality counts

Reports of declining amphibians are a major concern for conservation given their role as indicators of environmental change. This includes potentially impacting on the ecology other species and highlights the importance of monitoring long-term changes in amphibian populations. The core difficulty is gathering long term data sets that as well as being time consuming, may be costly and impractical for logistical reasons. Road mortalities have value in this respect since they are highly visible and have been frequently used as a metric to monitor changes in a variety of animal populations. In this paper they have been employed as proxies to estimate long-term population changes in four European species of amphibians. From January 2005 to December 2019 a total of 747 amphibian mortalities were recorded, the majority of which were urodeles. Most individuals were adults that entered roads during the annual migration period. Long term annual counts fluctuated widely in all species and peaked during the 4-year period from 2009 to 2012 with second period of high numbers in Triturus marmoratus and Hyla arborea during 2018 and 2019. Long-term population trends were evaluated using regression analysis of the logarithmic (loge) transforms of annual counts against year as independent variables, which were then tested against a hypothetical 0 regression coefficient, indicative of population stability. The results indicated long-term stability in T. marmoratus and H. arborea but potential declines in Lissotriton helveticus and Pelophylax lessonae, the latter showing metapopulation extinctions followed by recolonisation. Stepwise regression of potential climate drivers in amphibian numbers suggested a 2-year lag of rainfall during October and December were potential factors involved in population change.

A co‐development approach to conservation leads to informed habitat design and rapid establishment of amphibian communities

Abstract1. Effective wildlife restoration is a critical requirement of many conservation actions. The outcome of conservation interventions can be optimized through knowledge of species’ habitat requirements, but few studies consider the impact of using explicit evidence from dedicated local research to inform the design phase of habitat management. Furthermore, interventions administered externally from the top down, whilst simpler than those developed in discussion with multiple stakeholders including land managers (i.e. co‐development), run the risk of failing to engage local people.2. In this study, we focus on interventions in the Scottish Highlands to improve the availability and suitability of breeding ponds for local amphibian assemblages. We collected and analysed data based on 129 ecological variables across 88 reference ponds to quantify the local habitat preferences. We used the findings from these analyses to inform the construction or restoration of 25 intervention ponds co‐developed in partnership with stakeholders (landowners, foresters, citizen scientists and government agencies). Following the interventions, we monitored amphibian communities at these sites over 4 years. We assessed presence and abundance of all five native amphibians (the anurans Rana temporaria and Bufo bufo, and the salamanders Lissotriton helveticus, L. vulgaris and Triturus cristatus) using egg searching, dip‐netting, torching and trapping.3. The new habitats were overall characterized by ecological conditions more favourable to amphibians than the reference ponds. We recorded a total of 51 colonization events. Within two breeding seasons after construction or restoration, the intervention ponds hosted the full complement of species, mirroring amphibian diversity patterns found in the local reference ponds.4. Our study shows that ecological research to quantify local habitat requirements and working with commercial landmanagers to ensure equitable benefits prior to designing conservation actions can promote rapid and efficient recovery of wildlife.

Progenesis as an intrinsic factor of ecological opportunity in a polyphenic amphibian

Abstract Paedomorphosis, a developmental heterochrony involving the retention of larval traits at the adult stage, is considered a major evolutionary process because it can generate phenotypic variation without requiring genetic modifications. Two main processes underlie paedomorphosis: neoteny, a slowdown of somatic development, and progenesis, a precocious maturation associated with body size reduction. Being essentially a truncation of ontogeny, progenesis has often been deemed an evolutionary dead end with advantages attributed to precocious reproduction or small body size required in specific environmental contexts (e.g. parasitism, interstitial life), but there is a lack of studies on the immediate ecological consequences of progenesis. Because body size is a key factor determining trophic ecology in animals, we hypothesized that progenesis might intrinsically promote ecological opportunity via body size reduction (i.e. ‘the trophic advantage of progenesis’ hypothesis). We tested this hypothesis in facultatively progenetic palmate newts Lissotriton helveticus using stable isotope niche modelling and diet reconstruction in conjunction with traditional stomach content analyses and body condition (BC) assessment. We show that not only did progenetic individuals occupy a different trophic niche than metamorphic individuals in all populations, but the smaller they were compared to metamorphs due to progenesis, the more different they were in terms of trophic ecology, with no negative effect on their BC. Altogether, the results suggest that via body size reduction, progenesis may generally act as an intrinsic factor of ecological opportunity, allowing the use of existing but previously unavailable resources, even in habitats where seemingly little opportunity exists. We argue that beyond the classically recognized fitness advantages of progenetic development, this process may also generally bring an immediate trophic advantage via body size reduction, which would have important implications to understand the evolution and adaptiveness of this process in many different taxa, from marine meiofauna to primates. A free Plain Language Summary can be found within the Supporting Information of this article.

A reference DNA barcode library for Austrian amphibians and reptiles.

In the last few years, DNA barcoding became an established method for species identification in biodiversity inventories and monitoring studies. Such studies depend on the access to a comprehensive reference data base, covering all relevant taxa. Here we present a comprehensive DNA barcode inventory of all amphibian and reptile species native to Austria, except for the putatively extinct Vipera ursinii rakosiensis and Lissotriton helveticus, which has been only recently reported for the very western edge of Austria. A total of 194 DNA barcodes were generated in the framework of the Austrian Barcode of Life (ABOL) initiative. Species identification via DNA barcodes was successful for most species, except for the hybridogenetic species complex of water frogs (Pelophylax spp.) and the crested newts (Triturus spp.), in areas of sympatry. However, DNA barcoding also proved powerful in detecting deep conspecific lineages, e.g. within Natrix natrix or the wall lizard (Podarcis muralis), resulting in more than one Barcode Index Number (BIN) per species. Moreover, DNA barcodes revealed the presence of Natrix helvetica, which has been elevated to species level only recently, and genetic signatures of the Italian water frog Pelophylax bergeri in Western Austria for the first time. Comparison to previously published DNA barcoding data of European amphibians and reptiles corroborated the results of the Austrian data but also revealed certain peculiarities, underlining the particular strengths and in the case of the genus Pelophylax also the limitations of DNA barcoding. Consequently, DNA barcoding is not only powerful for species identification of all life stages of most Austrian amphibian and reptile species, but also for the detection of new species, the monitoring of gene flow or the presence of alien populations and/or species. Thus, DNA barcoding and the data generated in this study may serve both scientific and national or even transnational conservation purposes.

Winter presence of adult male palmate newts (Lissotriton helveticus) in a pond in Scotland

Winter presence of adult male palmate newts (Lissotriton helveticus) in a pond in Scotland

Mosquito control based on Bacillus thuringiensis israelensis (Bti) interrupts artificial wetland food chains

The biocide Bacillus thuringiensis israelensis (Bti) has become the most commonly used larvicide to control mosquitoes in seasonal wetlands. Although Bti is considered non-toxic to most aquatic organisms, the non-biting chironomids show high susceptibilities towards Bti. As chironomids are a key element in wetland food webs, major declines in their abundance could lead to indirect effects that may be passed through aquatic and terrestrial food chains. We conducted two mesocosm experiments to address this hypothesis by assessing direct and indirect effects of Bti-modified availability of macroinvertebrate and zooplankton food resources on the predatory larvae of palmate and smooth newts (Urodelans: Lissotriton helveticus, Lissotriton vulgaris). We examined newt survival rates and dietary composition by means of stable isotope (δ15N and δ13C) analysis in the presence of Bti treatment and a predator (Odonata: Aeshna cyanea). We assessed palmate newts' body size at and time to metamorphosis while developing in Bti treated mesocosms. Chironomid larvae were the most severely affected aquatic invertebrates in all Bti treated food chains and experienced abundance reductions by 50 to 87%. Moreover, stable isotope analysis revealed that chironomids were preferred over other invertebrates and comprised the major part in newts' diet (56%) regardless of their availability. The dragonfly A. cyanea decreased survival of newt larvae by 27% in Bti treated mesocosms showing affected chironomid abundances. Increasing intraguild predation is most likely favored by the Bti-induced reduction of alternative prey such as chironomid larvae. The decreased food availability after Bti treatment led to slightly smaller L. helveticus metamorphs while their developmental time was not affected. Our findings highlight the crucial role of chironomids in the food webs of freshwater ecosystems. We are also emphasizing the importance of reconsidering human-induced indirect effects of mosquito control on valuable wetland ecosystems particularly in the context of worldwide amphibian and insect declines.

Reproductive fitness consequences of progenesis: Sex-specific pay-offs in safe and risky environments.

Progenesis is considered to have an important role in evolution because it allows the retention of both a larval body size and shape in an adult morphology. However, the cost caused by the adoption of a progenetic process in both males and females remains to be explored to explain the success of progenesis and particularly its biased prevalence across the sexes and environments. Here, through an experimental approach, we used a facultative progenetic species, the palmate newt (Lissotriton helveticus) that can either mature at a small size and retain gills or mature after metamorphosis, to test three hypotheses for sex-specific pay-offs of progenesis in safe versus risky habitats. Goldfish were used because they caused a higher decline in progenetic than metamorphic newts. We determined that progenetic newts have a lower reproductive fitness than metamorphic newts. We also found that, when compared to metamorphs, progenetic males have lower reproductive activity than progenetic females and that predatory risk affects more progenetic than metamorphic newts. By identifying ultimate causes of the female-biased sex ratios found in nature, these results support the male escape hypothesis, that is the higher metamorphosis rate of progenetic males. They also highlight that although progenesis is advantageous in advancing the age at first reproduction, it also brings an immediate fitness cost and this, particularly, in hostile predatory environments. This means that whereas some environmental constraints could favour facultative progenesis, some others, such as predation, can ultimately counter-select progenesis. Altogether, these results improve our understanding of how developmental processes can affect the sexes differently and how species invasions can impair the success of alternative developmental phenotypes.

The role of predation risk in metamorphosis versus behavioural avoidance: a sex-specific study in a facultative paedomorphic amphibian

Evolutionary theory predicts the evolution of metamorphosis over paedomorphosis (the retention of larval traits at the adult stage) in response to life in unfavourable habitats and to the benefits of dispersal. Although many organisms are canalised into obligatory complex or simple life cycles, some species of newts and salamanders can express both processes (facultative paedomorphosis). Previous research highlighted the detrimental effect of fish on both metamorphic and paedomorphic phenotypes, but it remains unknown whether predation risk could induce shifts from paedomorphosis to metamorphosis, whether behavioural avoidance could be an alternative strategy to metamorphosis and whether these responses could be sex-biased. Testing these hypotheses is important because metamorphosed paedomorphs are dispersal individuals which could favour the long-term persistence of the process by breeding subsequently in more favourable waters. Therefore, we quantified the spatial behaviour and timing of the metamorphosis of facultative paedomorphic palmate newts Lissotriton helveticus in response to predation risk. We found that fish induced both male and female paedomorphs to hide more often, but behavioural avoidance was not predictive of metamorphosis. Paedomorphs did not metamorphose more in the presence of fish, yet there was an interaction between sex and predation risk in metamorphosis timing. These results improve our understanding of the lower prevalence of paedomorphs in fish environments and of the female-biased sex ratios in natural populations of paedomorphic newts. Integrating sex-dependent payoffs of polyphenisms and dispersal across habitats is therefore essential to understand the evolution of these processes in response to environmental change.

Variable effects of an invasive species on the reproduction and distribution of native species in pond networks

Abstract The arrival of non‐native species in a community can be deleterious for native species. The joint investigation of several descriptors of native populations susceptible to invaders, under different invasion contexts, may help in predicting the outcome of their co‐occurrence with invasive species. Moreover, empirical studies seldom document the relative importance of the effects of invasive species on native species compared with other factors. Using survey data, we evaluated whether reproduction (larval density) and distribution of breeding sites of three amphibian species (Rana dalmatina, Lissotriton helveticus, and Triturus marmoratus) were related to the presence of invasive red swamp crayfish Procambarus clarkii, compared to other native predators, habitat, and landscape features, in two pond networks that differed in invasion intensity. The red swamp crayfish was only negatively associated with the larval density of one amphibian species studied. Its effect size was similar to that of some native predators, and much smaller than that of the canopy cover of ponds. Amphibians were widespread in the two pond networks. The occupancy of only one species in each network was negatively related to crayfish presence, while the occupancy of all species was negatively related to fish presence. The distribution of amphibian breeding sites was positively associated with aquatic vegetation cover. Negative associations between amphibians and red swamp crayfish were detected only in a few cases, even in the most invaded area, and thus results were less alarming than in previous studies. Differences in ecological traits of native amphibians and interactions with other environmental factors may explain the variable effects of red swamp crayfish on native amphibian populations.

Context-dependent dispersal, public information, and heterospecific attraction in newts.

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.