Hydromantes Research Articles

Interspecific and interpopulation variation in individual diet specialization: Do environmental factors have a role?

Individual diet specialization (IS) has important community- and population-level implications and its ecological drivers are actively investigated. Here, to test the hypothesis that local environmental conditions may influence IS in wild populations, we analyzed the stomach contents of 395 individuals from eight populations of five allopatric species of European cave salamanders (genus Hydromantes). We assessed whether their degree of individual diet specialization (1) scaled positively with the respective niche widths, in agreement with Van Valen's niche variation hypothesis (NVH), and (2) could be predicted by satellite-derived climatic and vegetation characteristics of the sites where the populations live. Consistent with the NVH, the degree of individual diet specialization increased with the populations' total niche width. Furthermore, two variables describing local nonarboreal vegetation cover and habitat heterogeneity successfully predicted the variation in individual specialization across the eight populations. Climatic factors had a generally low predictive power, with individual specialization in low- and high-elevation populations showing contrasting patterns of co-variation with air temperature in the warmest quarter of the year. However, independently from elevation, specialization peaked under conditions of high nonarboreal vegetation cover and high precipitation regimes. We discussed the results against two mutually nonexclusive scenarios hypothesizing different mechanisms linking environmental factors to salamanders' trophic strategy at an individual and population level. We concluded that satellite-derived climatic and vegetation variables to date generally adopted to model Grinnellian niches might also be useful in predicting spatial variations in dietary habits of populations, that is, their Eltonian niches.

Same Diet, Different Strategies: Variability of Individual Feeding Habits across Three Populations of Ambrosi’s Cave Salamander (Hydromantes ambrosii)

European cave salamanders of the genus Hydromantes are a group of eight species endemic to Italy and south-eastern France. Knowledge on the trophic niche of European Hydromantes is poor, and the few available studies only partially investigate their feeding habits. We performed an in-depth study on the trophic niche of the Ambrosi’s cave salamander (H. ambrosii), assessing the potential divergences among three different populations. All the populations had a similar diet composition, showing a wider trophic niche in fall compared to spring. In only one population, “true specialists” were present; however, in all three populations, generalist individuals always represented the larger proportion. Interspecific and intraspecific competition did not play an important role in determining individual dietary specialisation in H. ambrosii; contrarily, the characteristics of the surrounding environment seemed to be an important factor. The best body conditions were observed in the population located in the site where the non-arboreal vegetation cover was the highest. Besides providing new information on the trophic niche of H. ambrosii, we here showed that studies encompassing both intrinsic and extrinsic factors at the population level are needed to fully understand the trophic dynamics occurring among European cave salamanders.

On the stability of the dorsal pattern of European cave salamanders (genus Hydromantes)

Photographic identification is an emerging method for recognising wild animals. This harmless methodology allows researchers to identify “naturally marked” individuals and therefore study their specific ecology and behaviour. However, before incurring potential data loss, it is recommended to test the methodology on the target species and evaluate the pros and cons. We assessed the reliability of photographic identification in adult Hydromantes salamanders from three species. Specifically, we assessed whether the dorsal pattern of adult salamanders changed over time, thus evaluating its potential use as a reliable marking methodology. We used capture-mark-recapture and controlled conditions (i.e. individuals kept in fauna boxes) to evaluate potential changes in the dorsal pattern of Hydromantes through time. We did not observe any change in the dorsal pattern in the three species during the study period. Photographic identification might be a useful marking technique for these endangered species. However, these animals are usually found in environments generally lacking light and thus, researchers must be careful in setting up proper light conditions to produce suitable pictures for individual identification of Hydromantes.

Batracobdella leeches, environmental features and Hydromantes salamanders.

Leeches can parasitize many vertebrate taxa. In amphibians, leech parasitism often has potential detrimental effects including population decline. Most of studies on the host-parasite interactions involving leeches and amphibians focus on freshwater environments, while they are very scarce for terrestrial amphibians. In this work, we studied the relationship between the leech Batracobdella algira and the European terrestrial salamanders of the genus Hydromantes, identifying environmental features related to the presence of the leeches and their possible effects on the hosts. We performed observation throughout Sardinia (Italy), covering the distribution area of all Hydromantes species endemic to this island. From September 2015 to May 2017, we conducted >150 surveys in 26 underground environments, collecting data on 2629 salamanders and 131 leeches. Water hardness was the only environmental feature correlated with the presence of B. algira, linking this leech to active karstic systems. Leeches were more frequently parasitizing salamanders with large body size. Body Condition Index was not significantly different between parasitized and non-parasitized salamanders. Our study shows the importance of abiotic environmental features for host-parasite interactions, and poses new questions on complex interspecific interactions between this ectoparasite and amphibians.

THE NEUROHYPOPHYSIS OF URODELA: A COMPARATIVE ANALYSIS

SUMMARY In the Urodele amphibians the neurohypophysis shows different degrees of development. In Proteus, Ambystoma and Hydromantes, for instance, it consists of a thin lamina and the median eminence is poorly differentiated. In contrast, Triturus and Salamandra posses a thicker pars nervosa, and the median eminence is characterized by a functional stratification which does not substantially differ from that of other tetrapcds, e.g. the Anuran amphibians. In the Urodele neurohypophysis, inspection at the ultrastructural level reveals some relatively uniform features within the same group, e.g. as regards tanycytes, while other components may differ considerably between groups, such as (i) nerve fibre, types, identifiable on the basis of their content of granules and vesicles; (ii) the capillary arrangement; the development of the perivascular space and the relationships between nerve terminals and capillaries. In Hydromantes the neurohypophysial vessels, which may contain pericytes and nerve fibres, remai...

The enigmatic history of the European, Asian and American plethodontid salamanders

Recently published research addressing the question of relationships and biogeography of European plethodontid salamanders has refined time estimates for divergence from American relatives. The recently discovered Korean plethodontid Karsenia is either the sister-taxon of Hydromantes (which has members in Europe and California), or a close relative and co-member of a larger clade that originated in western North America, not eastern North America as formerly thought. The new information strengthens the biogeographical hypothesis that Hydromantes entered Eurasia via the Bering Land Bridge. Arguments are made favoring the placement of European and American relatives in a genus Hydromantes, with an American clade (subgenus Hydromantes) and a European clade (subgenera Atylodes and Speleomantes).

Phylogeography of Sardinian Cave Salamanders (Genus Hydromantes) Is Mainly Determined by Geomorphology

Detecting the factors that determine the interruption of gene flow between populations is key to understanding how speciation occurs. In this context, caves are an excellent system for studying processes of colonization, differentiation and speciation, since they represent discrete geographical units often with known geological histories. Here, we asked whether discontinuous calcareous areas and cave systems represent major barriers to gene flow within and among the five species of Sardinian cave salamanders (genus Hydromantes) and whether intraspecific genetic structure parallels geographic distance within and among caves. We generated mitochondrial cytochrome b gene sequences from 184 individuals representing 48 populations, and used a Bayesian phylogeographic approach to infer possible areas of cladogenesis for these species and reconstruct historical and current dispersal routes among distinct populations. Our results show deep genetic divergence within and among all Sardinian cave salamander species, which can mostly be attributed to the effects of mountains and discontinuities in major calcareous areas and cave systems acting as barriers to gene flow. While these salamander species can also occur outside caves, our results indicate that there is a very poor dispersal of these species between separate cave systems.

Cold‐blooded snipers: thermal independence of ballistic tongue projection in the salamander Hydromantes platycephalus

Plethodontid salamanders of the genus Hydromantes capture prey using the most extreme tongue projection among salamanders, and can shoot the tongue a distance of 80% of body length in less than 20 msec. The tongue skeleton is projected from the body via an elastic-recoil mechanism that decouples muscle contraction from tongue projection, amplifying muscle power tenfold. We tested the hypothesis that the elastic-recoil mechanism also endows tongue projection with low thermal dependence by examining the kinematics and dynamics of tongue projection in Hydromantes platycephalus over a range of body temperatures (2-24°C). We found that H. platycephalus maintained tongue-projection performance over the tested temperature range and that tongue projection showed thermal independence (Q(10) values of 0.94-1.04) of all performance parameters including projection distance, average velocity, and peak instantaneous values of velocity, acceleration, and power. Nonelastic, muscle-powered tongue retraction, in contrast, responded to temperature changes significantly differently than elastic tongue projection; performance parameters of retraction displayed thermal dependence typical of muscle-powered movement (Q(10) values of 1.63-4.97). These results reveal that the elastic-recoil mechanism liberates tongue projection from the effects of temperature on muscle contractile rates. We suggest that relative thermal independence is a general characteristic of elastic-recoil mechanisms and may promote the evolution of these mechanisms in ectothermic animals.

Lineage divergence and speciation in the Web-toed Salamanders (Plethodontidae: Hydromantes) of the Sierra Nevada, California

Peripatric speciation and the importance of founder effects have long been controversial, and multilocus sequence data and coalescent methods now allow hypotheses of peripatric speciation to be tested in a rigorous manner. Using a multilocus phylogeographical data set for two species of salamanders (genus Hydromantes) from the Sierra Nevada of California, hypotheses of recent divergence by peripatric speciation and older, allopatric divergence were tested. Phylogeographical analysis revealed two divergent lineages within Hydromantes platycephalus, which were estimated to have diverged in the Pliocene. By contrast, a low-elevation species, Hydromantes brunus, diverged from within the northern lineage of H.platycephalus much more recently (mid-Pleistocene), during a time of major climatic change in the Sierra Nevada. Multilocus species tree estimation and coalescent estimates of divergence time, migration rate, and growth rate reject a scenario of ancient speciation of H.brunus with subsequent gene flow and introgression from H.platycephalus, instead supporting a more recent divergence with population expansion. Although the small, peripheral distribution of H.brunus suggests the possibility of peripatric speciation, the estimated founding population size of the species was too large to have allowed founder effects to be important in its divergence. These results provide evidence for both recent speciation, most likely tied to the climatic changes of the Pleistocene, and older lineage divergence, possibly due to geological events, and add to evidence that Pleistocene glacial cycles were an important driver of diversification in the Sierra Nevada.

Phylogenetic relationships of Sardinian cave salamanders, genus Hydromantes, based on mitochondrial and nuclear DNA sequence data

The Tyrrhenian island of Sardinia is known for its high level of endemism. Beside the importance of this island as a refuge during the last glaciations, little is known about the origin and relationships of Sardinian species. Therefore, in an effort to resolve these relationships, in the current study we extended the existing dataset considerably by adding two nuclear genes and additional mitochondrial sequence data, as well as greatly extend the number of Sardinian populations represented in the dataset from eight to 16 populations.

Cytogenetic analysis of the Asian Plethodontid salamander, Karsenia koreana: Evidence for karyotypic conservation, chromosome repatterning, and genome size evolution

A cytogenetic analysis, including the karyotype, C-bands, silver-stained nucleolus organizer regions and genome size, was performed on the recently discovered species, Karsenia koreana, the first plethodontid salamander from Asia. The karyotype consists of 14 pairs of bi-armed chromosomes, with no evidence of heteromorphic sex chromosomes. C-banding reveals a concentration of heterochromatin at the centromeres as well as at interstitial locations. The smallest chromosome (pair number 14) has symmetrical interstitial C-bands in each arm, resembling chromosome no. 14 of North American species of its sister group taxon, supergenus Hydromantes. Acomparative analysis of C-band heterochromatin and silver-stained nucleolus organizer regions of Karsenia and other plethodontid genera reveals that chromosomal evolution may have featured chromosome 'repatterning' within the context of conserved chromosome number and shape in this clade. Genome size is correlated with geographic distribution in plethodontids and appears to have important phenotypic correlates as well. The genome size of Karsenia is relatively large, and resembles that of the geographically closest plethodontids from western North America, especially species of the genus Hydromantes. The biological significance of these cytogenetic characteristics of plethodontid salamanders is discussed within an evolutionary context.

Molecular Taxonomy of European Plethodontid Salamanders (Genus Hydromantes)

Genetic variation of 33 enzyme loci was analysed electrophoretically in 32 populations of the plethodontid genus Hydromantes from southern France, northern and central Italy, and Sardinia. Eight taxa were recognized, included in three groups: from the mainland, eastern Sardinia, and south-western Sardinia, respectively. In the mainland area, two semispecies were detected: H. italicus and H. ambrosii (sensu stricto), as well as a third species: H. strinatii (combinatio nova), previously included within H. ambrosii. Eastern Sardinian populations correspond genetically to three species: H. flavus, H. supramontis, and H. imperialis. In south-western Sardinia, two genetically differentiated but morphologically very similar groups were found within H. genei, whose specific status remains doubtful. The distinctness of a number of subspecific taxa (H. italicus gormani, H. i. ligusticus, H. i. argentatus, H. i. bonzanoi, H. genei funereus), is not supported by genetic evidence. Data from two contact zones in Italy indicate that taxa showing comparable levels of genetic differentiation (i.e., H. italicus-H. ambrosii s. s. and H. ambrosii s. s.-H. strinatii, both pairs with Nei's D about 0.4) have not reached the same level of reproductive isolation. On the basis of available data, attempts are made: (1) to interpret the present pattern of geographic distribution of European Hydromantes studied; (2) to explain their genetic relationships.

Cytogenetics of the European plethodontid salamanders of the genus Hydromantes (Amphibia, Urodela)

A karyological analysis was carried out on different European species of the genus Hydromantes (Plethodontidae). All the species examined share the same chromosome number (2n=28) and, with the exception represented by pair XIV, morphologically similar karyotypes. While the karyotypes display a similar distribution — mainly centromeric and pericentric — of C-heterochromatin, quantitative variations in pericentric heterochromatin are observed among species. In the continental species Hydromantes italicus and ambrosii as well as in the eastern Sardinian species imperialis, flavus and specie nova, pair XIV consists of heteromorphic sex chromosomes of the XX/XY type. It is proposed that the differentiation of the Y might have taken place through the occurrence of a structural rearrangement, such as a pericentric inversion, starting from a hypothetical, homomorphic pair XIV. A sex-related heteromorphism is not found in the western Sardinian species H. genei. A further karyological differentiation among these species concerns the position of the nucleolus organizing region (NOR), which is located on chromosome XII (H. italicus and ambrosii) or on chromosome X, close to the centromere (H. genei, H. imperialis and H. specie nova), or in an intercalary position (H. flavus). The location and the number of the 5 S DNA sites have been conserved during species divergence. On the basis of these karyological data, as well as of results obtained through a preliminary restriction enzyme analysis of the ribosomal and genomic DNAs, the phyletic relationships among the European Hydromantes species are discussed.

GENETIC DIFFERENTIATION, ALBUMIN EVOLUTION, AND THEIR BIOGEOGRAPHIC IMPLICATIONS IN PLETHODONTID SALAMANDERS OF CALIFORNIA AND SOUTHERN EUROPE.

The lungless salamanders, family Plethodontidae, are a group of over 200 species, placed in 23 genera, distributed mainly in the New World (Wake, 1966). The only Old World members of the family are Hydromantes italicus, from extreme southeastern France and northern and central Italy, and Hydromantes genei, from Sardinia (Thorn, 1968; Stefani, 1968; Bruno, 1973). The other members of this genus, Hydromantes brunus, Hydromantes shastae, and Hydromantes platycephalus, occur in California (Gorman, 1964a, 1964b). The extraordinary distribution of Hydromantes has attracted much attention. Even before Dunn (1923, 1926) placed European and American species in the genus Hydromantes, the former had been recognized as plethodontids, and speculations had been published concerning the origin of the disjunct distributional pattern and the possible reasons for the presence of so few plethodontids in the Old World (e.g., Scharff, 1911). Since the time of Dunn, the evolutionary relationships and biogeography of Hydromantes have been discussed by many authors (e.g., Noble, 1931; Adams, 1942; Schmidt, 1946; Mertens, 1951; Lanza, 1952; Gorman, 1956; Darlington, 1957; von WVahlert, 1957; Croizat, 1958; Wake, 1966; Stefani, 1968; Estes, 1970; Serra and Stefani, 1974). The consensus is that the European species are indeed plethodontids, and that the five European and American spe-

A New Cave Species of Salamander of the Genus Hydromantes from California, with Notes on Habits and Habitat

A New Cave Species of Salamander of the Genus Hydromantes from California, with Notes on Habits and Habitat

The Gularis Muscle in Aneides and Hydromantes

The Gularis Muscle in Aneides and Hydromantes