Water Frogs Research Articles

Update on the herpetofauna of Syros (Cyclades, Greece) and current land-use and climate change threats

The current knowledge on the herpetofauna of Syros is updated, whereby no publications on it have been made since 1975. I provide the results from a field trip in 2024 that focused on the hygrophilous species. The Balkan Water Frog and the Balkan Terrapin, mentioned for Syros in the 19th century, meanwhile have become extinct. The Green Toad is threatened with extinction, the status of the Grass Snake is unclear. The Green Toad has benefited previously from anthropogenic spawning grounds in the form of open cisterns, which have fallen into disuse and thus are no longer available to the amphibians. The ongoing climate change in the Aegean region is reflected in drier winters, which dry out water bodies. The situation for the wetlands and their fauna and flora on Syros is alarming.

Lethal grip for an endangered endemic frog: The freshwater crab Potamon karpathos (Decapoda, Potamidae) preys on Karpathos water frog Pelophylax cerigensis (Anura, Ranidae)

Invertebrate predation on amphibians is widespread, although unreported in Europe. Here, we present documented predation of the Karpathos water frog (Pelophylax cerigensis) by the crab Potamon karpathos. Pelophylax cerigensis is an endangered, endemic species exclusively found on the Rhodes and Karpathos Islands in the South Aegean Sea, Greece. The Karpathos population is at risk due to limited suitable habitats and a scarcity of freshwater bodies on the island. From April to October, when there is no rain on the island, frogs and crabs cohabitate, sharing the same shallow ditches. Incidents of frog predation by crabs are common, indicated by numerous individuals with amputated limbs and scars, representing an additional threat to the endangered frog. Further research on the interactions between the two species is urgently required, as it has direct conservation implications.

Inheritance patterns of male asexuality in hybrid males of a water frog Pelophylax esculentus.

Gametogenesis produces gametes as a piece of genetic information transmitted to the offspring. While during sexual reproduction, progeny inherits a mix of genetic material from both parents, asexually reproducing organisms transfer a copy of maternal or paternal DNA to the progeny clonally. Parthenogenetic, gynogenetic and hybridogenetic animals have developed various mechanisms of gametogenesis, however, their inheritance is not fully understood. Here, we focused on the inheritance of asexual gametogenesis in hybrid Pelophylax esculentus (RL), emerging after crosses of P. lessonae (LL) and P. ridibundus (RR). To understand the mechanisms of gametogenesis in hybrids, we performed three-generation experiments of sexual P. ridibundus females and hybrids from all-male hybrid populations. Using fluorescent in situ hybridization, micronuclei analysis, flow cytometry and genotyping, we found that most adult hybrid males simultaneously produced two types of clonal sperm. Also, most male tadpole progeny in two successive backcrossed generations simultaneously eliminated L and R parental genomes, while some progeny produced only one type of sperm. We hypothesize that the reproductive variability of males producing two kinds of sperm is an adaptive mechanism to reproduce in mixed populations with P. ridibundus and may explain the extensive distribution of the all-male lineage across the European River Basin.

Hidden in the frog: morphological and molecular characterization of Halipegus ovocaudatus (Platyhelminthes: Trematoda), type species of the genus Halipegus Looss, 1899.

The type species of the genus Halipegus Looss, 1899, Halipegus ovocaudatus (Vulpian, 1859) is a generalist parasite of different species of amphibians, mainly anurans. To date, the phylogenetic position of this species has not been established. Specimens of H. ovocaudatus, were collected from three species of water frogs, Pelophylax ridibundus (Pallas), P. esculentus (Linnaeus), and P. lessonae (Camerano) inhabiting the Middle Volga region (European Russia). In our study, we provide detailed morphological redescription of these digeneans and combine it with molecular phylogenetic analyses based on partial sequences of the 28S rDNA and coI mtDNA genes. The phylogenetic position of H. ovocaudatus among the derogenids has been established as a sister clade to other representatives of the Halipeginae. We compared pairwise distances based on partial sequences of coI mtDNA genes of H. ovocaudatus and other representatives of Derogenidae. It was shown, that adults of H. ovocaudatus from different hosts are representatives of the same species. Specimens parasitizing three frog hosts from several localities differ slightly in body shape and size, which probably reflects host-induced intraspecific variability.

Parental care of underwater egg clutches in Andean water frogs (Anura: Telmatobiidae)

The most generalized reproductive mode in anurans is the deposition of egg clutches in water that develop into exotrophic aquatic tadpoles. Yet, despite this extended distribution, cases of parental care on submerged egg clutches are poorly documented. Because of its high diversity, its aquatic habits, and reports on males of two species standing next to the clutch, the Andean genus Telmatobius Wiegmann, 1834 offers an excellent model to examine the evolution of such behavior and the factors influencing it. Here, we combine field and laboratory studies to describe the breeding biology and parental care behavior on Telmatobius culeus (Garman, 1876), Telmatobius hintoni Parker, 1940, Telmatobius intermedius Vellard, 1951, Telmatobius jelskii (Peters, 1873), and Telmatobius oxycephalus Vellard, 1946. Our findings indicate that these five species have prolonged breeding season, and use concealed underwater shelters between rocks or macrophytes for mating and egg deposition. We showed that clutches of 35–560 eggs are deposited in these shelters. Males were observed next to the egg clutch and defending it aggressively against intruders, including conspecifics. Females were, on average, larger than males supporting the hypothesis that competition among males does not drive sexual size dimorphism in the genus. Our findings provide meaningful data to use in conservation programs, given that most species of Telmatobius are considered endangered and fill a significant information gap in understanding parental care’s origin in Nobleobatrachia.

Blood parasites of water frogs (Pelophylax esculentus complex) from the Danube Delta, Romania

Water frogs of the genus Pelophylax host a variety of parasites, from protozoa to helminths. Among the blood parasites, representatives of Apicomplexa, Trypanosoma and Nematoda show the highest prevalence. In this study, we focused on blood parasites of water frogs living in the Danube Delta, Romania. In total, 74 individuals of P. ridibundus and eight individuals of P. esculentus from six localities were examined. Blood parasites were detected microscopically and using a molecular marker (18S rDNA). 89.77% of frogs from all investigated localities were found to be infected with at least one parasitic group, specifically with haemogregarines (84.09%), nematodes (1.14%), and trypanosomes (63.64%). The parasitemia of haemogregarines and trypanosomes differed significantly among the studied locations. There was no statistically significant difference in parasitemia between male and female hosts. However, adults were found to have a significantly higher parasitemia in comparison with subadults infected with haemogregarines. Correlation between parasitemia and the body length of frogs infected with haemogregarines was also significant (r = 0.226). By comparing the 18S rDNA sequences with the corresponding GenBank sequences, Hepatozoon species identified in water frogs showed a close similarity (98.1–99.8%) to Hepatozoon magna. Trypanosomes showed the highest sequence similarity to Trypanosoma sp. isolate R10 clone L2–3, Trypanosoma ranarum, and Trypanosoma cobitis.

The immunolocalization of adiponectin and its receptors in the testis of the frog Pelophylax bergeri

In all vertebrates, reproductive strategies are achieved by modulation of the neuroendocrine system in a similar manner and with minor variations among the different classes. Most of the available information on amphibian testicular cycles derive from anurans, and among these, water frogs have been extensively studied in terms of reproductive mechanisms and sex steroid correlation. Adiponectin (AdipoQ) and its receptors—AdipoR1 and AdipoR2—are essential for most of the normal testicular and sperm functions. In this study, the identification of AdipoQ and its two receptors was carried out by immunohistochemistry in the testis of adult males of Pelophylax bergeri. The AdipoQ system was observed in the frog spermatogenic cysts, in both germinal and Sertoli cells, as well as in the rete testis. AdipoQ and AdipoR1 were localized in germ-line cells, from spermatogonia to round spermatids, while AdipoR2 was detected in the elongated spermatids, spermatozoa, and Sertoli cells. AdipoR1 was also observed in the intratesticular canals of the rete testis. This preliminary study shows the AdipoQ system’s presence in the anurans’ testis. The results obtained could be a starting point for future functional studies aimed at defining the physiological role of the AdipoQ system in frog testicular functions.

Predation by a Mountain Caracara on a Titicaca Water Frog in Peru

Predation by a Mountain Caracara on a Titicaca Water Frog in Peru

Which species of water frogs inhabit ponds of the Caucasus? Taxonomic mess with Pelophylax ridibundus species complex

Two nominal species of water frogs of the genus Pelophylax, P. ridibundus and P. bedriagae, are found in Central and Eastern Europe, the Middle East, Western Asia, Western Kazakhstan, and Siberia. So far, the taxonomic status of Pelophylax in most of the Caucasus has remained unknown. Sequencing of the Cytochrome Oxidase 1 mitochondrial gene attributed the frogs throughout Georgia to the P. ‘bedriagae’ lineage, bringing them very close to the specimens from Kazakhstan and Greece. Simultaneously, the current nomenclature of water frogs appears to be formally incorrect since western Kazakhstan, the type locality for P. ridibundus, has frogs genetically closer to nominal P. bedriagae, than to nominal P. ridibundus from Europe. Because there is no evidence that the frogs from Central Europe, Kazakhstan, and the Caucasus, as well as from Anatolia and Iran, are biological species with individual evolutionary pathways, we suggest a conservative approach and synonymize nominal P. bedriagae from most of West Asia with P. ridibundus.

Piecing the barcoding puzzle of Palearctic water frogs (Pelophylax) sheds light on amphibian biogeography and global invasions.

Palearctic water frogs (genus Pelophylax) are an outstanding model in ecology and evolution, being widespread, speciose, either threatened or threatening to other species through biological invasions, and capable of siring hybrid offspring that escape the rules of sexual reproduction. Despite half a century of genetic research and hundreds of publications, the diversity, systematics and biogeography of Pelophylax still remain highly confusing, in no small part due to a lack of correspondence between studies. To provide a comprehensive overview, we gathered >13,000 sequences of barcoding genes from >1700 native and introduced localities and built multigene mitochondrial (~17 kb) and nuclear (~10 kb) phylogenies. We mapped all currently recognized taxa and their phylogeographic lineages (>40) to get a grasp on taxonomic issues, cyto-nuclear discordances, the genetic makeup of hybridogenetic hybrids, and the origins of introduced populations. Competing hypotheses for the molecular calibration were evaluated through plausibility tests, implementing a new approach relying on predictions from the anuran speciation continuum. Based on our timetree, we propose a new biogeographic paradigm for the Palearctic since the Paleogene, notably by attributing a prominent role to the dynamics of the Paratethys, a vast paleo-sea that extended over most of Europe. Furthermore, our results show that distinct marsh frog lineages from Eastern Europe, the Balkans, the Near East, and Central Asia (P. ridibundus ssp.) are naturally capable of inducing hybridogenesis with pool frogs (P. lessonae). We identified 14 alien lineages (mostly of P. ridibundus) over ~20 areas of invasions, especially in Western Europe, with genetic signatures disproportionally pointing to the Balkans and Anatolia as the regions of origins, in line with exporting records of the frog leg industry and the stocks of pet sellers. Pelophylax thus emerges as one of the most invasive amphibians worldwide, and deserves much higher conservation concern than currently given by the authorities fighting biological invasions.

Nuclear gene introgressions in hybrid populations of water frog Pelophylax esculentus complex: geographical analysis of the phenomenon and its interpretation.

Reproduction of water frog hybrids Pelophylax esculentus (Pelophylax ridibundus x Pelophylax lessonae) is associated with hemiclonal reproduction and backcrossing. The hemiclonal mode of reproduction occurs within P. esculentus allodiploids. In this case, the unrecombined genome of one parental species is transmitted to the offspring after premeiotic elimination of the chromosome set of the second parental species. Usually, the chromosome set of P. lessonae is eliminated, and the altered genome of P. ridibundus is passed on to the progeny. The hemiclonal inheritance within diploid Pelophylax esculentus hybrids may be accompanied by certain aberrations of premeiotic elimination. As a result, the formation of P. ridibundus specimens with introgressions of the P. lessonae genetic material, or the formation of recombinant hybrids occurs, depending on which of the parental species backcrossing takes place. The aim of our study is to describe the aberration of premeiotic elimination within the water frog P. esculentus complex detected by the nuclear gene Ldh-B inheritance, with an attempt to find out the causes of this phenomenon. It has been established that aberrations of premeiotic elimination are widespread, but only within populations of water frog from the river system of Upper Dnieper within Ukraine. The highest level of introgression takes place in the water frog populations within Kiev metropolis under conditions of expressed anthropogenization, while the maximum frequency of recombinants was detected within populations from the basin of Desna River, that has preserved native ecosystems. It was demonstrated that the frequency of premeiotic aberrations does not correlate with the intensity of interspecific water frog hybridization. Populations with introgressions are more common than populations with recombinants, however, within the latter, the frequency of recombination events is higher. The primary factor of gametogenesis aberrations, most likely, is the genetic characteristics of the local populations of parental species, since unambiguous explanations of this phenomenon based on the action of environmental stress (pollution of water systems) are not obvious.

Far from home: tracing the origin of non-native water frogs (genus Pelophylax) in Malta by molecular markers

AbstractOne of the most frequently translocated species outside their native range in Europe are water frogs of the genus Pelophylax. Recently, water frogs belonging to the same genus have also been recorded on the island of Gozo in Malta. To trace their origin, we genetically examined 17 individuals from three Gozitan localities where water frogs have been recorded recently. We analysed one mitochondrial (NADH dehydrogenase 2, ND2) and one nuclear (serum albumin intron 1, SAI-1) fragment to identify the geographic origin of the frogs and a set of microsatellite markers to determine their population-genetic structure and the predicted number of source populations. Based on the ND2 and SAI-1 markers, the water frogs on the island of Gozo originate from southern Anatolia, Turkey. According to sequence variation in ND2, they were assigned to a caralitanus mtDNA clade, which is endemic to southern Anatolia and taxonomically represents either an evolutionary lineage within P. cf. bedriagae or a separate species P. caralitanus. All Gozo water frogs had only one haplotype in the ND2 and one allele in the SAI-1 fragment, indicating a recent and single introduction event. These results are supported by microsatellite analysis, which revealed low genetic variability and the absence of any population-genetic structure, suggesting that Gozo water frogs originate from only one source population.

Investigation of heavy metals in tissues and habitats of three edible frogs from Türkiye.

The soil, water, and organisms have been contaminated by heavy metals due to human activities and industrialization, which has produced a major environmental problem that has a deleterious effect on human health and food quality. Frogs, one of the good bioindicators for environmental pollution, are also among the alternative essential protein sources for humans. In Türkiye, three of these frogs are edible: Pelophylax ridibundus, Pelophylax bedriagae, and Pelophylax caralitanus, also known as Anatolian water frogs. Hence, to assess the possible health risks that might result from consuming frog legs in addition aquatic habitat of Anatolian water frogs, the water, sediment, and frog tissue samples (muscle and liver) were obtained from 11 different provinces covering all regions of Türkiye and analyzed to determine Cd, Cu, Cr, Zn, Pb, and As concentrations. The results revealed considerable variations in heavy metal concentrations among frog tissues, influenced by the sampling sites and species (ANOVA: p < 0.05). The Estimated Daily Intake (EDI) values, calculated based on the average serving size, were also lower than the Provisional Tolerable Daily Intake (PTDI) levels for adult consumers. Furthermore, the study computed the Target Hazard Quotient (THQ) values for heavy metals, all of which were below the critical value of 1, indicating that consuming the hind leg muscles from these frog species would not pose an adverse health risk for humans.

Decline of Pelophylax lessonae in mixed populations of water frogs over the last 50 years

Two water frog species: the pool frog Pelophylax lessonae (L) and the marsh frog P. ridibundus (R) occur sympatrically in Central Europe and form mixed populations (genetic systems) with their hybrid, the edible frog P. esculentus (E). The aim of the study was to assess the species composition of water frogs in urban and rural populations and compare our current findings with the results of previous studies. We surveyed the same sites that were investigated by Berger et al. in 1962–1970 (Poznań, urban landscape) and 1977–1997 (Dezydery Chłapowski Landscape Park, rural landscape). Because some ponds surveyed in the past were destroyed or dried-up, we also explored others located in the adjacent areas. We captured frogs during breeding seasons 2020 and 2021 and identified them by the nuclear marker gene SAI-1. We found three types of populations in the urban area: R-E, E-E and R-E-L and four in the rural area: R-E, L-E, E-E and R-E-L. Compared to the historical data, we found a drastic decrease in the frequency of P. lessonae in urban and rural landscapes: from 89.1% and 68% to 2.7% and 1.8%, respectively. At the same time, the frequency of P. ridibundus increased from 2.2% and 0.1% to 40% and 29.6%, respectively. A similar pattern was found for P. esculentus whose frequency increased from 8.7% and 31.9% to 57.3% and 68.6%, respectively. Additionally, we confirmed the presence of a cryptogenic Balkan water frog, P. kurtmuelleri, which was recently discovered in south-western Poland. The frequency of SAI-1 allele specific for this taxon reached 7.3%. The patterns found in both types of landscapes are in line with the current situation of both parental species in Europe. Such dynamic changes show the need for long-term monitoring of the population compositions of water frogs, what is crucial for their conservation management.

A new early water frog (Telmatobius) from the Miocene of the Bolivian Altiplano

AbstractWe describe the new frog Telmatobius achachila sp. nov. from the late Middle to earliest Late Miocene of Achiri, based on a partial skeleton found at 3960 m above sealevel in the Bolivian Altiplano. This skeleton, attributed to a male adult, constitutes the first documented fossil record of the speciose living genus Telmatobius, endemic to the Andean Cordillera and the Altiplano. Phylogenetic analysis confirms the new species as being part of the crown group, and diverging both later than the T. verrucosus group and earlier than the T. bolivianus, T. marmoratus and T. macrostomus groups. Coupled with its accurate stratigraphic provenance and age, this phylogenetic position provides a relevant calibration point for timing the evolutionary history of these highland, mostly aquatic frogs. The skeleton of T. achachila indicates that several of the osteological peculiarities of extant Telmatobius were already acquired at c. 12 Ma, including some that might be linked to their aquatic lifestyle. Together with mixed montane–rainforest pollen vegetation uncovered in the same level, this fossil specimen further provides key data enabling a more accurate reconstruction of ancestral habitats and elevation ranges of Telmatobius, agreeing with the previously postulated conditions in which these water frogs might have first evolved. Ultimately, this discovery adds to the sparse evidence of a humid tropical Bolivian Altiplano just prior to: (1) the Late Miocene uplift pulse of the Central Altiplano; and (2) the drastic climate deterioration that occurred from Late Miocene time onward, leading to the harsh highland‐steppe environments reigning there today.

Western Palearctic Water Frogs’ (&lt;i&gt;Pelophylax esculentus&lt;/i&gt; complex) Body Condition in Mixed Population Systems in Serbia Follow Levels of Habitat Suitability

Body condition is an important indicator in many ecological studies since it is expected that individuals and populations perform better in habitats more suitable for species. A wide range of metrics have been proposed as condition indices. In this study, we estimated the phenotypic condition of water frog species using the residual condition index. The study was carried out in three localities adjacent to nature preserves in South Banat, Serbia and with different levels of preserved natural features and anthropogenic pressure. Selected localities are typical habitats of water frogs with two parental and their hemiclonal hybrid species present. The localities were scored for suitability of the aquatic and terrestrial habitats. Statistical significance of residual condition index patterns from a multiway ANOVA was obtained for locality but not for species and sex. The lowest condition index was observed in frogs sampled from a locality maintained by human activity and with the lowest habitat suitability. Furthermore, the highest body condition index was obtained on the locality with the highest habitat suitability. One of the parental species, P. ridibundus had the highest overall body condition index while the hybrid species (P. esculentus) had the lowest. None of the three species from the complex had the highest body condition in all three localities, nor the worst.

Karyotypes of water frogs from the Pelophylax esculentus complex: results of cross-species chromosomal painting.

Amphibian species have the largest genome size enriched with repetitive sequences and relatively similar karyotypes. Moreover, many amphibian species frequently hybridize causing nuclear and mitochondrial genome introgressions. In addition, hybridization in some amphibian species may lead to clonality and polyploidization. All such events were found in water frogs from the genus Pelophylax. Among the species within the genus Pelophylax, P. esculentus complex is the most widely distributed and well-studied. This complex includes two parental species, P. ridibundus and P. lessonae, and their hybrids, P. esculentus, reproducing hemiclonally. Parental species and their hybrids have similar but slightly polymorphic karyotypes, so their precise identification is still required. Here, we have developed a complete set of 13 chromosome painting probes for two parental species allowing the precise identification of all chromosomes. Applying chromosomal painting, we identified homologous chromosomes in both parental species and orthologous chromosomes in their diploid hemiclonal hybrids. Comparative painting did not reveal interchromosomal exchanges between the studied water frog species and their hybrids. Using cross-specific chromosome painting, we detected unequal distribution of the signals along chromosomes suggesting the presence of species-specific tandem repeats. Application of chromosomal paints to the karyotypes of hybrids revealed differences in the intensity of staining for P. ridibundus and P. lessonae chromosomes. Thus, both parental genomes have a divergence in unique sequences. Obtained chromosome probes may serve as a powerful tool to unravel chromosomal evolution in phylogenetically related species, identify individual chromosomes in different cell types, and investigate the elimination of chromosomes in hybrid water frogs.

Functional and temporal facets of predation by marsh frogs across the aquatic–terrestrial ecotone of ponds and implications in the context of biological invasions

Abstract Freshwater vertebrate predators can exert trophic control over aquatic and littoral communities. Among these predators, post‐metamorphic anurans exhibit a biphasic trophic spectrum by foraging in both terrestrial and aquatic habitats. Many studies have described their diet through the classical taxonomic classification of prey. However, these singular diet habits imply a complex, time‐dependent, realised trophic niche in which predation pressure occurs over many consumers that fill diverse functional roles throughout the aquatic and terrestrial interface of ponds. Among anurans, marsh frogs (Pelophylax ridibundus) have been introduced outside their range in many countries and are now invading nationwide areas, particularly in western Europe. Focusing on their foraging specificities will therefore further the understanding of the trophic role of these alien taxa in pond environments that are highly colonised. We collected stomach contents from 761 marsh frogs from introduced populations in 19 ponds in southern France once a month over 4 months of their active period in the spring. The populations of marsh frogs were studied in a geographic area that was devoid of native water frogs and their origin tracks back as far as south‐eastern Europe (i.e., more than 1,000 km from the studied sites, as evidenced previously by genetic analyses). Marsh frogs exhibited generalist and opportunistic feeding strategies. The trophic niche was strongly asymmetrical and broader in the terrestrial environment than in the aquatic environment. However, predation occurred in communities of large freshwater macroinvertebrates and amphibians. Whereas the composition of the terrestrial diet exhibited strong seasonal variations, predation pressure was continuously exerted on the same aquatic organisms over time. Primary consumers and consumers at higher trophic levels frequenting aquatic benthic, vegetated, pelagic, and surface microhabitats were preyed upon, underlying the multidimensional extent of the predation spectrum. The diversified feeding strategies of alien marsh frogs highlight the extent of potential ecological control by predation on pond communities. Because of their wide trophic niche, they exert predation pressure on most pond organisms, triggering possible top‐down control of the overall aquatic communities. Our results show that the integration of the functional traits and microhabitats of consumed prey may aid in a better understanding of how predation by anurans may target specific components of pond communities. More particularly, this study raises concerns about the predatory role of introduced anurans in the context of biological invasions.

Species and hybrid composition and genetic diversity of water frogs (Pelophylax esculentus complex) in western Ukrainian hemiclonal population systems

Background. Two species of water frogs, Pelophylax ridibundus and Pelophylax lessonae, and their hybrid, Pelophylax kl. esculentus, are widespread in Ukraine. The purpose of this study was to investigate the population structure of various types of hemiclonal population systems (HPS) of water frogs formed due to the coexistence of frogs in the same territory. In Ukraine, a hybridization centre with the spread of triploid individuals of hybrid nature has been identified. Triploid hybrids are an intriguing research subject due to the diverse hypotheses about their origin and role in HPS. Outside the hybridization centre in Kharkiv Region, triploids are not commonly found. In our study, we describe the initial findings of triploid specimens in Lviv Region and analyze the genetic structure of the HPS where such individuals were detected. Methods. In total, 193 specimens of green frogs were collected between 2011 and 2015. Here we present population structure analysis which was conducted using two microsatellite loci, Rrid059A and RlCA1b5. A wide range of software programs were utilized for processing the genetic analysis data, including GenePop 4.7.5, Micro-Checker and NewHybrids 1.1. Results. Three types of hemiclonal population systems were identified: R-E type in Perekalky and Lake Pisochne, L-E type in Lake Luky, and R-E-L type in Nyzhankovychi, Velykyi Lyubin, Zhovtantsi and Cholgyni. Additionally, population systems with hybrids of mixed ploidy (diploids and triploids) were found in Perekalky, Velykyi Lyubin and Zhovtantsi. Conclusions. Genetic diversity analysis revealed variations in the number of alleles per population. P. ridibundus individuals exhibited higher genetic diversity compared to P. lessonae individuals, whereas hybrids showed intermediate genetic diversity. Further investigations of the localities where potential triploids were detected are necessary to assess the survival and reproductive potential of hybrid individuals and determine all types of hybrids and individuals of both marsh and pool frogs.

Skeletal taphonomy of the water frogs (Amphibia: Anura) from the Pit 7/8 of the Pliocene Camp dels Ninots site (Caldes de Malavella, NE Spain)

ABSTRACT The Pliocene lacustrine infill of Camp dels Ninots maar (Girona, Spain) hosts an exceptional record of complete articulated skeletons. Here we present the taphonomical description of 22 fossil water frogs recovered from the Pit 7/8 of Can Argilera Sector. Description of their skeletal taphonomy is done on the basis of their distribution, completeness, articulation and limb position, and by establishing comparisons with the late Miocene site of Libros (Spain). Microscopic examination shows no evidence of digestion and absence of weathering. Mass mortality or any environmental stress-induced factors cannot be ruled out, but natural death seems to be the most probable. Limited time of decay prior burial seems to be the main pattern explaining the relatively high degree of articulation and completeness. Floatation is not to be disregard for some more (proximally) disarticulated specimens. Taphonomical patterns document two types of sub-environments inside a cool and deep lake, suggesting a more complex depositional scenario for Camp dels Ninots than the ones described in others similar Konservat-Lagerstätten.