Pelodytes Punctatus Research Articles

The importance of naturalized quarries as amphibian breeding sites: a case study in central Spain

Naturalized quarries can host rich amphibian communities, potentially playing an important role in local and regional population dynamics. Despite their importance for conservation, few studies have evaluated their potential to host large, viable populations and to connect breeding nuclei in neighboring areas, promoting long-term demographic resilience at the regional scale. We used photo-identification as a capture-mark-recapture method to estimate the population sizes and dispersal patterns of two amphibians of regional conservation concern (Pleurodeles waltl and Pelodytes punctatus), which breed in temporary ponds in an abandoned, naturalized quarry in SE Madrid (central Spain). We also surveyed all water bodies potentially harboring amphibian populations in an 80 km2 area centered in our study site to detect additional breeding nuclei of the two species. Both species are abundant in the core study site, with estimated population sizes of around 300 individuals in P. waltl and about 800 in P. punctatus. We recorded 23 accumulated displacements, ranging from 80 to 840 m, performed by 20 individuals of P. waltl captured on multiple occasions, but were unable to detect spatial displacements of P. punctatus during the study. Regional surveys confirmed the presence of P. waltl and/or P. punctatus in 7 additional locations, mostly quarries, at distances of 0.6-4.4 km from the study site. Our results show that temporary ponds in naturalized quarries can represent key assets for the long-term resilience of amphibian populations in areas where human action has resulted in extensive habitat fragmentation and loss.

Global Warming and Long-Distance Spread of Invasive Discoglossus pictus (Amphibia, Alytidae): Conservation Implications for Protected Amphibians in the Iberian Peninsula

Discoglossus pictus is a North African amphibian that was introduced in southern France early the 20th century and has spread south and north along the Mediterranean coastal plains up to 170 km. In order to disentangle the conservation implications of the spread of D. pictus for sensitive native species, we examined the impact of long-term climate warming on the basis of niche overlap analysis, taking into account abiotic factors. The study area covered the distribution ranges of all genus Discoglossus species in northwestern Africa (659,784 km2), Sicily (27,711 km2), the Iberian Peninsula, and southern France (699,546 km2). Niche overlap was measured from species environmental spaces extracted via PCA, including climate and relief environmental variables. Current and future climatic suitability for each species was assessed in an ensemble-forecasting framework of species distribution models, built using contemporary species data and climate predictors and projected to 2070's climatic conditions. Our results show a strong climatic niche overlap between D. pictus and native and endemic species in the Iberian Peninsula. In this context, all species will experience an increase in climatic suitability over the next decades, with the only exception being Pelodytes punctatus, which could be negatively affected by synergies between global warming and cohabitation with D. pictus.

The role of habitat features in patterns of population connectivity of two Mediterranean amphibians in arid landscapes of central Iberia

ContextMediterranean wetland ecosystems are in continuous decline due to human pressure. Amphibians are key elements of biotic communities of Mediterranean temporary ponds and streams, and their persistence depends on the availability and inter-connectivity of breeding sites.ObjectivesWe investigated the role of different factors potentially driving functional connectivity patterns in two amphibian species at the landscape and local scales. We focused on two Mediterranean endemic pond-breeding amphibians inhabiting semi-arid landscapes of central Spain, the common parsley frog (Pelodytes punctatus) and the common midwife toad (Alytes obstetricans).MethodsWe genotyped 336 individuals of P. punctatus and 318 of A. obstetricans from 17 and 16 breeding populations at 10 and 17 microsatellite loci, respectively. We used remotely sensed vegetation/moisture indices and land use/cover data to derive optimized resistance surfaces and test their association with estimates of gene flow and migration rates across populations.ResultsWe found evidence for higher population connectivity in common midwife toads than in common parsley frogs, with a strong effect of water availability in patterns of population connectivity of both species. However, the two species differ in the role of landscape features on population connectivity, with the distance and spatial distribution of artificial land-use types positively influencing connectivity in A. obstetricans and meadows/pastureland favouring P. punctatus. This is in line with reported breeding site preferences for the two species, with A. obstetricans successfully breeding in artificial water bodies that P. punctatus generally avoid.ConclusionsThis study highlights the importance of assessing species–habitat relationships shaping connectivity when developing and implementing conservation and management actions to benefit fragmented amphibian populations in the Mediterranean region. Our results show that amphibian species respond differently, even contrastingly to landscape features and thus require alternative, complementary strategies to improve population connectivity and ensure long-term viability.

Bimodal breeding phenology in the Parsley Frog Pelodytes punctatus as a bet-hedging strategy in an unpredictable environment despite strong priority effects

Bimodal breeding phenology in the Parsley Frog Pelodytes punctatus as a bet-hedging strategy in an unpredictable environment despite strong priority effects

Spreading the risk of reproductive failure when the environment is unpredictable and ephemeral

A recommendation of: Helene Jourdan-Pineau, Pierre-Andre Crochet, Patrice David Bimodal breeding phenology in the Parsley Frog Pelodytes punctatus as a bet-hedging strategy in an unpredictable environment despite strong priority effects https://doi.org/10.1101/2022.02.24.481784

Breeding phenology of amphibians in a Mediterranean ephemeral stream (Ardèche, France)

We present the results of the monitoring of breeding phenology of an assemblage of eight species of amphibians in a Mediterranean ephemeral stream, located in the Ardèche department, France. For most species, during 11 consecutive years, phenology was rather constant from year to year, which is rather unusual in Mediterranean temporary ponds. The occurrence of summer breeding was not rare for three species: Pelobates cultripes (Cuvier, 1829), Pelodytes punctatus (Daudin, 1803) and Hyla meridionalis Böttger, 1874. Breeding occurrence is linked to rewetting events caused by active karst resurgences, fuelled by periods of intense rainfall episodes called “cévenol” episodes. We document for the first time a triannual breeding occurrence (spring, summer, and autumn), and an in situ record of a short tadpole development period, concerning particularly P. cultripes. The ecological factors which can explain this species richness and these unusual observations are outlined. In conclusion, we encourage the conservation and monitoring of amphibian communities in ephemeral streams, as the natural and scientific interests for this type of habitat are often underestimated.

Are Iberian ribbed newts Pleurodeles waltl Michahelles, 1830 negatively affecting the populations of other amphibians?

AbstractTemporary ponds play a key role as amphibian breeding habitats, but predation and desiccation risks enforce major evolutionary pressures in these ecosystems. The newt Pleurodeles waltl is commonly found in Mediterranean ponds in the Iberian Peninsula, where it preys on a wide variety of organisms. We hypothesize that P. waltl may negatively influence populations of coexisting amphibian larvae in the natural environment. To test it, we monitored the amphibian populations of 21 temporary ponds in Eastern Spain, 10 of which included P. waltl. We visited each pond fortnightly on nine occasions, estimating the abundance of adult P. waltl and tadpoles of each amphibian species present. We built zero‐inflated Generalized Linear Mixed Models (GLMMs) to test for the effects of pond area and adult and larval P. waltl abundance on tadpole abundance of all amphibian species present. Our results show significant negative effects of P. waltl abundances on the anurans Alytes obstetricans, Epidalea calamita, and Pelodytes punctatus. Species adapted to shorter hydroperiods such E. calamita and P. punctatus show lower densities in the presence of P. waltl larvae. A. obstetricans, with preference for longer hydroperiod ponds, seems to better thrive in sites where the newt is absent. This is the first field work suggesting a negative impact of P. waltl on coexisting anurans, even though more studies are needed to disentangle other negative effects related to unmeasured environmental variables or biotic interactions, which can be important according to the large variation encompassed by the random variables of site and sampling period in the mixed models.

Integration of molecular, bioacoustical and morphological data reveals two new cryptic species of Pelodytes (Anura, Pelodytidae) from the Iberian Peninsula.

Parsley frogs (Pelodytes) comprise the only genus in the family Pelodytidae, an ancient anuran lineage that split from their closest relatives over 140 million years ago. Pelodytes is a Palearctic group restricted to Western Eurasia including three extant species: the eastern species P. caucasicus, endemic to the Caucasus area, and two closely related species inhabiting Western Europe: the Iberian endemic P. ibericus and the more widespread P. punctatus. Previous studies based on mitochondrial and nuclear DNA markers have revealed the existence of two additional lineages of Parsley frogs in the Iberian Peninsula, which have been flagged as candidate species. Here, we integrate novel molecular, morphological and bioacoustical data to assess the differentiation of the four western Parsley frog lineages. Species trees and Bayesian population assignment analyses based on nuclear markers confirm previous studies and concordantly delineate four parapatric lineages with narrow hybrid zones. Mitochondrial divergence is low (< 2% pairwise distances in the 16S rRNA gene), in line with previously reported low mitochondrial substitution rates in non-neobatrachian frogs. Based on concordance between mitochondrial and nuclear markers, we conclude that four species of Parsley frogs occur in Western Europe: Pelodytes punctatus, distributed from northern Italy to northeastern Spain; Pelodytes ibericus, inhabiting southern Spain and southern Portugal; Pelodytes atlanticus sp. nov., from the Portuguese Atlantic coast; and Pelodytes hespericus sp. nov., occurring in central and eastern Spain. However, bioacoustical and morphological differentiation of these species is low, with no obvious and qualitative diagnostic characters allowing full species discrimination. Differences in the relative size of metacarpal tubercles exist but this character is variable. Pelodytes ibericus and Pelodytes atlanticus are smaller than the other two species, and P. ibericus has shorter limbs and various distinctive osteological characters. Bioacoustically, the pattern by which two different note types are combined in advertisement calls separates P. hespericus from the remaining species. Despite these differences, we emphasize that the taxonomic status of all four western Parsley frogs requires additional investigation, especially the patterns of genetic admixture across contact zones. While a status of separate species best conforms to the currently available data, alternative hypotheses are also discussed.

Middle to Late Pleistocene herpetofauna from Scladina and Sous-Saint-Paul caves (Namur, Belgium)

For the first time, the fossil herpetofauna from the Middle and Late Pleistocene of Scladina and Sous-Saint-Paul caves (Sclayn, Belgium) is described. The amphibians and squamate reptiles are represented by one salamander (Salamandra salamandra), three anurans (Pelodytes punctatus, Bufo bufo and Rana temporaria), two lizards (Lacerta cf. agilis and Anguis fragilis) and two snakes (Zamenis longissimus and Vipera cf. berus). The occurrence of the Parsley Frog (Pelodytes punctatus) and the Aesculapian Snake (Zamenis longissimus), which are not currently represented in Belgium, is of particular interest. Scladina also represents one of the northernmost fossil mentions for the Fire Salamander (Salamandra salamandra) although it is within its current distribution in Europe. Finally, the presence of the Adder (Vipera cf. berus) is very probably attested in Scladina whereas today this snake is infrequent and classified as endangered in Belgium.

Within-Population Developmental and Morphological Plasticity is Mirrored in Between-Population Differences: Linking Plasticity and Diversity

It has been suggested that phenotypic plasticity can facilitate evolutionary diversification of organisms. If life-history and morphological diversification across a lineage is mirrored in diversification in the same traits due to phenotypic plasticity within a lineage it fulfils one of the expectations that are needed to support this diversification hypothesis. We carried out a laboratory study to examine development rate and morphology between and within populations of the parsley frog, Pelodytes punctatus. We found that frogs reared in the laboratory had a longer development time, relatively longer hind legs and relatively narrower heads under constant water level compared to those under decreasing water level simulating pool drying. This adaptive phenotypic plasticity response to pool drying was mirrored across populations because frogs from permanent waters had longer development times, relatively longer hind legs and relatively narrower heads compared to frogs from temporary waters. Hence the developmental and morphological plasticity observed within populations was also observed between populations as constitutive expressed traits. We suggest that the morphology pattern observed was driven by a common developmental process (time to metamorphosis), indicating that plasticity may contribute to evolutionary change, ultimately resulting in genetic accommodation of the morphological traits.

The origin of modern frogs (Neobatrachia) was accompanied by acceleration in mitochondrial and nuclear substitution rates

BackgroundUnderstanding the causes underlying heterogeneity of molecular evolutionary rates among lineages is a long-standing and central question in evolutionary biology. Although several earlier studies showed that modern frogs (Neobatrachia) experienced an acceleration of mitochondrial gene substitution rates compared to non-neobatrachian relatives, no further characterization of this phenomenon was attempted. To gain new insights on this topic, we sequenced the complete mitochondrial genomes and nine nuclear loci of one pelobatoid (Pelodytes punctatus) and five neobatrachians, Heleophryne regis (Heleophrynidae), Lechriodus melanopyga (Limnodynastidae), Calyptocephalella gayi (Calyptocephalellidae), Telmatobius bolivianus (Ceratophryidae), and Sooglossus thomasseti (Sooglossidae). These represent major clades not included in previous mitogenomic analyses, and most of them are remarkably species-poor compared to other neobatrachians.ResultsWe reconstructed a fully resolved and robust phylogeny of extant frogs based on the new mitochondrial and nuclear sequence data, and dated major cladogenetic events. The reconstructed tree recovered Heleophryne as sister group to all other neobatrachians, the Australasian Lechriodus and the South American Calyptocephalella formed a clade that was the sister group to Nobleobatrachia, and the Seychellois Sooglossus was recovered as the sister group of Ranoides. We used relative-rate tests and direct comparison of branch lengths from mitochondrial and nuclear-based trees to demonstrate that both mitochondrial and nuclear evolutionary rates are significantly higher in all neobatrachians compared to their non-neobatrachian relatives, and that such rate acceleration started at the origin of Neobatrachia.ConclusionsThrough the analysis of the selection coefficient (ω) in different branches of the tree, we found compelling evidence of relaxation of purifying selection in neobatrachians, which could (at least in part) explain the observed higher mitochondrial and nuclear substitution rates in this clade. Our analyses allowed us to discard that changes in substitution rates could be correlated with increased mitochondrial genome rearrangement or diversification rates observed in different lineages of neobatrachians.

Reproductive dynamics of three amphibian species in Mediterranean wetlands: the role of local precipitation and hydrological regimes

Summary1. Although the influence of water availability and precipitation regimes on amphibians has been studied at large scales, whether and how interannual rainfall and hydrological variations affect amphibians dynamics at a local scale have rarely been addressed. In this respect, accounting for variations in species detectability in space and time has also been overlooked.2. We assessed the effects of rainfall and hydrological variations on the breeding dynamics of three amphibian taxa: Pelodytes punctatus, Hyla meridionalis and Pelophylax spp. in 20 ponds of the Camargue region (southern France) over a 7‐year study period.3. We used multiple season occupancy models to test the effect of winter–spring rainfall and interannual variations in hydroperiod, mean water depth and drought events on tadpole presence in spring (March–June), a proxy for breeding dynamics.4. We used an independent survey with spatial replicates (dipnet sweeps) to disentangle the relative contributions of phenology and detectability to the absence of records in a given month. For the three taxa considered, the probability of missing a species when that species was actually present in a pond was most often negligible. Hence, we could consider that multiseason models properly tracked changes in species phenology.5. Pelodytes punctatus was first detected in March, while the two other taxa appeared later in April. Hyla meridionalis appeared as a mid‐season species with much more synchronous pond occupancy than Pelodytes punctatus. The detection peak of Pelophylax spp. was short and unexpectedly early for this taxon.6. Seasonal winter–spring rainfall was associated with a decrease in extinction rates and even more strongly with an increase in colonisation rates at individual ponds.7. Colonisation rate increased following an annual drought and was best modelled as a negative quadratic effect of the variance of pond hydroperiod. Extinction probability was best modelled by a negative quadratic effect of mean water level. Hence, breeding was more stochastic (i) in unpredictable and shallow ponds because of yearly drying up and (ii) in highly predictable and deep ponds, possibly due to the presence of predators such as fish and crayfish.8. Overall, we show that ponds with intermediate rather than extreme variations in environmental conditions currently correspond to optimal breeding sites. Our study demonstrates that amphibian monitoring coupled with fine‐scale analysis of environmental conditions is necessary to understand species dynamics in the long run and to inform conservation efforts for these species.

Effects of the non-native amphibian species Discoglossus pictus on the recipient amphibian community: niche overlap, competition and community organization

The painted frog, Discoglossus pictus, was introduced into the Iberian Peninsula 100 years ago and its distribution has steadily increased since then. We studied the effects of this non-native amphibian species on the native ones in the northeastern area of the peninsula. We compared amphibian assemblages in regions with and without D. pictus to estimate niche overlap between species. Additionally, we carried out a laboratory evaluation of the effects of competition between the non-native and the two native species with which it overlaps most commonly: Bufo calamita and Pelodytes punctatus. The presence of D. pictus larvae reduced the survival, body mass and activity of B. calamita, and increased time to metamorphosis. Furthermore, D. pictus showed the highest consumption rate while P. punctatus showed the lowest. One possible consequence of these competitive interactions is an alteration of species co-occurrence patterns in the recipient community on a regional scale. In the non-invaded area, the checkerboard score (C-score) of co-occurrence indicated that the community was structured, whereas the standardized C-score in the invaded area indicated that the community did not differ significantly from having a random structure. These results suggest that competition between native and non-native species can cause recipient communities to become less structured.

TESTING THE INFLUENCE OF FAMILY STRUCTURE AND OUTBREEDING DEPRESSION ON HETEROZYGOSITY-FITNESS CORRELATIONS IN SMALL POPULATIONS

Theory predicts that positive heterozygosity-fitness correlations (HFCs) arise as a consequence of inbreeding, which is often assumed to have a strong impact in small, fragmented populations. Yet according to empirical data, HFC in such populations seem highly variable and unpredictable. We here discuss two overlooked phenomena that may contribute to this variation. First, in a small population, each generation may consist of a few families. This generates random correlations between particular alleles and fitness (AFCs, allele-fitness correlations) and results in too liberal tests for HFC. Second, in some contexts, small populations receiving immigrants may be more impacted by outbreeding depression than by inbreeding depression, resulting in negative rather than positive HFC. We investigated these processes through a case study in tadpole cohorts of Pelodytes punctatus living in small ponds. We provide evidence for a strong family structure and significant AFC in this system, as well as an example of negative HFC. By simulations, we show that this negative HFC cannot be a spurious effect of family structure, and therefore reflects outbreeding depression in the studied population. Our example suggests that a detailed examination of AFC and HFC patterns can provide valuable insights into the internal genetic structure and sources of fitness variation in small populations.

How does the invasive/native nature of species influence tadpoles’ plastic responses to predators?

SynthesisAnti–predator phenotypic plasticity is expected to be one of the major ecological forces driving survival and rapid evolution of prey facing new predators. This implies that biological invasions embody a perfect case for studying the tradeoffs and evolution of phenotypic plasticity. Our manuscript reports on high prey–predator specificity in these reactions and an evolutionary dissociation between behavioral and morphological plasticity in anurans. Each species displayed a particular set of tradeoffs between plastic responses and their costs, but interestingly we also detected mild patterns in combinations using introduced predators. Given the speed at which these evolutionary changes become noticeable and their potential in reducing predation risk, the role of antipredator phenotypic plasticity is expected to be crucial for population dynamics during biological invasions.Although the purely ecological impacts of biological invasions have been well studied, a less thorough effort has been made in terms of their evolutionary ecology. Previous studies show that anti‐predator phenotypic plasticity may be one of the major ecological forces driving survival and rapid evolution of prey facing new predators. In turn, this means that biological invasions embody a perfect case for studying the tradeoffs and evolution of phenotypic plasticity per se. Here, we studied the plastic responses of native (Pelodytes punctatus) and invasive (Discoglossus pictus) anurans facing a native (dragonfly Anax sp.) and two invasive (fish Gambusia holbrooki and crayfish Procambarus clarkii) predators. Marked responses were reported against the native predator from both the native and the invasive anuran, but they both responded mildly to the exotic predators as well. Native P. punctatus displayed a morphological reaction to invasive P. clarkii after scarcely 30 years of coexistence with this predatory crayfish and responded behaviorally to the invasive fish G. holbrooki. Invasive D. pictus reacted behaviorally to all predators, but unexpectedly only reacted morphologically to native Anax sp. All these results support high prey–predator specificity in these reactions and an evolutionary dissociation between behavioral and morphological plasticity in anurans. Each species displayed a particular set of tradeoffs between plastic responses and their costs, which is probably due to differences in ecological niche and evolutionary history, but interestingly we usually detected unexpected patterns in combinations using introduced predators. This suggests that perhaps singular plastic shifts usually occur when tadpoles face recently introduced species. Given the speed in which these evolutionary changes become noticeable and their potential in avoiding predation risk, this study supports that phenotypic plasticity might play an important role in population dynamics during biological invasions.

Phenotypic plasticity allows the Mediterranean parsley frog Pelodytes punctatus to exploit two temporal niches under continuous gene flow

Environmental changes, such as climate change, lead to the opening of new niches. In such situations, species that adapt to new niches can survive and/or expand their ranges. However, gene flow can hamper genetic adaptation to new environments. Alternatively, recent models have highlighted the importance of phenotypic plasticity in tracking environmental change. Here, we investigate whether phenotypic plasticity or genetic evolution (or both) allows an amphibian species to exploit two divergent climatic niches. In the Mediterranean region, the parsley frog Pelodytes punctatus breeds both in spring, as do most other species, and in autumn, a temporal niche not exploited by most other species, but which may become increasingly important with global warming. Conditions of development are dramatically different between the two seasons and deeply impact tadpole life-history traits. To determine whether these temporal niches are exploited by two genetically differentiated subpopulations, or whether the bimodal phenology arises in a panmictic population displaying plastic life-history traits, we use two complementary approaches. We measure both molecular genetic differentiation and quantitative-trait differentiation between spring and autumn cohorts, using microsatellites and common garden experiments, respectively. Seasonal cohorts were not genetically differentiated and differences in tadpole life history between cohorts were not maintained in laboratory conditions. We conclude that phenotypic plasticity, rather than genetic adaptation, allows Parsley frog to exploit two contrasting temporal niches.

Genetic evidence for a distinct Pelodytes lineage in southwest Portugal: implications for the use of pre-developed microsatellite markers

For population genetic analyses of Parsley frogs in Iberia we initially used microsatellite markers previously developed for Pelodytes punctatus in southwest Portugal. However, several loci indicated a strong signal of amplification failure for individuals from northern Spain. Cryptic species or genetic entities are suspected to occur in southwest Portugal on the basis of studies with other species and understanding cryptic diversity is a concern as amphibian habitat, temporary ponds in traditional Mediterranean farmland, is disappearing at a fast rate. Our study revealed a new Pelodytes lineage in southwest Portugal which appears to be discrete. However, the rare occurrence of a distinct mitochondrial haplotype from its sister species, despite no nuclear differentiation, is a signature of introgression indicating that reproductive isolation is not complete.

Assessing the potential impact of an invasive species on a Mediterranean amphibian assemblage: a morphological and ecological approach

The introduction of exotic species is a major cause of ecological disturbance and has recently been shown to promote the decline of some amphibian populations. In Western Europe, several amphibian species have been introduced in recent decades, among them Discoglossus pictus, impact of which in native amphibian communities is still unknown. We studied the potential impact of D. pictus by analysing the degree of niche overlap, assuming the possible existence of competitive interactions with native species. We have studied the structure of the anuran assemblage at local level, defining the morphospace occupied by native species and the habitat occupied by the different ecomorphs. The analysis of distance matrices suggested that there was a covariation between morphological characters and habitat selection. We determined the position of D. pictus within the morphospace of the native anuran community, patterns of co-occurrence among alien, and native species and habitat selection. The potential effect of climate on local assemblages had been controlled based on data obtained from climate models. These analysis showed that D. pictus was clustered with the benthic guild, selected positively small ephemeral ponds and was a thermophilic species. Based on these results, a greater degree of niche overlap was expected with Bufo calamita and Pelodytes punctatus. The definition of morphological groups can be useful to understand the invaded assemblage structure and the potential effect of an alien frog on native communities.

Chondrocranial ontogeny of Pelodytes punctatus (Anura: Pelodytidae). Response to competition: geometric morphometric and allometric change analysis

AbstractGarriga, N. and Llorente, G.A. 2011. Chondrocranial Ontogeny of Pelodytes punctatus (Anura: Pelodytidae). Response to competition: Geometric Morphometric and Allometric Change Analysis. —Acta Zoologica (Stockholm) 93: 453–464.The chondrocranial development of Pelodytes punctatus is described, from tadpole to froglet, and compared with that of other taxa reported previously, such as species in the Pelobatidae, Pipidae, Ranidae, Hylidae, Bombinatoridae, Leptodactylidae, or Microhylidae families. The comparison leads us to suggest that the ontogeny of the anuran chondrocranium is very conservative, making it difficult to discern phylogenetic or ecologic patterns. Chondrocranial development is also analyzed to quantify shape changes and allometries during ontogeny, using linear and geometric morphometrics. The main shape change observed follows the general pattern of vertebrate postnatal development. The allometric analysis indicates the presence of different functional units in the chondrocranium that could be subjected to different pressures. Finally, tadpoles were raised in two conditions of competition to compare their chondrocranium development. The largest shape differences between the two conditions are located in the anterior region of the cranium and fit the general response to competition stress by increasing growth rate. Comparison of the scaling pattern between Pelodytes and Rana sylvatica and Bufo americanus shows differences, principally in the oral region, that do not fit with the general allometric pattern in larval anurans proposed in previous studies.

A very diverse amphibian and reptile assemblage from the late Middle Pleistocene of the Sierra de Atapuerca (Sima del Elefante, Burgos, Northwestern Spain)

Among the Pleistocene localities of the Sierra de Atapuerca, the site called Sima del Elefante is famous for having delivered in its lower level (TE-LRU) some hominid remains currently considered the oldest in Western Europe (about 1.2 Ma). In its upper part (TE-URU), this site has fossiliferous levels pertaining to the late Middle Pleistocene (350-250 ka). Here we describe for the first time the amphibians and reptiles of these upper levels (TE18 and TE19), which have proved to be one of the richest assemblages of all the localities of the Sierra de Atapuerca. The faunal list is composed of 18 taxa made up of urodeles ( Salamandra salamandra and Lissotriton helveticus), anurans ( Discoglossus sp., Alytes sp. Pelobates cultripes, Pelodytes punctatus, Bufo bufo, Bufo calamita, Hyla arborea and cf. Rana sp.), a terrestrial tortoise ( Testudo s.l.), lizards ( Lacerta s.l., Podarcis sp. and Anguis fragilis) and snakes ( Natrix natrix, Natrix maura, Coronella cf. girondica and Vipera latasti). For the first time, the genera Lissotriton, Discoglossus and Podarcis are mentioned in the Pleistocene localities of the Sierra de Atapuerca. TE19 also corresponds to the earliest mention for L. helveticus in the Iberian Peninsula. With the exception of tortoises, all these species are currently present in the province of Burgos, and thus suggests that the herpetofauna has a modern aspect since the Middle Pleistocene. This association of amphibians and reptiles suggests a slightly warmer climate than the current one, but may correspond to a “cold and dry” period if compared with other Pleistocene localities of the Sierra de Atapuerca. The landscape was probably composed of a gallery forest along a quiet water river within a Mediterranean environment alternating laterally between dry meadows, rocky or stony areas and open scrubland.