A novel tamanavirus (Flaviviridae) of the European common frog (Rana temporaria) from the UK.

Flavivirids are small, enveloped, positive-sense RNA viruses from the family Flaviviridae with genomes of ~9-13 kb. Metatranscriptomic analyses of metazoan organisms have revealed a diversity of flavivirus-like or flavivirid viral sequences in fish and marine invertebrate groups. However, no flavivirus-like virus has been identified in amphibians. To remedy this, we investigated the virome of the European common frog (Rana temporaria) in the UK, utilizing high-throughput sequencing at six catch locations. De novo assembly revealed a coding-complete virus contig of a novel flavivirid ~11.2 kb in length. The virus encodes a single ORF of 3456 aa and 5' and 3' untranslated regions (UTRs) of 227 and 666 nt, respectively. We named this virus Rana tamanavirus (RaTV), as BLASTp analysis of the polyprotein showed the closest relationships to Tamana bat virus (TABV) and Cyclopterus lumpus virus from Pteronotus parnellii and Cyclopterus lumpus, respectively. Phylogenetic analysis of the RaTV polyprotein compared to Flavivirus and Flavivirus-like members indicated that RaTV was sufficiently divergent and basal to the vertebrate Tamanavirus clade. In addition to the Mitcham strain, partial but divergent RaTV, sharing 95.64-97.39 % pairwise nucleotide identity, were also obtained from the Poole and Deal samples, indicating that RaTV is widespread in UK frog samples. Bioinformatic analyses of predicted secondary structures in the 3'UTR of RaTV showed the presence of an exoribonuclease-resistant RNA (xrRNA) structure standard in flaviviruses and TABV. To examine this biochemically, we conducted an in vitro Xrn1 digestion assay showing that RaTV probably forms a functional Xrn1-resistant xrRNA.

Differentiation of Central Slovenian and Moscow populations of Rana temporaria frogs using peptide biomarkers of temporins family.

Skin secretion represents the only means of defense for the majority of frog species. That phenomenon is based on the fact that the main components of the secretion are peptides demonstrating greatly varying types of bioactivity. They fulfill regulatory functions, fight microorganisms and may be even helpful against predators. These peptides are considered to be rather promising pharmaceuticals of future generation as according to the present knowledge microorganisms are unlikely to develop resistance to them. Mass spectrometry sequencing of these peptides is the most efficient first step of their study providing reliably their primary structures, i.e., amino acids sequence and S-S bond motif. Besides discovering new bioactive peptides, mass spectrometry appears to be an efficient tool of taxonomy studies, allowing for distinguishing not only between closely related species, but also between populations of the same species. Application of several tandem mass spectrometry tools (CID, HCD, ETD, EThcD) available with Orbitrap mass analyzer allowed us to obtain full sequence of about 60 peptides in the secretion of Slovenian population of brown ranid frog Rana temporaria. The problem of sequence inside C-terminal cycle formed by two Cys and differentiation of isomeric Leu and Ile residues was done in top-down mode without any derivatization steps. Besides general biomarkers of Rana temporaria species, Central Slovenian population of Rana temporaria demonstrates six novel temporins and one brevinin 1, which may be treated as biomarkers of that population.

Are glacial refugia hotspots of speciation and cytonuclear discordances? Answers from the genomic phylogeography of Spanish common frogs.

Subdivided Pleistocene glacial refugia, best known as "refugia within refugia", provided opportunities for diverging populations to evolve into incipient species and/or to hybridize and merge following range shifts tracking the climatic fluctuations, potentially promoting extensive cytonuclear discordances and "ghost" mtDNA lineages. Here, we tested which of these opposing evolutionary outcomes prevails in northern Iberian areas hosting multiple historical refugia of common frogs (Rana cf. temporaria), based on a genomic phylogeography approach (mtDNA barcoding and RAD-sequencing). We found evidence for both incipient speciation events and massive cytonuclear discordances. On the one hand, populations from northwestern Spain (Galicia and Asturias, assigned to the regional endemic R. parvipalmata), are deeply-diverged at mitochondrial and nuclear genomes (~4 My of independent evolution), and barely admix with northeastern populations (assigned to R. temporaria sensu stricto) across a narrow hybrid zone (~25 km) located in the Cantabrian Mountains, suggesting that they represent distinct species. On the other hand, the most divergent mtDNA clade, widespread in Cantabria and the Basque country, shares its nuclear genome with other R. temporaria s. s. lineages. Patterns of population expansions and isolation-by-distance among these populations are consistent with past mitochondrial capture and/or drift in generating and maintaining this ghost mitochondrial lineage. This remarkable case study emphasizes the complex evolutionary history that shaped the present genetic diversity of refugial populations, and stresses the need to revisit their phylogeography by genomic approaches, in order to make informed taxonomic inferences.

No evidence that Y-chromosome differentiation affects male fitness in a Swiss population of common frogs.

The canonical model of sex-chromosome evolution assigns a key role to sexually antagonistic (SA) genes on the arrest of recombination and ensuing degeneration of Y chromosomes. This assumption cannot be tested in organisms with highly differentiated sex chromosomes, such as mammals or birds, owing to the lack of polymorphism. Fixation of SA alleles, furthermore, might be the consequence rather than the cause of recombination arrest. Here we focus on a population of common frogs (Rana temporaria) where XY males with genetically differentiated Y chromosomes (nonrecombinant Y haplotypes) coexist with both XY° males with proto-Y chromosomes (only differentiated from X chromosomes in the immediate vicinity of the candidate sex-determining locus Dmrt1) and XX males with undifferentiated sex chromosomes (genetically identical to XX females). Our study finds no effect of sex-chromosome differentiation on male phenotype, mating success or fathering success. Our conclusions rejoin genomic studies that found no differences in gene expression between XY, XY° and XX males. Sexual dimorphism in common frogs might result more from the differential expression of autosomal genes than from sex-linked SA genes. Among-male variance in sex-chromosome differentiation seems better explained by a polymorphism in the penetrance of alleles at the sex locus, resulting in variable levels of sex reversal (and thus of X-Y recombination in XY females), independent of sex-linked SA genes.

Actin depolymerization disrupts karyosphere capsule integrity but not residual transcription in late oocytes of the grass frog Rana temporaria.

Late diplotene oocytes are characterized by an essential decrease in transcriptional activity. At this time, chromosomes condense and form a compact structure named a karyosphere. The karyosphere of grass frogs Rana temporaria is surrounded by a fibrillar karyosphere capsule (KC). One of the main protein constituents of R. temporaria KC is actin. In this study, we used antibodies against different actin epitopes to trace different forms of actin in the KC. We also investigated the effect of F-actin depolymerization on the oocyte nuclear structures and transcription of chromatin DNA and rDNA in the amplified nucleoli. It was determined that disruption of actin filaments leads to chromosome shrinkage, nucleoli fusion, and distortion of the KC structure, but does not inhibit residual transcription in both the karyosphere and the nucleoli.

Effects of historic and projected climate change on the range and impacts of an emerging wildlife disease.

The global trend of increasing environmental temperatures is often predicted to result in more severe disease epidemics. However, unambiguous evidence that temperature is a driver of epidemics is largely lacking, because it is demanding to demonstrate its role among the complex interactions between hosts, pathogens, and their shared environment. Here, we apply a three-pronged approach to understand the effects of temperature on ranavirus epidemics in UK common frogs, combining in vitro, in vivo, and field studies. Each approach suggests that higher temperatures drive increasing severity of epidemics. In wild populations, ranavirosis incidents were more frequent and more severe at higher temperatures, and their frequency increased through a period of historic warming in the 1990s. Laboratory experiments using cell culture and whole animal models showed that higher temperature increased ranavirus propagation, disease incidence, and mortality rate. These results, combined with climate projections, predict severe ranavirosis outbreaks will occur over wider areas and an extended season, possibly affecting larval recruitment. Since ranaviruses affect a variety of ectothermic hosts (amphibians, reptiles, and fish), wider ecological damage could occur. Our three complementary lines of evidence present a clear case for direct environmental modulation of these epidemics and suggest management options to protect species from disease.

Effect-based environmental monitoring for thyroid disruption in Swedish amphibian tadpoles.

It is well-known that the metamorphosis process in amphibians is dependent on thyroid hormones. Laboratory studies have shown that several environmental contaminants can affect the function of thyroid hormones leading to alterations in the amphibian metamorphosis. The basic idea of the present study was to elucidate if the amphibian metamorphosis might be a useful tool as biomarker for effect-based environmental monitoring, examining wild tadpoles for potential thyroid hormone disruption. A laboratory test was performed to identify the responses from exposure to 6-propylthiouracil (PTU), which has a well-known mechanism on the thyroid system, on Swedish tadpoles from the Rana genus. This was followed by an environmental monitoring study where tadpoles of Rana arvalis, R. temporaria, and Bufo bufo were sampled from various sites in Sweden. Morphological data such as body weight, histopathological measurements of the thyroid glands, and environmental parameters were recorded. The results revealed that Rana tadpoles respond similar as other amphibians to PTU exposure, with interrupted development and increased size relative to the developmental stage. Data on some wild tadpoles showed similar features as the PTU exposed, such as high body weight, thus suggesting potential thyroid disrupting effects. However, histological evaluation of thyroid glands and pesticide analyses of the water revealed no clear evidence of chemical interactions. To a minor degree, the changes in body weight may be explained by natural circumstances such as pH, forest cover, and temperature. The present study cannot fully explain whether the high body weights recorded in some tadpoles have natural or chemical explanations. However, the study reveals that it is clearly achievable to catch tadpoles in suitable stages for the use in this type of biomonitoring and that the use of these biomarkers for assessment of thyroid disruption seems to be highly relevant.

Deciphering the drivers of negative species-genetic diversity correlation in Alpine amphibians.

The evolutionary and ecological importance of neutral and adaptive genetic diversity is widely recognized. Nevertheless, genetic diversity is rarely assessed for conservation planning, which often implicitly assumes a positive correlation between species and genetic diversity. Multiple drivers can cause the co-variation between the genetic diversity of one species and the richness of the whole communities, and explicit tests are needed to identify the processes that can determine species-genetic diversity correlations (SGDCs). Here, we tested whether intrapopulation genetic diversity (at neutral loci) and species richness co-vary in the amphibian communities of a southern Alpine region (Trentino, Italy), using the common frog (Rana temporaria) as focal species for the study of genetic diversity. We also analysed ecological similarity, niche overlap and interspecific interactions between the species, to unravel the processes determining SGDC. The neutral genetic diversity of common frogs was negatively related to species richness. The negative SGDC was probably due to an opposite influence of environmental gradients on the two levels of biodiversity, since the focal species and the other amphibians differ in ecological preferences, particularly in terms of thermal optimum. Conversely, we did not find evidence for a role of interspecific interactions in the negative SGDC. Our findings stress that species richness cannot be used as a universal proxy for genetic diversity, and only combining SGDC with analyses on the determinants of biodiversity can allow to identify the processes determining the relationships between genetic and species diversity.

A matter of proportion? Associational effects in larval anuran communities under fish predation.

In Batesian mimicry, a species lacking defences against predators benefits from mimicking the aposematic signal of a defended species, while the model may incur the costs of reduced defensive efficacy. Similar reciprocal indirect effects may emerge even when the signal is not mimicked; termed associational effects, such interactions are well known in plants sharing herbivores but have received little attention in animal studies. We investigated associational interactions in a system where unequally defended prey (chemically defended Bufo bufo and undefended Rana temporaria tadpoles), sharing general morphology but not an aposematic signal, were exposed to predation by the carp Cyprinus carpio along a gradient of relative prey abundance. In the absence of fish, the assemblage composition had no effect on the survival of Rana, while that of Bufo decreased with increasing abundance of Rana. Fish reduced the survival of tadpoles from both species. However, increased relative abundance of Bufo in the community led to enhanced survival in both Bufo and Rana. Increasing relative proportions of heterospecifics reduced metamorph mass only in Bufo, indicating greater sensitivity to interspecific competition compared to Rana; the effect was reduced in the presence of fish. Our results show that undefended non-mimetic prey enjoy reduced predation with increasing relative abundance of chemically defended prey, which in turn suffer greater mortality with an increasing proportion of the undefended species. Associational resistance/susceptibility, driven by current assemblage composition, not by selection for resemblance, can shape the dynamics of mixed communities of defended and undefended prey in the absence of mimicry.

Herpesvirus skin disease in free-living common frogs Rana temporaria in Great Britain.

Infectious disease is a significant driver of global amphibian declines, yet despite this, relatively little is known about the range of pathogens that affect free-living amphibians. Recent detection of the tentatively named Ranid herpesvirus 3 (RHV3), associated with skin disease in free-living common frogs Rana temporaria in Switzerland, helps to address this paucity in knowledge, but the geographic distribution and epidemiology of the pathogen remains unclear. Syndromic surveillance for ranid herpesvirus skin disease was undertaken throughout Great Britain (GB), January 2014 to December 2016. Reports of common frogs with macroscopic skin lesions with a characteristic grey appearance were solicited from members of the public. Post-mortem examination was conducted on one affected frog found dead in 2015 at a site in England. In addition, archived samples from an incident involving common frogs in England in 1997 with similar macroscopic lesions were further investigated. Transmission electron microscopy identified herpes-like virions in skin lesions from both the 1997 and 2015 incidents. RHV3, or RHV3-like virus, was detected in skin lesions from the 2015 case by PCR and sequencing. Our findings indicate that herpesvirus skin disease is endemic in common frogs in GB, with widespread distribution at apparently low prevalence. Further research into the role of host immunity, virus latency and the significance of infection to host survival is required to better understand the epidemiology and impact of cutaneous herpesvirus infections in amphibian populations.

Isoprenaline Impairs Contractile Function of Ventricular Myocardium in Common Frog (Rana temporaria).

The contractile function of the heart was studied in adult frogs Rana temporaria under the influence of a toxic dose of isoprenaline under conditions of natural sinoatrial rhythm and during heart pacing. The dynamics of ventricular pressure was recorded with a Prucka MacLab 2000 instrument via a catheter introduced into the ventricle through the ventricular wall. Reduced (p<0.05) parameters of the pump function (HR, maximum ventricular systolic pressure, isovolumic indices dP/dtmax and dP/dtmin) and lengthening of QRS complex and QT interval on ECG attested to impairment of contractile function and electrical processes after exposure to isoprenaline. Electrical stimulation of the right atrium improved myocardial contractility and ECG parameters after the administration of isoprenaline.

Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North.

Endothermic organisms can adapt to short growing seasons, low temperatures and nutrient limitation by developing high growth rates and high gross growth efficiencies (GGEs). Animals with high GGEs are better at assimilating limiting nutrients and thus should recycle (or lose) fewer nutrients. Longer guts in relation to body mass may facilitate higher GGE under resource limitation. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations in GGE, mediated by gut length, to its ecosystem consequences, such as consumer-mediated nutrient recycling. In common garden experiments, we raised Rana temporaria tadpoles from two regions (Arctic/Boreal) under two temperature regimes (18/23 °C) crossed with two food quality treatments (high/low-nitrogen content). We measured tadpole GGEs, total nutrient loss (excretion + egestion) rates and gut length during ontogeny. In order to maintain their elemental balance, tadpoles fed low-nitrogen (N) food had lower N excretion rates and higher total phosphorous (P) loss rates than tadpoles fed high-quality food. In accordance with expectations, Arctic tadpoles had higher GGEs and lower N loss rates than their low-latitude conspecifics, especially when fed low-N food, but only in ambient temperature treatments. Arctic tadpoles also had relatively longer guts than Boreal tadpoles during early development. That temperature and food quality interacted with tadpole region of origin in affecting tadpole GGEs, nutrient loss rates and relative gut length, suggests evolved adaptation to temperature and resource differences. With future climate change, mean annual temperatures will increase. Additionally, species and genotypes will migrate north. This will change the functioning of Boreal and Arctic ecosystems by affecting consumer-mediated nutrient recycling and thus affect nutrient dynamics in general. Our study shows that evolved latitudinal adaption can change key ecosystem functions.

Behavioural adaptations of Rana temporaria to cold climates.

Environmental conditions at the edge of a species' ecological optimum can exert great ecological or evolutionary pressure at local populations. For ectotherms like amphibians temperature is one of the most important abiotic factors of their environment as it influences directly their metabolism and sets limits to their distribution. Amphibians have evolved three ways to cope with sub-zero temperatures: freeze tolerance, freeze protection, freeze avoidance. The aim of this study was to assess which strategy common frogs at mid and high elevation use to survive and thrive in cold climates. In particular we (1) tested for the presence of physiological freeze protection, (2) evaluated autumnal activity and overwintering behaviour with respect to freeze avoidance and (3) assessed the importance of different high-elevation microhabitats for behavioural thermoregulation. Common frogs did not exhibit any signs of freeze protection when experiencing temperatures around 0 °C. Instead they retreated to open water for protection and overwintering. High elevation common frogs remained active for around the same period of time than their conspecifics at lower elevation. Our results suggest that at mid and high elevation common frogs use freeze avoidance alone to survive temperatures below 0 °C. The availability of warm microhabitats, such as rock or pasture, provides high elevation frogs with the opportunity of behavioural thermoregulation and thus allows them to remain active at temperatures at which common frogs at lower elevation cease activity.

Influences of ski-runs, meadow management and climate on the occupancy of reptiles and amphibians in a high-altitude environment of Italy.

Alpine ecosystems harbour a rich and highly specialised biodiversity, which is particularly susceptible to anthropogenic disturbances such as habitat loss and fragmentation as well as to climate change. Combined with other forms of land-use conversion, construction and maintenance of ski resorts can have severe consequences on alpine biodiversity. In this study, we show how one amphibian and two reptile species, namely Rana temporaria, Zootoca vivipara and Vipera berus, respond to such impacts by means of a multi-season occupancy analysis. We found all three species both in and outside ski-runs, showing that these habitats do not necessarily preclude their occurrence. Contrarily, this is influenced more by microhabitat availability, such as ground vegetation, humid areas and rock cover, rather than by macro-characteristics like elevation or habitat type. Moreover, we found a climatic influence on the year-to-year occupancy change of the species, with activity-month conditions being more relevant than overwintering ones. Our results demonstrate how, in the specific case of reptiles and amphibians, ski resorts do not necessarily limit species' occurrence and that a mild series of management actions might secure the species' persistence in the area.

Phylogeographic Substructuring in the Southernmost Refugium of the European Common Frog Rana temporaria.

Rana temporaria is one of the most widespread Palearctic brown frogs. We aimed to clarify distribution pattern of two main genetic clades in the understudied Balkan peninsula by using 16SrRNA and MT-CYTB sequences, already widely applied in analyses of populations from other parts of Europe, while focusing on the broad area along the Morava river (central Balkans) as a known gap in the species distribution. Additionally, we were interested in revealing the extent of haplotype diversity within the main genetic clades in the Balkans, particularly around the supposed suture zone. The results revealed a suture zone between the Western and Eastern Clades in the central part of the Balkan Peninsula. This indicated the existence of a historical barrier between the Balkan Mountain Belt and geographically close mountains surrounding the Vlasina Plateau (Rhodope/Serbian-Macedonian Massif). The overall observed haplotype diversity in populations of R. temporaria from the Balkan Peninsula seems high. Harboring both main genetic clades of R. temporaria qualifies the Balkan Peninsula as another important center of species' genetic diversity, as well as rich in unique haplotypes. This points out the necessity of applying conservation measures focused on the common European frog populations and habitats in this part of the species' distribution area.

Using genetic variation to infer associations with climate in the common frog, Rana temporaria.

Recent and historical species' associations with climate can be inferred using molecular markers. This knowledge of population and species-level responses to climatic variables can then be used to predict the potential consequences of ongoing climate change. The aim of this study was to predict responses of Rana temporaria to environmental change in Scotland by inferring historical and contemporary patterns of gene flow in relation to current variation in local thermal conditions. We first inferred colonization patterns within Europe following the last glacial maximum by combining new and previously published mitochondrial DNA sequences. We found that sequences from our Scottish samples were identical to (92%), or clustered with, the common haplotype previously identified from Western Europe. This clade showed very low mitochondrial variation, which did not allow inference of historical colonization routes but did allow interpretation of patterns of current fine-scale population structure without consideration of confounding historical variation. Second, we assessed fine-scale microsatellite-based patterns of genetic variation in relation to current altitudinal temperature gradients. No population structure was found within altitudinal gradients (average FST=0.02), despite a mean annual temperature difference of 4.5 °C between low- and high-altitude sites. Levels of genetic diversity were considerable and did not vary between sites. The panmictic population structure observed, even along temperature gradients, is a potentially positive sign for R. temporaria persistence in Scotland in the face of a changing climate. This study demonstrates that within taxonomic groups, thought to be at high risk from environmental change, levels of vulnerability can vary, even within species.

Surviving on the edge: present and future effects of climate warming on the common frog (Rana temporaria) population in the Montseny massif (NE Iberia).

The Montseny massif shelters the southernmost western populations of common frogs (Rana temporaria) that live in a Mediterranean climate, one which poses a challenge for the species' persistence in a scenario of rising temperatures. We evaluated the effect of climate change at three levels. First, we analysed if there has been an advancement in the onset of spawning period due to the increase in temperatures. Second, we analysed the impact of climatic variables on the onset of the spawning period and, third, how the distribution of this species could vary according to the predictions with regard to rising temperatures for the end of this century. From 2009 to 2021, we found there had been an increase in temperatures of 0.439 °C/decade, more than the 0.1 °C indicated by estimates for the second half of the previous century. We found an advancement in the onset of the reproduction process of 26 days/decade for the period 2009-2022, a change that has been even more marked during the last eight years, when data were annually recorded. Minimum temperatures and the absence of frost days in the week prior to the onset of the spawning period determine the start of reproduction. Predictions on habitat availability for spawning provided by climatic niche analysis for the period 2021-2100 show a potential contraction of the species range in the Montseny and, remarkably, much isolation from the neighbouring populations.

Exploring water-borne corticosterone collection as a non-invasive tool in amphibian conservation physiology: benefits, limitations and future perspectives.

Global change exposes wildlife to a variety of environmental stressors and is affecting biodiversity worldwide, with amphibian population declines being at the forefront of the global biodiversity crisis. The use of non-invasive methods to determine the physiological state in response to environmental stressors is therefore an important advance in the field of conservation physiology. The glucocorticoid hormone corticosterone (CORT) is one useful biomarker to assess physiological stress in amphibians, and sampling water-borne (WB) CORT is a novel, non-invasive collection technique. Here, we tested whether WB CORT can serve as a valid proxy of organismal levels of CORT in larvae of the common frog (Rana temporaria). We evaluated the association between tissue and WB CORT levels sampled from the same individuals across ontogenetic stages, ranging from newly hatched larvae to froglets at 10 days after metamorphosis. We also investigated how both tissue and WB CORT change throughout ontogeny. We found that WB CORT is a valid method in pro-metamorphic larvae as values for both methods were highly correlated. In contrast, there was no correlation between tissue and WB CORT in newly hatched, pre-metamorphic larvae, metamorphs or post-metamorphic froglets probably due to ontogenetic changes in respiratory and skin morphology and physiology affecting the transdermal CORT release. Both collection methods consistently revealed a non-linear pattern of ontogenetic change in CORT with a peak at metamorphic climax. Thus, our results indicate that WB CORT sampling is a promising, non-invasive conservation tool for studies on late-stage amphibian larvae. However, we suggest considering that different contexts might affect the reliability of WB CORT and consequently urge future studies to validate this method whenever it is used in new approaches. We conclude proposing some recommendations and perspectives on the use of WB CORT that will aid in broadening its application as a non-invasive tool in amphibian conservation physiology.

Special Nuclear Structures in the Germinal Vesicle of the Common Frog with Emphasis on the So-Called Karyosphere Capsule.

The karyosphere (karyosome) is a structure that forms in the oocyte nucleus-germinal vesicle (GV)-at the diplotene stage of meiotic prophase due to the assembly of all chromosomes in a limited portion of the GV. In some organisms, the karyosphere has an extrachromosomal external capsule, the marker protein of which is nuclear F-actin. Despite many years of theories about the formation of the karyosphere capsule (KC) in the GV of the common frog Rana temporaria, we present data that cast doubt on its existence, at least in this species. Specific extrachromosomal strands, which had been considered the main elements of the frog's KC, do not form a continuous layer around the karyosphere and, according to immunogold labeling, do not contain structural proteins, such as actin and lamin B. At the same time, F-actin is indeed noticeably concentrated around the karyosphere, creating the illusion of a capsule at the light microscopy/fluorescence level. The barrier-to-autointegration factor (BAF) and one of its functional partners-LEMD2, an inner nuclear membrane protein-are not localized in the strands, suggesting that the strands are not functional counterparts of the nuclear envelope. The presence of characteristic strands in the GV of R. temporaria late oocytes may reflect an excess of SMC1 involved in the structural maintenance of diplotene oocyte chromosomes at the karyosphere stage, since SMC1 has been shown to be the most abundant protein in the strands. Other characteristic microstructures-the so-called annuli, very similar in ultrastructure to the nuclear pore complexes-do not contain nucleoporins Nup35 and Nup93, and, therefore, they cannot be considered autonomous pore complexes, as previously thought. Taken together, our data indicate that traditional ideas about the existence of the R. temporaria KC as a special structural compartment of the GV are to be revisited.

Slow and steady wins the race: contrasted phylogeographic signatures in two Alpine amphibians.

A deeper phylogeographic structure is expected for slow-dispersing habitat specialists compared to widespread adaptable species, especially in topographically complex regions. We tested this classic assumption by comparing the genomic (RAD-sequencing) phylogeographies of 2 amphibians inhabiting the Swiss Alps: the mobile, cosmopolitan common frog (Rana temporaria) against the stationary, mountain endemic Alpine salamander (Salamandra atra). Our results ran opposite of predictions: the frog displayed significantly higher genetic divergences and lower within-population variation compared to the salamander. This implies a prominent role for their distinctive glacial histories in shaping intraspecific diversity and structure: diversification and recolonization from several circum-Alpine micro-refugia for the frog versus a single refugium for the salamander, potentially combined with better population connectivity and stability. These striking differences emphasize the great variability of phylogeographic responses to the Quaternary glaciations, hence the complexity to predict general patterns of genetic diversity at the regional scale, and the forces that underlie them.