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TERRA TYPICA. City Tiflis (= Tbilisi), Georgia. DISTRIBUTION. The main distribution range of the species occupies right-bank section of the valley of middle current of Kura River and the ravine of its right tributaries within Georgia, northern Armenia and north-western Azerbaijan. It covers the area from Gori in the west up to northern foothills of the ranges of the Lesser Caucasus in the lower and middle current of the rivers flowing into Kura River: Algeti, Khrami, Debeta, Akstafa-chai, Gyandzhachai and others in the south-east. Big population, isolated now from the main distribution range, is known in the valley of middle current of the left tributary of Kura River – river Iori on the southern slopes of the Zivgamborsky range. A great zoogeographical interest represents an isolated population of this species discovered in south-western Azerbaijan, in the ravine of upper current of Akar River, belonging to the basin of Aras River. Presence of D. portschinskii in the southern foothills of Lesser Caucasus can be connected with a radical reconstruction of river systems which was taking place on the territory of Transcaucasia in the postglacial period. The nominative subspecies D. p. portschinskii occupies the most part of the distribution range. In the ravines of right tributaries of Kura River – the rivers Mashavera in Georgia and Debeta in Armenia – occurs D. p. nigrita (Bakradze, 1976). CONSERVATION STATUS. On the most part of the distribution range the number is high and stable.

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Currently among sympatric populations of biparental species of genus Darevskia, which were involved in reticulate evolution, the processes of hybridization take place only between D. raddei and D. portschinskii species. The successful combination of parental species with low reproductive isolation may be considered as main factor explaining the origin of parthenogenetic species.

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The unique isolated population of racerunner Eremias arguta transcaucasica in Armenia is under strong human pressure and seeks urgent conservation measures. The population has a limited area (approximately 9 hectares) on the shore of Lake Sevan, in vicinity of a settlement. Հայաստանում բազմագույն մողեսիկի միակ և մեկուսացված պոպուլյացիան գտնվում է մարդածին գործոնի ուժեղ ազդեցության ներքո, և անհրաժեշտ են անհապաղ միջոցառումներ նրա պահպանության համար: Պոպուլյացիան գտնվում է Սևանա լճի ափին, բնակելի տարածքից ոչ շատ հեռու և գրավում է 9 հա տարածք: Единственно известная изолированная популяция разноцветной ящурки в Армении находится под сильным антропогенным прессом и требует срочных мер по ее охране. Популяция занимает ограниченную площадь (около 9 гектаров) на берегу озера Севан недалеко от населенного пункта.

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The new subspecies is fouпd in the mauпtain regions of south-eastern Georgia and northern Armenia. It differs from the nominative form Ьу а much darker соlош of the body upper side and Ьу certain peculiarities of the squamous cover.

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Head shape plays a crucial role in ecological and evolutionary processes in lizards, and scientists have studied head shape using traditional and 3D geometric morphometrics. Lizards are classic subjects for ecological studies because closely related and ecologically similar species coexist. Sympatric species tend to show higher levels of morphological divergence compared to allopatric species. In this study, we focus on two parthenogenetic Darevskia species (Darevskia dahli and Darevskia armeniaca) that share a maternal species, Darevskia mixta, but have different paternal species (Darevskia portschinskii and Darevskia valentini). We aim to assess the relative importance of morphologically inheritable traits and environmental conditions on head shape in these parthenogenetic species. Specifically, we aim to determine whether local adaptations or intermediate phenotypes between parental species drive head shape variation in parthenogens. To accomplish this, we analyze the head shapes of samples from both parthenogens, their paternal species, and their common maternal species from 3 sites in Georgia. Our study shows that certain aspects of head shape are associated with body size and habitat climate, with high mountain species exhibiting larger and deeper heads with stronger jaws regardless of breeding mode. In addition, both parthenogens exhibit narrower and more elongated jaw areas, flatter mandibles, and thus weaker jaws compared to females of their maternal and paternal species.

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We compared the life history components of small and large-bodied unisexual (Darevskia dahli and Darevskia armeniaca) and bisexual (Darevskia portschinskii, Darevskia valentini, and Darevskia obscura) Caucasian rock lizard species. Research objectives were to determine whether reproductive mode (bisexual or parthenogenetic), female body size, altitude and landscape of the habitat, or interaction of these factors determine the relative investment of energy into a single reproduction, number, and relative size of eggs. The research revealed the differences between two parthenogenetic species and their paternal bisexual lizards. However, the pattern did not coincide for the two studied lineages i.e., parthenogenetic D. armeniaca invests relatively more resources into reproduction than its paternal D. valentini. Simultaneously, reproductive effort of parthenogenetic D. dahli did not differ from its paternal D. portschinskii. Instead, D. dahli tended to produce more but lighter eggs than D. portschinskii. In both cases, the parthenogenetic form tended to follow a r-reproductive strategy, typical for lizards occupying less stable environments than their parental species. However, other interspecific differences such as body size or evolutionary distance shade these differences, and determine the pattern of divergence between a parthenogen and its bisexual relative. In particular, smaller body size constrains increased the reproductive effort, and parthenogenetic species shifted to a balance between egg size and number rather than between resources invested into a single reproduction event and the probability to survive until the next season.

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Two species of rock lizards, the parthenogenetic D. dahli and the sexually reproducing D. portschinskii, coexist in a rocky outcrop in an area of ca. 1 ha, in the vicinity of Tbilisi, Georgia; the location has been well-known since the middle 1960s. The population density of the parthenogenetic lizard is five times higher than that of the sexual breeder. We studied the distribution of active lizards in space and time over three consecutive years, during the spring and autumn activity periods, to explore spatial and temporal differ-ences between the species on a fine spatial scale. We studied the influence of temperature, humidity, and quantitative characteristics of the surface and the distance from permanent water source on the spatial distribution of D. dahli and D. portschinskii. Darevskia portschinskii was less dependent on the distance from the water source and more evenly distributed in space and time than D. dahli. Despite potential competitive interactions, the species did not avoid each other on the microhabitat scale, suggesting that the observed ecological differences are not caused by a niche shift. More individuals of the sexual breeder than individuals of the parthenogen were found in suboptimal habitats. This feature may increase the evolutionary success of D. portschinskii in a long-term perspective.

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The final part of a series of papers on the lizards of the Caucasus, that have been published in previous years. The paper reports on the life habits, capture and keeping in terraria of several lizards of Soviet Transcaucasia. In these respects the agamid Phrynocephalus helioscopus persi- cus and three species of the lacertid genus Eremias occuring in that area (i. e. strauchi, velox, pleskei) are discussed. Finally a !ist of all lizard species and subspecies actually known to occur in this region is given.

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In Georgia, 16 species of rock lizards of the Genus Darevskia are occuring (D. alpina, D. „armeniaca`, D. brauneri, D. caucasica, D. clarkorum, D. daghestanica, D. „dahli`, D. derjugini, D. mixta, D. nairensis, D. parvula, D. portschinskii, D. praticola, D. rudis, D. „unisexualis` and D. Valentini). Besides short presentations of the single species and hints on their distribution and habitats, also some systematic remarks are given.

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Georgia, its history and the nature are briefly described. This is supplied by a short overview of the country`s herpetological fauna, with particular attention to the especially diverse family of true lizards. At the end, brief description of our common trip to Georgia (May - Juny 2002) is given.

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Many regions of the former USSR still re- ceive little attention from Western visitors, herpetologists not excluded. For the Cau- casus Mountains this is all the more sur- prising since the area forms a zone where northern and Middle Eastern flora and fauna meet, and which is thus of considera- bly zoogeographical interest. Presently we find three larger states in the Caucasus: Georgia, Azerbaijan and Arme- nia. Turkey borders to the southwest, Iran to the southeast, and in the north it is the Russian federation. Various smaller parts claim independence. The Black Sea forms the natural western boundary, the Caspian Sea the eastern one. Herpetologically the Caucasus is historically well-known because of the work of Darev- sky and collaborators on the rock lizards (at the time still in the large genus Lacerta, now in Darevskia) and the discovery of the first case of parthenogenesis in vertebrates (DAREVSKY, 1967; DAREVSKII, 1978; DAREVSKY & KULIKOVA, 1961). Below we will concentrate on the results of our field trip to Georgia during the last two weeks of June 2003. Predictably, because of our common interest in the group, the lacertids will receive the most attention.

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A phylogenetic-comparative approach was used to assess and refine existing secondary structure models for a frequently studied region of the mitochondrial encoded large subunit (16S) rRNA in two large lizard lineages within the Scincomorpha, namely the Scincidae and the Lacertidae. Potential pairings and mutual information were analyzed to identify site interactions present within each lineage and provide consensus secondary structures. Many of the interactions proposed by previous models were supported, but several refinements were possible. The consensus structures allowed a detailed analysis of rRNA sequence evolution. Phylogenetic trees were inferred from Bayesian analyses of all sites, and the topologies used for maximum likelihood estimation of sequence evolution parameters. Assigning gamma-distributed relative rate categories to all interacting sites that were homologous between lineages revealed substantial differences between helices. In both lineages, sites within helix G2 were mostly conserved, while those within helix E18 evolved rapidly. Clear evidence of substantial site-specific rate variation (covarion-like evolution) was also detected, although this was not strongly associated with specific helices. This study, in conjunction with comparable findings on different, higher-level taxa, supports the ubiquitous nature of site-specific rate variation in this gene and justifies the incorporation of covarion models in phylogenetic inference.

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Background. From the genus Darevskia in the territory of Azerbaijan Republic noted 11 species (D. armeniaca, D. caucasica, D. chlorogaster, D. daghestanica, D. derjugini, D. portschinskii, D. praticola, D. raddei, D. rostombekovi, D. rudis, D. valentini). Information on the condition of rock lizards in the republic has not been updated for a long time. The aim of the work was to clarify the data on the distribution and abundance of these species in Azerbaijan.
Materials and methods. The research was carried in the Talysh Mountains (Lenkoran, Lerik and Yardimli districts of Azerbaijan in 2008–2011), in the Great Caucasus (Guba, Gusar, Gabala and Zagatala districts in 2013–2016), in the Minor Caucasus (Dashkesen, Gadabay and Tovuz districts in 2017–2018).
Results. On the basis of own data and analysis of literature sources the data on the distribution and number of rock lizards from the genus Darevskia in Azerbaijan are given. The authors note that the areas of forest lizards of the Talysh (D. chlorogaster and D. praticola hyrcanica) are being reduced and these species need legisla- tive protection. The extinct species for the territory of the Republic should be considered D. derjugini.

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The structure and evolution of a satellite DNA family was examined in lizards from the genus Darevskia(family Lacertidae). Comparison of tandem units of repeated DNA (satDNA), CLsat, in all species from the genus Darevskiahas shown that their variability is largely explained by single-nucleotide substitutions, which form about 50 diagnostic positions underlying classification of the family into three subfamilies. Maximum differences between the subfamilies reached 25%. At this level of tandem unit divergence in the subfamilies, no cross-hybridization between them was observed (at 65°C). The individual variability within one subfamily within the species was on average 5% while the variability between species consensuses within a subfamily was 10%. The presence of highly conserved regions in all monomers and some features of their organization show that satellites of all Darevskia species belong to one satDNA family. The organization of unit sequences of satellites CLsat and Agi160 also detected by us in another lizard genus, Lacerta s. str. was compared. Similarity that was found between these satellites suggests their relatedness and common origin. A possible pathway of evolution of these two satDNA families is proposed. The distribution and content of CLsat repeat subfamilies in all species of the genus was examined by Southern hybridization. Seven species had mainly CLsatI (83 to 96%); three species, approximately equal amounts of CLsatI and CLsatIII (the admixture of CLsatII was 2–5%); and five species, a combination of all three subfamilies in highly varying proportions. Based on these results as well as on zoogeographic views on the taxonomy and phylogeny of the Darevskia species, hypotheses on the evolution of molecular-genetic relationships within this genus are advanced.

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The genetic relatedness of several bisexual and of four unisexual Lacerta saxicola complexlizards was studied, using monomer sequences of the complex-specific CLsat tandem repeats and anonymous RAPD markers. Genomes of parthenospecies were shown to include different satellite monomers. The structure of each such monomer is specific for a certain pair of bisexual species. This fact might be interpreted in favor of co-dominant inheritance of these markers in bisexual species hybridogenesis. This idea is supported by the results obtained with RAPD markers; i.e., unisexual species genomes include only the loci characteristic of certain bisexual species. At the same time, in neither case parthenospecies possess specific, autoapomorphic loci that were not present in this or that bisexual species.

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New records of Darevskia alpina from the vicinities of Zemo Bachiani Village in South Ossetia are presented and discussed: D. brauneri from the place of the confluence of the Luhunistskale River into the Rion River in Georgia and vicinities of Ertso Lake in South Ossetia, D. pontica from the vicinities of Slavyansk-na-Kubani, Timashevsk, Novotitarovskaya Village, Poltavskaya Village and Burakovsky Village in Krasnodar Region, D. portschinskii nigrita from the vicinities of Kizilkilisa Village in Georgia, D. praticola from the vicinities of Tskhinval, Acrisheu Village, Malaya Gufta Village, Hetagurova Village and the southern slope of the Zonkar Ridge in South Ossetia. Information on an attempt to introduce D. pontica into the territory of Rostov-on-Don is provided.

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1. Sexual dimorphism and geographical variability in signs of external morphology are revealed in the species of the studied complexes of rock lizards. The most important for their diagnosis are the features of folidosis of the head. Interspecific and intraspecific differences in morphometric features, color and pattern of the body were detected. 2. In the phylogenetic analysis, the Darevskia (caucasica) samples were divided into the group of the northern slope of the Central Caucasus (D. caucasica), the East Caucasus (D. daghestanica), the Western Caucasus (D. alpina), the northern slope of the Central and Western Caucasus (D. alpina ). Reliable identification and significant genetic differences of D. caucasica and D. daghestanica samples favor their attribution to different species. Within D. alpina two groups with high genetic differences (distances) were identified. Inside Darevskia (saxicola) two lines are described, one of which is connected with the Crimea and the Western Caucasus (D. lindholmi-D. Brauneri), and the second - with the North and West Caucasus (D. saxicola-D. Szczerbaki). 3. As a result of the nomenclatural revision, the lectotype Lacerta praticola pontica, L. saxicola brauneri, L. saxicola daghestanica, L. saxicola lindholmi, and the neotype L. saxicola; Specific locations, years and authors of the description of a number of taxa have been refined. 4. It has been established that the studied supernumerary complexes include the following valid taxa: Darevskia (praticola) - D. pontica pontica, D. pontica hungarica, D. praticola praticola, D. praticola hyrcanica, D. praticola loriensis; Darevskia (caucasica) - D. alpina, D. caucasica caucasica, D. caucasica vedenica, D. daghestanica; Darevskia (saxicola) - D. brauneri brauneri, D. brauneri myusserica, D. saxicola, D. szczerbaki, D. lindholmi. Lacerta saxicola darevskii is regarded as a minor synonym for Lacerta saxicola brauneri. 5. For the first time accurate inventories of findings (1,443 locations) and GIS maps of species arealways were compiled, reliably characterizing the features of their distribution; The structure of areals, the current trends of their changes and the factors influencing the distribution of rock lizards are revealed. It is recommended to carry out conservation measures of international and national level in order to preserve the populations of D. alpina, D. brauneri myusserica and D. szczerbaki, especially in typical territories. 6. The first and only reliable paleontological find of Darevskia sp. - Darevskia sf. brauneri from the Pleistocene site, the caves of Mezmaiskaya. A hypothesis is proposed for the formation of species of complexes, according to which the isolation of their common ancestor from a hypothetical form it is logical to associate with the Miocene and Pliocene boundaries, or with the Cimmerian century of the Pliocene, 153 and the radiation of modern species - with the Akchagylian age, corresponding to the Piacenza and Gelazian tiers. The parallel formation of several Darevskia (praticola) and Darevskia (caucasica) lines around the Greater Caucasus is assumed in the early Pliocene. At the end of the Pontian age, the primary area of ​​the ancestor of the modern forms of Darevskia (saxicola) and the subsequent formation in the Mediterranean landscapes of the Black Sea coast, along the surviving cliff, D. szczerbaki, and the cuestas of the North Caucasus - D. saxicola, could have occurred at the periphery of the Caucasian peninsula.

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Hybridization is a common evolutionary process with multiple possible outcomes. In vertebrates, interspecific hybridization has repeatedly generated parthenogenetic hybrid species. However, it is unknown whether the generation of parthenogenetic hybrids is a rare outcome of frequent hybridization between sexual species within a genus or the typical outcome of rare hybridization events. Darevskia is a genus of rock lizards with both hybrid parthenogenetic and sexual species. Using capture sequencing, we estimate phylogenetic relationships and gene flow among the sexual species, to determine how introgressive hybridization relates to the origins of parthenogenetic hybrids. We find evidence for widespread hybridization with gene flow, both between recently diverged species and deep branches. Surprisingly, we find no signal of gene flow between parental species of the parthenogenetic hybrids, suggesting that the parental pairs were either reproductively or geographically isolated early in their divergence. The generation of parthenogenetic hybrids in Darevskia is, then, a rare outcome of the total occurrence of hybridization within the genus, but the typical outcome when specific species pairs hybridize. Our results question the conventional view that parthenogenetic lineages are generated by hybridization in a window of divergence. Instead,

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Considering all costs associated to sex, sexual reproduction could be expected to be rare. However, we find sexual reproduction to be pervasive in nature, and only a reduced number of taxa are completely asexual. In fact, the variety of sex reproductive systems, mating techniques and traits, reveals that the organisms’ reproduction has been an expressive target of selection and adaptation throughout evolution. Sex is selected because it facilitates adaptation in complex and changing environments (Weismann, 1889), and this has been already shown empirically in several models. However, studies and theories developed concerning the paradox of sex will not be able to clarify the current distribution and abundance of asexual lineages in nature. The understanding of rates of origin and extinction of asexual lineages, together with the putative differential evolution rates in organisms with sexual or asexual reproduction, should be considered in the main “origin of sex” question. The model used here, the genus Darevskia, is the first true parthenogenetic vertebrate described. It is a highly speciose genus, currently including 27 species, of which seven are parthenogenetic and of hybrid origin. Only a few of the sexual species contributed for the hybridization events which originated the parthenogens clonal lineages, and these were directional: the maternal species were always Darevskia raddei or D. mixta, and the paternal always D. valentini or D. portshinskii. Using a set of microsatellite and mtDNA markers, we first start to study the role of hybridization in the origin of vertebrate parthenogens, the extent of gene flow with sexual relatives and the relation between hybridization, asexuality and polyploidy, in the context of the main theories of asexual evolution proposed to date. We focus on the D. unisexualis, D. uzzelli and D. armeniaca parthenogens and polyploid backcrosses found in sympatric locations between the parthenogens and its sexual parentals. We find that only specific parental pairs are responsible for the origin of vertebrate parthenogenesis, regardless of their phylogenetic distance. Despite the recurrent hybridization presently reported in Darevskia, asexuality originated multiple times but only in a single temporal event the past. Parthenogenetic females are capable of backcrossing with sexual males, but can only produce polyploid individuals with reduced fertility that do not contribute for gene flow between parthenogens and sexuals. The sexual reproduction machinery can be lost with time in the parthenogenetic hybrids, which are most likely the result of a post-zygotic reproductive barrier to gene flow in the speciation continuum of Darevskia sexual species. In order to reconstruct the phylogenetic inference of this group, a set of capture sequence probes were designed from a transcriptome de novo assembly. Phylogenetic inference reconstruction has been extensively used to ask several evolutionary biology questions. However, despite the exponential use of high-throughput sequencing technologies and its promising applications in phylogenetics, next generation sequencing (NGS) techniques are still far from being as widely used in this field as in other areas of evolutionary genetics. The workflow developed in this thesis has proved to be not only cost-effective, but also to produce a very high number of cross genome phylogenetically informative markers in this non-model species. Finally, taking advantage of the hundreds of cross genome markers developed, a species tree was constructed and within genus relationships evaluated. Introgression tests showed a widespread pattern of gene flow across the genus, not only recent between recently diverged clades, but also both recent and ancient gene flow between early diverging Darevskia clades. Several evidences of hybridization with gene flow between diverging clades have been found in other systems. However, such widespread patterns where introgression has happened between all major clades, and in a very high number of species pairs, are not frequently found. It is also found that gene flow is completely absent between parthenogens sexual parental pairs. In groups with sexual-parthenogenetic reproducing species, pre- or post-zygotic reproductive barriers could be more difficult to attain and hybrid asexuality can, thus, effectively create reproductive barriers between diverging sexual taxa, that were likely faced with recurrent secondary contact. The work presented in this thesis shows that only a few sexual species pairs were responsible for the origin of the parthenogens, that some species acted always as the maternal species and others always as the paternal, that the phylogenetic distances between each pair are included in a wide range interval, and that introgression is found widespread across the genus but absent between the parental pairs. Regardless of the reproduction type, this study also shows the relevance and depth of hybridization during divergence. As has been shown intensively, gene flow is common during speciation and clades divergence. However, it would be interesting to analyse other groups together and test if deep branch gene flow is found only in some exclusive groups (such as sexual-asexual genera) or if it is something more widespread. This work presented here moves Darevskia towards providing a model that can be used to understand the origin of asexuality in vertebrates. Here the basis for future studies about sex and asexuality is provided, so that a focus on the differential evolution rates genomes of both reproduction mode can be analysed.

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A maximum parsimony phylogeny of 14 Caucasian species of rock lizards, genus Ijicerta, subgenus Archaeolacerta, was constructed from mitochondrial cytochrome b and ATPase 6 partial gene sequences. Congruence analyses were carried out between the two genes. A synthesis of the data sets reveals three well supported monophyletic groups: (1) the caucasica group including (Lacerta derjugini ((Lalpina, L. clarkorum) (L. caucasica, L. daghestanica))); (2) the rudis group including (L. parvula (L. portschinskii (L. vakntini, L. rudis))); and (3) the saxicola group including (L. mixta (L. nairensis (L. saxicola, L. raddeijj). Despite the diagnosis of three groups, the placement of L. praticola as a basal taxon is uncertain, as are the relationships among the three groups. The mitochondrial DNA sequence data suggested prior hybridization between L. mixta and L. alpina and possibly between L. saxicola and L. nairensis. Lacerta raddei was resolved as a paraphyletic species on the mtDNA tree; this may result from either hybridization or random gene sorting.

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The genus Darevskia comprises over 20 species of small-bodied lizards, mainly occurring in the Caucasus Mountain Region. They show differences in body size, scalation and coloration, however, fully diagnostic characters that could separate the species with a high confidence level are still lacking. The early phylogenetic hypothesis of this group was based on ‘traditional’ analysis of morphology, based on multiple body and head measurements and scalation traits. Later, a molecular phylogeny of the genus rejected some of the proposed topology based on morphological traits. In this paper, we used quantitative morphological data (outline-based shape data) to test phylogenetic similarities, as proposed by these earlier hypotheses. We analyzed the pileus shape and the anal area of more than 200 individuals, representing six species of Darevskia, using outline based elliptic Fourier analysis. The analysis did confirm a clustering of the individuals and species (using UPGMA) from the same mitochondrial DNA clade. Hence, the phylogenetic affinity of the major clades in Darevskia could be identified using both molecular methods and outline analysis, whereas a traditional quantitative morphological analysis could not.

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Geometric morphometrics is a better tool to evaluate the variation of shape than ‘traditional’ morphometrics. In reptiles, it outperforms morphometrics based on linear measurements and scalation. In an earlier study, two-dimensional outline-based geometric morphometrics in six species of rock lizards (Darevskia) showed that their shapes reflected the species divergence pattern. This allowed us to separate species from different clades, but we could not distinguish closely related species within a clade. We hypothesized that three-dimensional (3D) head shape data would be sufficiently discriminative to identify closely related species. To test this hypothesis, we compared head shapes of three closely related species of the ‘rudis’ clade, Darevskia portschinskii, Darevskia valentini and Darevskia rudis, with the last species treated as two distinct groups (D. r. obscura vs. D. r. rudis), using 3D landmark data. The 3D analysis isolated the species of the ‘rudis’ clade from each other and even separated individuals from populations that showed a genetic introgression pattern. The analysis showed that D. r. obscura is morphologically as distinct from D. r. rudis as from the other nominal species. For this reason, we suggest elevating the status of D. r. obscura to species level, i.e. Darevskia obscura Lantz & Cyrén, 1936.

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The two species of rock lizards, Darevsia raddei and Darevskia portschinskii, belong to two different phylogenetic clades of the same genus. They are supposed ancestors for the hybrid parthenogenetic, Darevskia rostombekowi. The present study aims to identify morphological features of these two species and the potential gene introgression between them in the area of sympatry. External morphological features provided the evidence of specific morphology in D. raddei and D. portschinskii: the species differed in scalation and ventral coloration pattern, however, they had some proportional similarities within both sexes of the two species. Males of both species had relatively larger heads and shorter bodies than females. Males of D. raddei were slightly larger than males of D. portschinskii and had longer hindlimbs. Microsatellite genotyping revealed no traces of hybridization or gene flow among these species. We suggest that the absence of individuals with combined morphological and genetic features of the studied species reflects existing reproductive barriers. The hybridization between two bisexual rock lizard species from distant clades is rare and only takes place under very specific environmental conditions.

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The parthenogenetic rock lizard Darevskia rostombekowi is considered to be the product of hybridization between female Darevskia raddei and male Darevskia portschinskii. These two species coexist within several secondary contact areas; however, no trace of their hybridization has been previously reported. We conducted focal observations of individually marked lizards in 2017 and 2018 to establish if there is behavioural isolation between these species. We demonstrate that individuals distinguish between lizards of the same and different species. Individuals of both studied species interacted regularly, but we found no evidence of males of either species using interspecific interference competition for resources or for females. Neutral reactions prevailed in the reactions of males to the individuals of the different species; aggressive or submissive behaviour was more common towards males of the same species. The differences in reactions of males to females of the same and different species were less clear and interspecific social interactions were almost as common as intraspecific interactions. Interspecific male mating behaviour was rare and unsuccessful; only a single female with heterospecific copulation marks on the body was found. The mating period in both species overlapped broadly in late May and early June; body size (SVL) in females of both species was equal. Hence, we suggest that the selection of the sexual partner and preference of the conspecific partner for the social and sexual contacts is the most plausible explanation of the revealed behavioural asymmetry in intra- and interspecific relationship.

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The Caucasian parthenogenetic rock lizards of the L. saxicola complex probably originated by hybridisation of some bisexual species. We verified this hypothesis using a new approach based on comparison of repetitive DNA characters, which produce species-specific patterns (named `taxonprint`). The method relies on restriction endonuclease hydrolysis of genomic DNA, with the following 32P-end labeling and polyacrylamide gel electrophoretic separation of the fragments. The parthenogenetic species L. armeniaca and L. dahli possess specific features both of putative maternal L. mixta (in some taxonprints), and of paternal L. valentini (in other ones), whereas L. portschinskii and L. rudis also could be the paternal species. Parthenoclones L. unisexualis and L. uzzelli have the specific DNA features in several taxonprints of L. raddei or L. nairensis (which cannot be discriminated by taxonprints) which are supposed to be maternal species for L. unisexualis and paternal ones for L. uzzelli. The specific features of L. valentini (or L. portschinskii) are observed in L. unisexualis; L. uzzelli has not been investigated in this respect. Parthenogenetic L. rostombekovi also possesses properties of L. raddei or L. nairensis, but we have not be able to find any features of supposed paternal L. portschinskii in this parthenogenetic species.

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Multiple band patterns of DNA repeats in the 20–500-nucleotide range can be detected by digesting genomic DNA with short—cutting restriction endonucleases, followed by end labeling of the restriction fragments and fractionation in nondenaturing polyacrylamide gels. We call such band patterns obtained from genomic DNA ‘‘taxonprints’’ (Fedorov et al. 1992). Here we show that taxonprints for the taxonomic groups studied (mammals, reptiles, fish, insects—altogether more than 50 species) have the following properties: (1) All individuals from the same species have identical taxonprints. (2) Taxonprint bands can be subdivided into those specific for a single species and those specific for groups of closely related species, genera, and even families. (3) Each restriction endonuclease produces unique band patterns; thus, five to ten restriction enzymes (about 100 bands) may be sufficient for a statistical treatment of phylogenetic relationships based on polymorphisms of restriction endinuclease sites. We demonstrate that taxonprint analysis allows one to distinguish closely related species and to establish the degree of similarity among species and among genera. These characteristics make to use this phenomenon for phylogenetic aims (Cooke 1975; Christie and Skinner 1979; Brown and Dover 1979, 1980; Elizur et al. 1982; Hembelen et al. 1982; Buckland 1983; Dandieu et al. 1984; Lima de Faria et al. 1984; Shubina and Mednikov 1986; Turner et al. 1991), but this approach has not been extensively applied. In this paper we have reexamined the problem on the basis of our own preliminary results, partly published in Russian journals, confirming the ideas about possible correlations between evolution of DNA repeats and speciation (Fedorov et al. 1992; Grechko et al. 1993; Potapov and Ryskov 1993). We have demonstrated that the modified method designated ‘‘DNA taxonprint’’ (Fedorov et al. 1992) can be effectively used for revealing species—specific genomic markers in different taxonomic groups. These taxonprint markers are found to be helpful for evaluation of the degree of species similarity between species, genera, and families. More than 50 species from different taxa were studied.

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The infections by blood parasites in sympatric populations of rock lizards D. raddei and D. portchinskii were studied. 121 adult individuals have been observed. Infection by blood parasites depends on sex of host. D. raddei species is more infected than D. portchinskii.

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The life and work of the Alsatian Louis Amédée Lantz (1886-1953), a pioneer of European herpetology. A trained and professional research-chemist, the Alsatian Louis Amédée Lantz was an active and particularly dynamic herpetologist. His residence of nearly twelve years in Russia enabled him to make several field trips to regions such as the Caucasus and Iran. He always carried with him a home made telescopic net that he used to catch lizards. That net became symbolic of Lantz for most people around him. He realized significant herpetological collections mainly deposited in the Museum of the Zoology Institute of the Russian Academy of Sciences in St. Petersburg. Soon after the Russian Revolution in 1917, he had to leave the country and stayed for a few years in France before joining England. During this period, Lantz visited the French Pyrenees and the Mediterranean border (Hyeres Islands, Bandol), enabling him to discover for the first time oviparous populations of common lizard and also to describe a new species of lizard from the French Pyrenees. Lantz is also at the origin of the discovery of unisexual reproduction by parthenogenesis in reptiles. His collaboration with the Swedish amateur herpetologist Otto Cyrén, whom he met through the German herpetologist Willy Wolterstorff, was particularly successful throughout his career. Lantz died at the age of 66 years, in Switzerland, as he was about to join the team of herpetologists at the Natural History Museum in Paris.

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The study of genome size variation in cells of vertebrates using the DNA flow cytometry makes it possible to precisely determine polyploid individuals, which is extremely important when studying the processes of reticulate speciation. In addition, in many groups of vertebrates, closely related species often differ in the nuclear DNA content. Therefore, the purpose of our study was to explore the variability of genome size and ploidy in populations of 29 species and subspecies of mountain lizards of the genus Darevskia, as well as their hybrids. As a result of the study, the range of variability in individuals of different ploidy (91% of diploid and 9% of triploid individuals) was established not to overlap. Among diploid species, no correlation was found between the nuclear DNA content and phylogenetic relationships, geographic coordinates, altitude, average annual temperatures and precipitation. Representatives of all studied species complexes (with the exception of D. adjarica) had approximately the same limits of variability. Two species (D. derjugini and D. saxicola) show significant intraspecific variability. Comparisons of the genome size of parthenogenetic and bisexual species generally revealed no noticeable differences between them. Studies of triploid hybrids have shown that their genome size as a whole roughly corresponds to the sum of the average size of the diploid genome of the maternal parthenogenetic species and the haploid genome of the paternal species. The variability of genome sizes within samples of triploid hybrids was on average slightly higher than in most parthenogenetic species, but some lower than in bisexual species. The paper discusses peculiarities of reticulate speciation in this group of animals.

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Genetic diversity at 37 allozyme loci was surveyed from Lacerta valentini (4 populations), L. portschinskii and L. rudis (1 population each). The number of polymorphic loci ranged from 1 (L. valentini) to 11 (L. rudis). Mean heterozygosity (direct count) ranged from 0.003 (L. valentini) to 0.071 (L. rudis). Nei`s (1978) genetic distance ranged from 0-0.03 among populations of L. valentini, 0.127-0.163 between L. valentini and L. rudis and 0.366-0.487 between L. portschinskii and the two other taxa. Indices of genetic variability for species having disjunct distributions were lower than in species with contiguous distributions, similar to the case of insular populations, which have lower values than do mainland populations.

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Genetic diversity at 37 allozyme loci was surveyed in Lacerta portschinskii from contiguous populations and from a disjunct population. Indices of genetic diversity (heterozygosity, number of alleles per locus, and percentage of loci polymorphic) were greater in contiguous populations than in the smaller disjunct population. In this regard, disjunct populations appear to be similar to island populations. Indices of genetic diversity in Caucasian Lacerta are less than those reported from vagile lizard taxa and more similar to those of sit-and-wait predators.

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The Bov-B LINE retrotransposon was first discovered in Ruminantia and was long considered to be specific for this order. Later, this mobile element was described in snakes and some lizard species. Analysis of phylogenetic relationships of Bov-B LINE elements from different ruminants, snakes, and lizard species led to the suggestion on horizontal transfer of this retrotransposon from Squamata to Ruminantia. In the Squamata group, Bov-B LINE element was found in all snakes and some lizard species examined. The element was not detected in the genomes of some species of the genera Lacerta and Podarcis. In the present study, using PCR amplification and sequencing of PCR products, Bov-B LINE element was identified in the genomes of parthenogenetic and bisexual species of the genus Darevskia (Lacertidae), as well as in such species as Lacerta agilis and Zootoca vivipara, where this retrotransposon had not been not detected before.

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The Caucasian rock lizard species Darevskia portschinskii is one of the bisexual species participating in interspecific hybridisation as the paternal ancestor with the maternal ancestors D. mixta and D. raddei resulting in the successful formation of the parthenogenetic D. dahli and D. rostombekowi, respectively. Populations of D. portschinskii have been previously divided into two subspecies, D. p. portschinskii and D. p. nigrita according to their geographical distribution and the morphological data, but they have not been characterised genetically. Here, we used ten microsatellite markers to determine the genetic structure of the D. portschinskii populations. The utility of the developed microsatellite markers for investigating the genetic variability within and among populations with a heterogeneous spatial distribution was demonstrated. Our results showed that the intra- and interspecific differentiation of the studied populations were consistent with the morphological data on the subspecies status of the D. p. portschinskii and D. p. nigrita populations. A potential applicability of the developed microsatellite markers to study genetic diversity of Darevskia species and subspecies complexes is suggested.

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Investigated the albumins from 31 species and subspecies of the genus Lacerta s.1. by means of the immunoloical techniue Micro-Complement-fixation. Dendrograms were computed by means of the ktch-MargJiash algorithm. Moreover the taxa of the Lacerta saxicola and the Lacerta danfordi comlexes were analyzed by electrophoresis concerning 14 genetic loci. The results were discussel together with karyological and genitalmorphological data so far known yielding the following relationships: Lacerta graeca shows a closer relationshi to the subgenus Podarcis as does the quite closely related species air L. dugesii and L. perspicikata. Lacerta Iaevis probabl is connected closely to Podarcis, too. Lacerta parva shows a closer relationship to the `small izards` than to the sub-genus Lacerta s. str. A clear decision concerning the position of the Lacerta danfordi complex according to chemosystematical data was not possible. It is isolated from the other species probably about as long as L. puma. Biochemical differences between its `species` are too small to confirm their taxonomical revalorisation by Eiselt and Schmidtler Within the Lacerta saxicola complex the investigated taxa show a close relationship. Lacerta praticola and L. derjugini were definitly assigned to this group.

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Aim Body size is instrumental in influencing animal physiology, morphology, ecology and evolution, as well as extinction risk. I examine several hypotheses regarding the influence of body size on lizard evolution and extinction risk, assessing whether body size influences, or is influenced by, species richness, herbivory, island dwelling and extinction risk. Location World-wide. Methods I used literature data and measurements of museum and live specimens to estimate lizard body size distributions. Results I obtained body size data for 99% of the world`s lizard species. The body size–frequency distribution is highly modal and right skewed and similar distributions characterize most lizard families and lizard assemblages across biogeographical realms. There is a strong negative correlation between mean body size within families and species richness. Herbivorous lizards are larger than omnivorous and carnivorous ones, and aquatic lizards are larger than non-aquatic species. Diurnal activity is associated with small body size. Insular lizards tend towards both extremes of the size spectrum. Extinction risk increases with body size of species for which risk has been assessed. Main conclusions Small size seems to promote fast diversification of disparate body plans. The absence of mammalian predators allows insular lizards to attain larger body sizes by means of release from predation and allows them to evolve into the top predator niche. Island living also promotes a high frequency of herbivory, which is also associated with large size. Aquatic and nocturnal lizards probably evolve large size because of thermal constraints. The association between large size and high extinction risk, however, probably reflects a bias in the species in which risk has been studied.

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The phylogeny of 12 species of Caucasian rock lizards and ground lizards, genus Lacerta, subgenus Archacolacerta, was determined from allozyme data. Three additional species of Lacerta Sorlned the outgroup. Of the 35 loci resolved, 20 were phylogenetically informative. Permutation tail probabilities calculated using Hennig86 and RandomCladistics and g, statistics obtained in PAUP revealed significant pattern in the data. Our analysis resolved 12 most parsimonious trees; among which were three well-supported monophyletic groups: I) (Lacerta alpina, L. caucasica, L. daglzestanica) [the L. caucasica group]; 2) (L. mixta. L. saxicola. L. raddei-nairensis) [the L. saxicola group]; and 3) (L. parvlila, L. portschinskii (L. valentini, L. rudis)) [the L. ruciis group]. The second and third groups formed a clade. The ground lizards L. praticola and L. derj~cginwi ere resolved as ingroup members. but their placement in the globally most parsimonious trees was ambiguous. A preferred tree was chosen by alternately pruning L. praticola and L. devugini from the tree. In doing so, L. praticola was resolved as the sister taxon of the L. calccasica group; and L, derjligini was resolved as the sister taxon of the clade containing the L. snxicola and L. rrldis groups. Our results are somewhat congruent with the morphology-based phylogeny of Darevsky (1967).

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In this work, we tested the conditions for fulfilling the concept of geographic parthe- nogenesis by a comparative analysis of the breadth of the ecological niches of parental and par- thenogenetic lizards of the genus Darevskia with a various number of established hybridization events. Estimates of the breadth of ecological niches of the parthenogenetic species D. ros- tombekowi Nb = 0.6(±0.08) and parental bisexual species D. raddei raddei – Nb = 0.86(±0.9), D. portschinskii – Nb = 1.21(±0.17) showed that for this parthenogenetic species one of the most important conditions of geographic parthenogenesis is fulfilled, i.e. the niche breadth of the parthenogenetic species is smaller than its parental bisexual species. The niche breadth of another parthenogenetic species D. dahli Nb = 0.86(±0.12) is smaller than that of the «paternal» species D. portschinskii – Nb = 1.21(±0.17), but larger than that of the «maternal» species D. mixta Nb = 0.48 (±0.08), which only partially agrees with the condition of geographic par- thenogenesis. This mismatch is due to the fact that D. dahli was formed as a result of several independent hybridization events, which resulted in the formation of multiple clonal lines de- rived from different parental pairs of D. portschinskii and D. mixta.

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After a brief description of Georgia’s landscape the author reports on the lizards of the family Lacertidae that were found during a herpetological trip in May 2012. In addition, a list of the recorded herpetological taxa is presented.

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An integrated approach for constructing maps of suitable habitats and ecological niches of parthenogenetic and their parental species of the genus Darevskiain the Caucasus is presented. It is shown that this approach is a powerful tool for analyzing species-specific requirements of lizards for the habitat and differentiating their niches in the multidimensional space of predictor variables.

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Caucasian rock lizards of the genus Darevskia are unique taxa, including both bisexual and parthenogenetic species. The parthenogenetic species have originated as a result of natural hybridisation between females and males of different bisexual species. The species involved in interspecific hybridisation are called parental. However, sympatric zones (SZ) of unisexual and bisexual rock lizards of the Caucasus are still poorly studied, although they are very important for understanding the role of hybrid individuals of different origin in reticulate evolution. This paper presents the location of the SZs of parthenogenetic and their parental bisexual rock lizards of the genus Darevskia in Armenia and adjacent territories of Georgia and Nagorno-Karabakh. We summarised the locations of the SZs identified from 1957 to the present, based on our field survey data gathered in 2018-2019 and records from publications and museum collections. This dataset includes 39 SZs of three types: SZ of parental bisexual species, SZ of parental species with unisexual species and SZ of the parthenogenetic species. For each zone, species composition, geographical and altitudinal distribution are presented. New records expand our knowledge of the geographical and altitudinal distribution of SZs in these species and provide additional data for understanding the mechanisms of reticulate evolution and hybridogeneous speciation in the past, present and future.

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Anatolia is characterized by a complex topological structure and a wide diversity of climatic regions. This geological context has been crucial during the evolution of the rock lizard genus Darevskia, promoting the origin of several species within this group of lizards. Our study focuses on the evolutionary history of the rudis species complex, comprised by Darevskia rudis, D. valentini and D. portschinskii, distributed across Anatolia and the Caucasus, with overlapping ranges. Previous studies have suggested the existence of ancient gene flow between these taxa, which, allied with poor sampling, led to weakly resolved phylogenies and mismatching topologies. Here, we employ two mitochondrial (cytb and ND4) and two nuclear (MC1R and C‐mos) DNA fragments, coupled with ecological niche modelling and a significant representation of the species’ wide distribution range to further assess relationships. The specimens identified either as Darevskia rudis or as D. valentini appear as paraphyletic and substructured into four clades, which started to differentiate during the lower Pleistocene (around 1.3 Mya). We also differentiate genetically the recently described Darevskia bithynica and identify the Kizil River valley as a strong vicariant candidate to explain the origin of this species by allopatric speciation. Moreover, the eastern Black Sea Mountains seem to have played an important role as glacial refugium for several populations of D. rudis. Overall, the present study confirms the circum‐Black Sea as a potential Pleistocene refuge and supports the refugia‐within‐refugia hypothesis with the finding of several geographically coherent evolutionary units in the region.

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The hypothesis of hybridogenous origin of lacertid parthenogenetic species was verified by RAPD method with several arbitrary primers. The hypothesis appeared to be correct as both parthenogenetic lizard DNAs contain only the RAPD loci of putative parental bisexual species and practically no ones specific for parthenospecies. The most probable parentals are L. mixta and L. portschinskii for L. dahli, and some of the populations of L. raddei/nairensis complex and L. portschinskii, too, for L. rostombekovi.

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Experimental data on the molecular structure and variability of microsatellite loci in unisexual and bisexual lizard species of the genus Darevskia were analyzed. The allelic variants of Du281 and Du47 were found to differ in the number of monomers, the structure of microsatellite clusters, and point mutations in these clusters and flanking DNA. Interspecific comparison of alleles of these loci revealed both variable regions in the microsatellite clusters and allele-specific evolutionarily conserved nucleotide groups. In general, the results of comparative structural analysis of allelic variants testify to a high genetic similarity of the unisexual and bisexual lizard species studied and reveals the characteristic features of their interspecies variability.

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Parasitological studies of 6 species of parthenogenetic and bisexual rock lizards of Armenia were carried out. The Helminthic and blood-parasite infections of these lizards were compared.

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Endoparasites of 10 reptiles species were studied. Two classes of helminths (Nematoda and Cestoda) were found. Extensity and intensity of infection were investigated.

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According to the synthesis of 30 years of multidisciplinary studies parthenogenetic species of rock lizards of genus Darevskia were formed as a result of different combination patterns of interspecific hybridization of the four bisexual parental species: D. raddei, D. mixta, D. valentini, and D. portschinskii. In particular D. portschinskii and D. raddei are considered as the parental species for the parthenogenetic species D. rostombekowi. Here for the first time we present the result of comparative immunocytochemical study of primary spermatocyte nuclei spreads from the leptotene to diplotene stages of meiotic prophase I in two species: D. portschinskii and D. raddei. We observed similar chromosome lengths for both synaptonemal complex (SC) karyotypes as well as similar number of crossing over sites. However, unexpected differences in the number and distribution of anti-centromere antibody (ACA) foci were detected in the SC structure of bivalents of the two species. In all examined D. portschinskii spermatocyte nuclei, one immunostained centromere focus was detected per SC bivalent. In contrast, in almost every studied D. raddei nuclei we identified three – nine SCs with additional immunostained ACA foci per SC bivalent. Thus, the obtained results allow us to identify species-specific karyotype features, previously not been detected using conventional mitotic chromosome analysis. Presumably the additional centromere foci are result of epigenetic chromatin modifications. We assume that this characteristic of the D. raddei karyotype could represent useful marker for the future studies of parthenogenetic species hybrid karyotypes related to D. raddei.

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Elements of the herpetofauna are in the author`s opinion of great importance for the zoogeographical division of the Palaearctic region. It is suggested that this region be divided into the following four subregions: 1/ arctic, 2/ boreal Euro-Siberian, 3/ bo- real Himalayan-Manchurian and 4/ Mediterranean-Central-Asiatic.

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We compared the distributions, abundances and ecological requirements of parthenogenetic lizard Darevskia ‘dahli’ and its bisexual progenitors, D. portschinskii and D. mixta, in Georgia. We developed a regression model relating the species abundances with the distribution of climates. Darevskia portschinskii lives in warmer and drier climates than D. mixta; D. ‘dahli’ has the intermediate requirements. Temperature is more important than humidity for D. portschinskii, humidity is more important for D. mixta and both temperature and humidity are important for D. ‘dahli’. Suitable habitats of all three species overlap broadly; however, the observed ranges partly overlap only for D. ‘dahli’ and D. portschinskii. The observed abundance of each species, related to its predicted abundance, is lower at the sites with potential competitors. Darevskia ‘dahli’ occupies a higher proportion of the suitable habitats and has higher abundances than the progenitor species. Competition with D. ‘dahli’ is an important factor determining current distribution pattern of D. portschinskii and D. mixta. The parthenogen is a stronger competitor than the bisexual breeders and potential advantages of the bisexual reproduction remain unrealized in the given temporal and spatial scale. To explain domination of bisexually breeding lizards on the global scale, considering climate changes in geological timescale is necessary.

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The difference between phenotypic and genotypic differentiation of conspecific populations is commonly used for detecting natural selection. However, phenotypic variation integrates both genetic and nongenetic components, and this may lead researchers to false conclusions. To avoid bias, the analysis of the heritability of individual phenotypic characters is important, but the means are labor-intensive and require controlled crosses. In this paper, we tried to get around these difficulties by working with natural system comprised of the coexisting sexually reproducing lizard Darevskia portschinskii, and its daughter parthenogenetic form, Darevskia dahli. The excess of individual and between-population variation in the sexual form relative to the parthenogen was used as a measure of heritability of each of 21 scalation traits and principal components extracted from their analysis. We compared these data with microsatellite genotypes based on the analysis of five variable loci. We showed that D. portschinskii had higher individual and between-population phenotypic diversity than D. dahli. Phenotypic differences between populations of D. portschinskii (but not D. dahli) correlate with both the geographic distances and pairwise fixation indices based on the analysis of the genetic markers. This correlation substantially increased when, instead of the original phenotypic distances, the corrected Qst values are used to assess the heritability of the characters. A similar analysis pattern is recommended for various natural systems with coexisting sexually and asexually reproducing organisms.

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Phenotypic evolution can cause either divergent or convergent phenotypic patterns. Even adaptation to the same environment may result in divergence of some elements of phenotype, whereas for other morphological traits it could cause phenotypic convergence. We hypothesize that at least some phenotypic characters diverge monotonically, hence they evolve irreversibly even in very closely related species, and this happens in spite of multiple convergent adaptive patterns. We studied the evolution of phenotype in 13 closely related Caucasian rock lizards (Darevskia), whose phylogenetic relationships are well known. We used head shape and the outlines of three important scales, using geometric morphometrics. We studied the association of the overall head shape, individual principal components of head shape and scale outlines with four predictors: phylogeny, habitat, sex and size. The overall head shape was not correlated with any of these predictors, whereas some principal components were correlated with habitat or phylogeny. Habitat type explained the highest fraction of variation in head shape and anal scale area. The relatedness inferred from the components of phenotype not correlated with habitat was congruent with the phylogenetic tree inferred from molecular data. Although adaptation to local environments may obscure the phylogenetic signal present in phenotype, there are components of phenotype whose evolution is irreversible

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Given sufficient time and limited gene flow, evolutionary lineages tend to transform into separate species. Mechanisms preventing assimilation during repeated gene-flow events include divergent adaptations and the development of pre- or postzygotic isolation. We analysed the morphological and genetic boundaries of three species of the rock lizard clade Darevskia ‘rudis’ (Darevskia rudis, Darevskia valentini, and Darevskia portschinskii) in relation to the environment, and tried to reconstruct evolutionary pathways underlying the observed separation among the species. We studied the geographic distribution of the scalation traits, microsatellite genotypes, and mitochondrial haplotypes. Our analyses showed consistent morphological and genetic patterns at the centre of the ranges for each species, but asymmetric distribution of alleles and scalation characters within the current contact zones among the species. The genetic and morphological diversification of the clade has been shaped during glacial isolation in an area of Southern Caucasus, away from the Black Sea Coast. The ancestral lineage of D. portschinskii separated from the common D. rudis–D. valentini lineage in the middle Pleistocene, and the two latter lineages separated in relatively recent geological time. Neither of the lineages attained complete lineage sorting; moreover, isolation and migration modelling have helped to detect recombinant gene flow from D. rudis to D. portschinskii (but not to D. valentini). This is most likely linked with climatically more similar suitable habitats between D. rudis and D. portschinskii than between D. valentini and the other two species. In itself, the isolation period was insufficient for the development of intrinsic isolation mechanisms in the system studied. Thus, differential landscape-dependent selection within the contact zones is likely to have triggered the rapid development of isolation mechanisms.

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Background: The majority of parthenogenetic vertebrates derive from hybridization between sexually reproducing species, but the exact number of hybridization events ancestral to currently extant clonal lineages is difficult to determine. Usually, we do not know whether the parental species are able to contribute their genes to the parthenogenetic vertebrate lineages after the initial hybridization. In this paper, we address the hypothesis, whether some genotypes of seven phenotypically distinct parthenogenetic rock lizards (genus Darevskia) could have resulted from back-crosses of parthenogens with their presumed parental species. We also tried to identify, as precise as possible, the ancestral populations of all seven parthenogens. Results: We analysed partial mtDNA sequences and microsatellite genotypes of all seven parthenogens and their presumed ansectral species, sampled across the entire geographic range of parthenogenesis in this group. Our results confirm the previous designation of the parental species, but further specify the maternal populations that are likely ancestral to different parthenogenetic lineages. Contrary to the expectation of independent hybrid origins of the unisexual taxa, we found that genotypes at multiple loci were shared frequently between different parthenogenetic species. The highest proportions of shared genotypes were detected between (i) D. sapphirina and D. bendimahiensis and (ii) D. dahli and D. armeniaca, and less often between other parthenogens. In case (ii), genotypes at the remaining loci were notably distinct. Conclusions: We suggest that both observations (i-ii) can be explained by two parthenogenetic forms tracing their origin to a single initial hybridization event. In case (ii), however, occasional gene exchange between the unisexual and the parental bisexual species could have taken place after the onset of parthenogenetic reproduction. Indeed, backcrossed polyploid hybrids are relatively frequent in Darevskia, although no direct evidence of recent gene flow has been previously documented. Our results further suggest that parthenogens are losing heterozygosity as a result of allelic conversion, hence their fitness is expected to decline over time as genetic diversity declines. Backcrosses with the parental species could be a rescue mechanism which might prevent this decline, and therefore increase the persistance of unisexual forms.

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Lacerta portschinskii and L. raddei co-occur at two localities north of Lake Sevan in the Armenian S. S. R. Electrophoretic patterns of hemoglobin, mannosephosphate isomerase, glucosephosphate isomerase, lactate dehydrogenase, and peptidases specific for leucyl-tyrosine and leucyl-glycyl-glycine distinguish these taxa and reveal no evidence of hybridization where the taxa are sympatric. The two taxa thus are not conspecific, although both are usually considered races of Lacerta saxicola.

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Five proteins (mannosephosphate isomerase, glucosephosphate isomerase, lactate dehydrogenase, creatine kinase, hemoglobin) were examined for six bisexual Transcaucasian taxa related to Lacerta saxicola (Lacerta valentini, L. portschinskii, L. raddei raddei, L. r. nairensis, L. mixta, L. parvula) and four unisexual taxa (Lacerta armeniaca, L. dahli, L. rostombekovi, L. unisexualis). Heterozygosity in the bisexual taxa was very limited for this sample of proteins. All individuals examined of each unisexual were heterozygous at loci specifying at least two of these proteins (L. armeniaca: mannosephosphate isomerase and creatine kinase; L. dahli, mannosephosphate isomerase and hemoglobin; L. rostombekovi, glucosephosphate isomerase, mannosephosphate isomerase and hemoglobin; L. unisexualis, glucosephosphate isomerase, mannosephosphate isomerase and creatine kinase). High levels of heterozygosity in unisexuals appears to result from the hybrid origin of the unisexuals. The exact combinations of alleles present in unisexuals would readily result from certain crosses among the bisexuals, and from no others. The first point supports the hypothesis that hybridization accounts for the observed heterozygosity, the second identifies, biochemically at least, the probable parents. On these biochemical grounds, L. armeniaca arose by hybridization of L. valentini and L. mixta; L. unisexualis from L. valentini and L. r. nairensis; L. rostombekovi from L. r. raddei and L. portschinskii; and L. dahli from L. portschinskii and L. mixta. With regard to altitudinal distribution, vegetational associations and geographic distribution, each unisexual species appears to be intermediate between its putative parental species. L. armeniaca, L. unisexualis and L. rostombekovi all live in drier situations than either parental species. L. dahli is an exception since it occupies slightly more moist habitats than L. portschinskii. Biogeographical considerations appear to place the age of L. unisexualis and L. rostombekovi at greater than 5000 years. It is possible that their occupancy of more extreme habitats than their parental species represents a relic ecology, reflecting the adaptations of the parental bisexual species when the unisexual species arose, rather than a weed habitat into which they moved to escape from competition with their parental species. The fixed heterozygosity of the unisexual species of Lacerta indicates that the restitution of somatic diploidy results either from a premeiotic endoduplication without cytokinesis, or from fusion of the female pronucleus with one of the second division meiotic products of the first polar nucleus. The first mechanism is inconsistent with the number of bivalents reported, the second is otherwise unknown in organisms in which the first polar nucleus becomes a polar body. The bisexual taxa are treated as several distinct species, four pairs of which are partly sympatric with little or no hybridization. Morphological and ecological differences between the other taxa are so great that there seems little question about specific distinctness. The degree of biochemical and morphological difference between these non-sympatric taxa is as great as that between those that do occur sympatrically without fusing. The formation of parthenogenetic species as a result of past hybridization between some pairs indicates a great selective disadvantage to these pairs of hybridizing, and is thus compelling evidence that the two members of each pair are not conspecific.

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We genotyped multiple populations of all seven parthenogenetic species of rock lizards, genus Darevskia, as well as their putative sexual parental populations, using double digest RAD sequencing genomic markers. Taking advantage of the conserved homology of the ZW/ZZ sex chromosomes among lacertid lizards, we aligned our short sequence reads to a reference Z chromosome assembly of the common wall lizard Podarcis muralis. This provided unique insight into the origin of all-female hybrid populations, which inherited their single Z chromosome exclusively from a paternal ancestor. The mapped Z-linked loci were used to construct a robust time-calibrated phylogeny. In each parent–offspring species pair, the geographically nearest population of the paternal species was identified as the most likely ancestor of the respective parthenogen, mirroring the trend observed previously on the maternal side in mitochondrial DNA. The estimated splits between the sampled paternal sexual ancestors and their daughter species occurred much earlier than suggested previously and during two narrow time periods: (1) the parthenogenetic Darevskia armeniaca, D. dahli, D. uzzelli and D. rostombekowi dated back to ~0.5 or ~0.9 Mya, depending on the calibration point used, while (2) D. bendimahiensis, D. sapphirina and D. unisexualis appear to have diverged ~1 or ~2 Mya.