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TERRA TYPICA. Settlement Shagaly, Armenia. DISTRIBUTION. It is comparatively widely distributed in the north Armenia and southern Georgia up to the foothills area in the valley of Kura River in the north. The recent distribution range is divided into some isolated populations. CONSERVATION STATUS. On the most part of the distribution range the number is stable.

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Age determination based on counting the annual layers in the femur was performed for three parthenogenetic species of Armenian rock lizards, Lacerta armeniaca (n = 147), L. unisexualis (n = 68), and L. dahli (n = 18), and for two bisexual species, L. nairensis (n = 29) and L. raddei (n = 32). Comparison of parthenogenetic and bisexual species shows that the growth rate, sexual maturity age, and life longevity in rock lizards are independent of the type of reproduction. The examined Lacerta species reach maturity by the second or third year of life. The maximum age of individuals in the samples studied is 7 and 5 years for L. armeniaca and L. nairensis, respectively, and 6 years for L. unisexualis, L. dahli, and L. raddei.

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The age of the parthenogenetic species, Lacerta armeniaca (N = 147), L. unisexualis (N = 68), and L. dahli (N = 18), and that in the bisexual species, L. nairensis (N = 29) and L. raddei (N = 32), were determined from femur bone layers. Parthenogenesis does not influence the growth rate, age of sexual maturation and longevity of rock lizards. The species of lizards under study reach sexual maturity during the second or third year of life. The maximum age of individuals in the samples studied was 7 years for L. armeniaca, 6 years for L. unisexualis, L. dahli, L. raddei, and 5 years for L. nairensis.

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Ilya S. Darevsky co-described 70 taxa (three genera, 46 species, 21 subspecies) in 44 publications belonging to five orders, eight families of amphibians and reptiles during his career in herpetology. Of this number, three taxa are fossil and 57 taxa are currently considered as valid. By the regions where new taxa were discovered Southeast Asia and Western Asia (includes Caucasus and Asia Minor) dominates. The largest number of descriptions was published in the Russian Journal of Herpetology.

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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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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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The study of the sympatric population, located in the Ijevan region of Armenia, where the bisexual species D. raddei coexists with three partenogenetic species - D. rostombekovi, D. dahli and D. armeniaca has shown that in this population a hybridization process is taking place between the D. raddei and D. rostombekowi species. Of the captured 104 D. rostombekowi in the study area, 18 triploid hybrid males have been found. A comparative study of the smears and histological slides prepared from the testicles of 9 hybrid males has detected their possible fertility. The recorded triploid hybrid males could potentially play important role in hybrid speciation.

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Four parthenogenetic subspecies of Lacerta . saxicola Eversmann (Transcaucasia) have closely overlapping sympatric ranges. The lizards show no intermediate forms in zones of their mutual habitat. On the border - line of their ranges parthenogenetic lizards can mate with males of neighbouring bisexual forms of Lacerta saxicola, producing hybrids that always are sterile triploid (3n=57) females. Therefore, application of geographical and physiological species criteria to parthenogenetic forms allows to regard them as independent species. However, geographical .and physiofogiical criteria are based on the effect of reproductive isolation mechanisms whose realization is possible upon the occurrence of both sexes in the population. Thus, both criteria should not be unconditionally applied to parthenogenetic and agamic species consisting of females alone. However, the absence of males also plays the role of a peculiar isolation mechanism which maintains the integrity of parthenogenetic species. Due to this, parthenogenetic forms of Lacerta saxicola Eversmann which can be easily distinguished in the morphological respect should be considered as independent agamic species: Lacertra armeniaca Meh., L. dahli Dar., L. rostombekovi Dar. and L. unisexualis Dar.

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Locus-specific PCR was used to study the genetic polymorphism in three populations of parthenogenetic lizard species Darevskia dahli. The analysis was carried at the two (GATA) n -containing loci (Du215 and Du281) using the sample of 26 individuals. A total of eight Du215 and three Du281 allelic variants were detected. It was demonstrated that all the lizards examined were heterozygous at these loci. In 12 animals, unusual Du215 allelic variant was revealed, the origin of which was thought to be associated with different types of genomic rearrangements, or segmental duplication. The populations studied were substantially different relative to the levels of allelic polymorphism, which could be explained by different habitation conditions, leading to accumulation of mutations in noncoding genome regions.

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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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Five new regional records of the rock lizards in Caucasus are described. The distribution of Darevskia alpina (Darevsky, 1967) on the northern slope of Mount Elbrus has been detailed: the species was found in the Emmanuel glade and in the gorge of the Kyzylkol River. The easternmost record of D. alpina is located in the upper stream of the Cherek Bezengi River in Kabardino-Balkaria. Darevskia caucasica vedenica (Darevsky et Roitberg, 1999) was first found on the territory of Dagestan in the area of the lake Kezenoyam and on the watershed of the Okholitlau and Khulhulau rivers. The existence of an isolated population of D. daghestanica (Darevsky, 1967) in the gorge of the Bolshaya Liakhvi River was confirmed, which is located in South Ossetia, on the southwestern border of the species range. When studying the collections of the Zoological Institute of the Russian Academy of Sciences, three specimens of D. dahli (Darevsky, 1957) were found from the village Alapars of the Kotayk region of Armenia collected in 1880. This locality is the southernmost and, moreover, the only record of the species in the Armenian volcanic highlands.

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The information is given on finding of males, having characters similar with Darevskia mixta (settled in 1968) and with D. armeniaca in the structure of the mixed experimental population of rocky lizards D. armeniaca and D.dahli. Data about distribution of the above mentioned species in the territory populated by them, characters of external morphology and others are cited. The possible reasons of not planned occurrence `D.dahli` in the population of D. armeniacа, including by hybridization are considered.

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Specimens of Dahl’s rocky lizard Darevskia dahli (Darevsky, 1957) was found among the introduced on the territory of Ukraine D. armeniaca (Mehely, 1909). The 11 specimens of Dahl’s rocky lizard was compared D. armeniaca from the same location by 16 external features and with 15 specimens of D. dahli from Georgia by 2 features. The results were commented.

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Data on biology of the partenogenetic rock lizards of Darevskia which are artificially acclimatized in Ukraine are provided. Biotopes and station of the mixed population of introduced species of D. armeniaca and D. dahli near the Denishi village in the Zhytomyr region are described. Expansion of an area of these species on inflows of the river Teteriv is noted. The new location of rocky lizards on the Bobrovka River near the Buki village is described. The seasonal and daily activity of lizards and density of their settlement in this region are investigated. The review of publications about population of introduced species of rocky lizards is provided. The factors limiting resettlement of parthenogenetic rocky lizards and promoting it are analyzed.

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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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Little mtDNA variation was observed among populations of the bisexual Caucasian rock lizard Lacerta mixta and unisexual L. dahli and L. armeniaca. Three haplotypes were detected in L. mixta and the maximum pairwise difference among the samples was 0.67%. No intra- and interspecific variation was found among populations of either L. armeniaca or L. dahli. Moreover, both unisexual species were identical to one of the three haplotypes of L. mixta. The limited variation in L. mixta is likely the result of bottleneck effect, although the small sample size may also be responsible. The lack of variation in the unisexuals was attributed to the restricted variation among the maternal parents, limited involvement of females in the hybridization, and recent origin.

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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 variability of mini-and microsatellite DNAs among the individuals of the parthenogenic Caucasian rock lizard, Lacerta dahli, from populations of Armenia was studied by multiloci DNA fingerprinting. The DNA fingerprints of all specimens of the parthenospecies appeared to be practically identical (species-specific), whereas those of the biparental species, L. raddei, proved to be individual-specific. Some of the mini-and microsatellite loci of parthenogenic animals revealed genetic heterogeneity. Quantitative estimates of the genetic variability of mini-and microsatellite DNA fragments, such as the mean index of similarity (S) and heterozygosity (H), for parthenogenic lizards were 0.967 and 0.025, respectively, whereas in bisexual species they were similar to those observed in other outbreeding populations (S = 0.38 and H = 0.695). Computer analysis of 1561 marker fragments of parthenogenic lizard DNAs discerned 12 DNA fingerprinting variants differing in 1-14 fragments. The data on the genetic variability of mini-and microsattelite loci of L. dahli may illustrate the process of spontaneous mutagenesis and the initial stage of intraspecies differentiation in natural populations of parthenogenic species.

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The molecular structure of the allelic variants of (AAT) n of the Du47D microsatellite locus was determined in parthenogenetic lizards Darevskia dahli, D. armeniaca, and D. rostombekovi. Comparative analysis of these alleles showed that they were characterized by perfect structure of microsatellite cluster, and were different in the number of (AAT) monomeric units, as well as in the combinations of species-specific substitutions and deletions in the microsatellite flanking regions. Molecular structure of microsatellite cluster, species-specific single nucleotide polymorphism (SNP), and different representation of alleles Du47 in the samples of parthenogenetic species examined point to the origin of the alleles from different bisexual species, which is consistent with the hybrid nature of unisexual species of the genus Darevskia. In addition, these data reflect different combination patterns of interspecific hybridization events with the participation of the same bisexual species upon the formation of hybrid genomes of parthenogenetic species. Possible application of the allelic variants of microsatellite loci of parthenogenetic lizards as the genetic markers for the analysis of the genomes of parthenogenetic species in the light of evolution, ecology, and parthenogenetic type of reproduction in vertebrates is discussed.

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An overview of the cases of introduction (both accidental and intentional) of amphibians and reptiles in the Caucasus and Crimea is provided. The introduction cases are systemized in accordance with the goals and ways of introduction and with regards to the expected scale of the impact and its nature. No negative consequences of the introduction of amphibian and reptile species in the Crimea and Caucasus are currently observed on any of the known examples. No cases of species naturalization, which the “invasion” term can be applied to, have been revealed. The importance of allochthonous populations as experimental sites to study microevolutionary processes and ecological adaptations of the species in new environmental conditions is discussed.

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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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Population and family samples of two morphological forms (mutant and normal with respect to dorsal color) of parthenogenetic lizard species Darevskia armeniaca were examined by means of DNA fingerprinting using M13 mini- and (GACA) n and (TCC) n microsatellite DNA markers. The morphological forms examined were characterized by clonally inherited, species-specific patterns of the DNA markers, which were different from the species-specific DNA fingerprints of the other parthenogenetic species of the genus Darevskia (D. dahli, D. unisexualis, and D. rostombekovi). The mean index of similarity (S) obtained for a sample of 36 individuals from three isolated populations using three types of DNA markers was 0.966. This was similar to those observed in D. dahli (0.962) (P > 0.05), but higher than that in D. unisexualis (0.950) (P < 0.05) and D. rostombekovi(0.875) (P < 0.01). Inheritance of M13 minisatellite and (TCC) n microsatellite DNA markers in the F1 offspring of parthenogenetic lizards was examined. It was shown that variability and clonal diversity of the fingerprint phenotypes observed in the populations and families of D. armeniaca could be at least partly explained by RFLP mutations in microsatellite repeats.

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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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Variation and clonal diversity in populations of the parthenogenetic rock lizard Darevskia rostombekovi was examined by means of multilocus DNA fingerprinting using mini- and microsatellite DNA markers M13, (GATA)4, and (TCC)50). The animals examined were shown to exhibit a clonally inherited, species-specific pattern of DNA markers (fingerprint profile) that is different from the species-specific patterns of parthenogenetic species D. dahli, D. armenica, and D. unisexualis. The mean intraspecific similarity indexS was 0.950 (0.003) for a sample of 19 animals from three isolated populations of North Armenia. This significantly differed from the estimate of this parameter for a sample of 21 animals including two individuals from mountainous, relict population from the vicinity of the Sevan Lake, which was equal to 0.875 (0.001). A comparison of DNA fingerprints showed differences between 21 individuals attaining 79 DNA fragments of 1801 mini- and microsatellite markers included in the analysis. The results obtained show that intraspecific variation in D. rostombekovi is higher than that in the previously studied parthenogenetic species D. dahli (S = 0.962) andD. unisexualis (S= 0.950) (P< 0.001). Taking into account that D. rostombekovi is considered monoclonal on the basis of allozyme data, the problem of clonal variability is discussed with regard to the evidence on nuclear DNA markers. It is suggested that the hybrid karyotype of D. rostombekovi, which is more unstable than that of D. dahli and D. unisexualis, generates a series of chromosomal rearrangements (mutations). This may lead to the appearance of a geographically isolated chromosomal race (clone) in the population inhabiting the southeastern coast of the Sevan Lake.

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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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Restriction enzymes were used to assay variation among mitochondrial DNAs from parthenogenetic and sexual species of Lacerta. This permitted identification of the sexual species that acted as the maternal parent of the various hybrid-parthenogenetic lineages. Lacerta mixta was the maternal parent for both L. dahli and L. armeniaca, L. valentini was the maternal parent for L. uzzelli, and L. raddei was the maternal parent of L. rostombekovi. The maternal ancestry of L. unisexualis is not as clear. The sample of L. nairensis was very similar to one from a population of L. raddei and either species could be the maternal parent of L. unisexualis. The parthenogenetic species all had very low nucleotide diversity in absolute terms and in comparison to their sexual relatives. The close similarity between mtDNAs from the parthenogenetic species and their respective sexual maternal ancestor species provides strong evidence for the recent origin of the parthenogens. The low diversity of the parthenogens indicates that few females were involved in their origins; the maternal parents of L. dahli and L. armeniaca could have come from a single population. The patterns of mtDNA variation in Lacerta are very similar to those in Cnemidophorus and Heteronotia, establishing recent and geographically restricted origins as a general feature of parthenogenetic lizards.

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Allozyme variation at 35 gene loci is investigated in 161 specimens of the uniparental Caucasian lizard Lacerta dahli from several locations in Armenia and Georgia. All individuals are heterozygotic at 12 loci, and homozygotic at 21 loci. Variation at two loci results in five uniparental clones. One clone is widespread whereas four are geographically restricted and are represented by only one or two individuals. Because successful formation of uniparental clones is rare, and because the biparental species forming them are now allopatric, the most probable explanation for the origin of the observed clonal diversity is either mutation or recombination within the common clone. The rare clones have lower levels of enzyme activity at four loci, suggesting that these organisms may be genetically deficient. Although the evidence points to change in a pre-existing clone, the possibility of multiple origins cannot be ruled out.

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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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The parthenogenetic species Darevskia rostombekowi is listed in the Red Book of Armenia and the IUCN Red List as ‘Endangered’. Among the noted threats to this species is competition with syntopic species. Therefore, our main goal was to compare the coexistence patterns among syntopic species. Census was conducted along five different transects (about 1 km long each) during May – September 2015, in two isolated populations. The numbers of counted parthenogenetic lizards of D. rostombekowi (40-46%, 23 individuals/ha) and D. unisexualis (60-54%, 35 individuals/ha) were not different between among (P= 0.87) in Sevan Lake population, but differed (P< 0.001) among the three parthenogenetic species [D. rostombekowi (30-34%, 6 individuals/ha), D. dahli (60-54%, 11 individuals/ha), and D. armeniaca (10-12%, 2 individuals/ha)] in the area of coexistence, in the vicinity of Dilijan city. Population density of D. rostombekowi from Sevan Lake was significantly higher (t-value = 6.50, P< 0.0001) than that in the Dilijan population. Herein, we analyze the temporal and spatial niches of lizards living synoptically to assess the degree of niche differentiation among them. No differences in vegetation density in the microhabitats used by syntopic species have been revealed for both populations. The comparison of daily activities have shown similar bimodal patterns for D. rostombekowi and D. dahli in Dilijan populations while in Sevan D. unisexualis shows a bimodal pattern of daily activity while D. rostombekowi a unimodal one. Moreover, it was noted that D. unisexualis appeared on the surface before D. rostombekowi in the morning and remained active longer. However, the number of D. rostombekowi individuals in May, just after hibernation, and in September, before hibernation, was higher than D. unisexualis. The lower density of D. rostombekowi in Dilijan population may have allowed synchronous activity cycles due to the lack of competition between species, in contrast to Sevan Lake populations.

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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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Methods of estimating within- and between-population gene diversity in parthenogenetic species using mini- and microsatellite DNA markers and modified Wright`s F ST statistic are presented with special reference to model populations of lizards of the genus Darevskia(D. dahli, D. armeniaca, D. unisexualis). We used DNA fingerprinting data for several populations of these species examined earlier. The effects of variation in M13 minisatellite, (GACA) n - and (TCC) n -microsatellite loci on the formation of within-population gene diversity in parthenogenetic species D. dahli and D. armeniaca were shown to be different. The equality of the realized gene diversity Hand its maximum possible value H max in two populations of D. dahli (H max = 0.032, H = 0.031, P 0.0431; H max = 0.024, H = 0.027, P = 0.09) and D. armeniaca (H max = 0.05, H = 0.053, P = 0.03; H max= 0.054, H = 0.055, P= 0.02) suggests that variation in (GACA) n loci substantially contributes to the maintenance of within-population genetic diversity. Analysis of between-population genetic diversity using loci M13, (GACA) n , and (TCC) n showed differentiation of D. dahli populations from northeastern and northwestern Armenia (F ST = 0.0272, P = 3 × 10–13) and genetic homogeneity of the Armenian and introduced to the Ukraine populations of D. armeniaca characteristic of one clone (F ST = 0, P = 1).

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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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The last species list of the European herpetofauna was published by Speybroeck, Beukema and Crochet (2010). In the meantime, ongoing research led to numerous taxonomic changes, including the discovery of new species-level lineages as well as reclassifications at genus level, requiring significant changes to this list. As of 2019, a new Taxonomic Committee was established as an official entity within the European Herpetological Society, Societas Europaea Herpetologica (SEH). Twelve members from nine European countries reviewed, discussed and voted on recent taxonomic research on a case-by-case basis. Accepted changes led to critical compilation of a new species list, which is hereby presented and discussed. According to our list, 301 species (95 amphibians, 15 chelonians, including six species of sea turtles, and 191 squamates) occur within our expanded geographical definition of Europe. The list includes 14 non-native species (three amphibians, one chelonian, and ten squamates).

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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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The parthenogenetic lizards Darevskia armeniaca and Darevskia dahli are widespread throughout the Lesser Caucasus, although they occupy different habitats. While these forms differ in size, colour and scalation, both D. armeniaca and D. dahli have a hybrid origin and a common maternal progenitor species. Current evidence about the patrilineal origin is inconclusive, and the exact number of ancestral lineages remains unknown. This study aimed to investigate the distribution of mitochondrial haplotypes and alleles at five microsatellite loci in both the parthenogenetic forms and their presumed ancestors, in order to infer the number of ancestral hybridization events. Mitochondrial DNA analysis confirmed that both forms descend matrilineally from D. mixta from a limited geographic area in Central Georgia. Simultaneously, the majority of both D. armeniaca and D. dahli shared the same genotypes at two microsatellite loci, but differed at the other three. This observation and overall study of the distribution of the microsatellite genotypes suggests that (1) both D. armeniaca and D. dahli descend from very few, possibly single original hybridization event, most likely D. mixta and D. portschinskii, hence the hypothesis of different paternal species for these two forms is rejected; (2) expansion of the original parthenogenetic hybrid form into the range of D. valentini, followed by backcrosses of D. valentini males with the parthenogens, triggered development of a new parthenogenetic form, D. armeniaca; (3) backcrosses and mutation are more likely reasons of genetic diversity both between and within the parthenogenetic forms than their multiclonal origin.

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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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Multilocus DNA fingerprinting has been used to study the variability of some mini- and microsatellite sequences in parthenogenetic species of Caucasian rock lizards of the genus Lacerta (L. dahli, L. armeniaca and L. unisexualis). We demonstrate that these clonally reproducing lizards possess species-specific DNA fingerprints with a low degree of intra- and interpopulation variation. Mean indices of similarity obtained using M13 DNA, (GACA)4 and (TCC)50 as probes were 0.962 and 0.966 in L. dahli and L. armeniaca, respectively. The mean index of similarity obtained using M 13 and GATA probes in L. unisexualis was estimated to be 0.95. However, despite the high degree of band-sharing, variable DNA fragments were revealed in all populations with the microsatellite probes. An particularly high level of variability was observed for (TCC)n microsatellites in populations of L. unisexualis. In fact TCC-derived DNA fingerprints were close to being individual-specific, with a mean index of similarity of 0.824. Fingerprint analysis of parthenogenetic families of L. armeniaca showed that all maternal fragments were inherited together by the progeny, and no differences in fingerprint patterns were observed. On the other hand, while identical DNA fingerprints were obtained from L. unisexualis families with M13 and (GATA)4 probes, use of the (TCC)50 probe revealed remarkable intrafamily variation in this species. It is assumed that the genetic heterogeneity observed in parthenogenetic populations may be explained, at least in part, by the existence of genetically unstable microsatellite loci. Our data serve to illustrate processes of spontaneous mutagenesis and the initial stages of clonal differentiation in natural populations of the lizard species studied.

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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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The all-female Caucasian rock lizard species Darevskia dahli and other parthenogenetic species of this genus reproduce normally via true parthenogenesis. Previously, the genetic diversity of this species was analyzed using allozymes, mitochondrial DNA, and DNA fingerprint markers. In the present study, variation at three microsatellite loci was studied in 111 specimens of D. dahli from five populations from Armenia, and new information regarding clonal diversity and clone formation in D. dahli was obtained that suggests a multiple hybridization origin. All individuals but one were heterozygous at the loci studied. Based on specific allele combinations, 11 genotypes were identified among the individuals studied. Individuals with the same genotypes formed distinct clonal lineages: one major clone was represented by 72 individuals, an intermediate clone was represented by 21 individuals, and nine other clones were rare and represented by one or several individuals. A new approach based on the detection and comparison of genotype-specific markers formed by combinations of parental-specific markers was developed and used to identify at least three hybridization founder events that resulted in the initial formation of one major and two rare clones. All other clones, including the intermediate and seven rare clones, probably arose through postformation microsatellite mutations of the major clone. This approach can be used to identify hybridization founder events and to study clone formation in other unisexual taxa.

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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.