David Tarkhnishvili - Academia.edu (original) (raw)

Papers by David Tarkhnishvili

Caucasiana

Visual inspection of several embryos of the parthenogenetic lizard Darevskia armeniaca revealed t... more Visual inspection of several embryos of the parthenogenetic lizard Darevskia armeniaca revealed the presence of an embryo with axial bifurcation (“two-headed”) on the stage of pigmented eyes and plate-like limb buds with a distinct border at the edges. This is the third recorded case of axial bifurcation in D. armeniaca, although two previous cases were mentioned without further discussion. Here the bicephalic embryo is described in detail and the potential reasons are discussed. The analysis of the literature on axial bifurcation in lacertids suggests that this type of developmental disorder may be particularly common in this parthenogenetic form. Hybridization may cause multiple developmental disorders, including incomplete separation of twin embryos; all parthenogenetic Darevskia have a hybrid origin, and this may cause the disorders rather than parthenogenetic reproduction by itself. The hypothesis needs further study with more representative samples of parthenogenetic and sexua...

Zoologischer Anzeiger, Mar 1, 2023

Here we report on collaborative expeditions run by ISU (Ilia State University, Tbilisi), ZFMK (Zo... more Here we report on collaborative expeditions run by ISU (Ilia State University, Tbilisi), ZFMK (Zoologisches Forschungsmuseum Alexander Koenig, Bonn) and external taxonomists in Georgia in 2018 and 2019 as part of the renewed close cooperation between Germany and Caucasus countries aiming at the exploration of biodiversity in the Caucasus region. The 2018 and 2019 field work campaigns serve as a starting point for a larger cooperative venture, planned to start in 2020-the Caucasus Barcode of Life Platform (CaBOL). To encourage participation by additional partners and to build an active expert network, we here describe the so-far collected material and collection methods, provide detailed information on collecting sites and the diversity of habitats and outline the goals of the planned CaBOL project. Building on experiences from the German Barcode of Life (GBOL) initiative, our goal is to increase expertise and capacity in the region for modern integrative taxonomy approaches.

Ecology and Evolution

To assess the genetic structure of Ponto‐Caspian brown trout (Salmo trutta complex) populations, ... more To assess the genetic structure of Ponto‐Caspian brown trout (Salmo trutta complex) populations, we analyzed both mitochondrial DNA sequences and genotypes at 10 microsatellite loci of fish caught in the Black Sea and from nine river catchments in Georgia, flowing into either the Black or Caspian seas. The results show that: (1) there is substantial genetic differentiation among Ponto‐Caspian trout populations, both among the populations of different nominal species and within those of the same species; (2) the genetic distance between conspecific populations from the Black and Caspian Sea basins exceeds that among the populations within the same basin. Moreover, within drainages, genetic distance correlates with the geographic distance; (3) the Black Sea itself is not a barrier to gene flow among the watersheds draining into the Black Sea; (4) some populations in the headwaters of the rivers draining into the Black Sea Basin fall out of this pattern and likely form a separate, non‐...

Zoology in the Middle East

Scientific Reports, 2021

This study clarifies the role of refugia and landscape permeability in the formation of the curre... more This study clarifies the role of refugia and landscape permeability in the formation of the current genetic structure of peoples of the Caucasus. We report novel genome-wide data for modern individuals from the Caucasus, and analyze them together with available Paleolithic and Mesolithic individuals from Eurasia and Africa in order (1) to link the current and ancient genetic structures via landscape permeability, and (2) thus to identify movement paths between the ancient refugial populations and the Caucasus. The ancient genetic ancestry is best explained by landscape permeability implying that human movement is impeded by terrain ruggedness, swamps, glaciers and desert. Major refugial source populations for the modern Caucasus are those of the Caucasus, Anatolia, the Balkans and Siberia. In Rugged areas new genetic signatures take a long time to form, but once they do so, they remain for a long time. These areas act as time capsules harboring genetic signatures of ancient source p...

PLOS ONE, 2020

We generated a phylogeny for Caucasian rock lizards (Darevskia), and included six other families ... more We generated a phylogeny for Caucasian rock lizards (Darevskia), and included six other families of true lizards (Lacertini), based on complete mitochondrial genome analysis. Nextgeneration sequencing (NGS) of genomic DNA was used to obtain 16 new mitogenomes of Darevskia. These, along with 35 sequences downloaded from GenBank: genera Darevskia, Zootoca, Podarcis, Phoenicolacerta, Takydromus, Lacerta, and Eremias-were used in the analysis. All four analytical methods (Bayesian Inference, BI; Maximum Likelihood, ML; Maximum Parsimony, MP; and Neighbor-Joining, NJ) showed almost congruent intrageneric topologies for Darevskia and other lizard genera. However, ML and NJ methods on one side, and BI and MP methods on the other harvested conflicting phylogenies. The ML/ NJ topology supports earlier published separation of Darevskia into three mitochondrial clades (Murphy, Fu, Macculloch, Darevsky, and Kupinova, 2000), but BI and MP topologies support that the basal branching occurred between D. parvula from the western Lesser Caucasus and the rest of Darevskia. All topologies altered the phylogenetic position of some individual species, including D. daghestanica, D. derjugini, and D. chlorogaster. Reanalysis after excluding four saturated genes from the data set, and excluding genus Eremias gives fully convergent topologies. The most basal branching for true lizards was between Far Eastern Takydromus and the Western Eurasian genera (BI). Comparing phylogenetic performance of individual genes relative to whole mitogenome data, concatenated 16S RNA (the least saturated gene in our analyses) and Cytochrome b genes generate a robust phylogeny that is fully congruent with that based on the complete mitogenome.

Three species of cetaceans, Phocoena phocoena, Delphinus delphis and Tursiops truncatus ponticus ... more Three species of cetaceans, Phocoena phocoena, Delphinus delphis and Tursiops truncatus ponticus are found in the Black Sea. The Black Sea populations of all three species show morpho-ecological peculiarities that leaded to their subspecific status: P. p. relicta (PPR), D. d. ponticus (DDP), and T. t. ponticus (TTP). It is not clear how long-lasting was their isolation from the core conspecific populations that ensured the development of adaptive features of PPR, DDP, and TTP. The analysis of mitochondrial haplotypes of PPR suggests that the split time of the at least maternal lineage of the Black Sea population of harbour porpoise lasted for over 100 ky (i.e. they should survive at least the latest glacial maximum within the Black Sea). However, the analysis of multiple microsatellite genotypes leaded some authors to suggest that the isolation is much less long, since middle Holocene. We re-analysed published mitochondrial sequences of all three Black Sea cetaceans along with sever...

Biological Journal of the Linnean Society, 2020

Phenotypic evolution can cause either divergent or convergent phenotypic patterns. Even adaptatio... more 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...

Amphibia-reptilia, Nov 2, 2022

Frontiers in Ecology and Evolution

Biological Journal of the Linnean Society

Caucasian rock lizards (Darevskia) are a speciose group with 42 described species from the Caucas... more Caucasian rock lizards (Darevskia) are a speciose group with 42 described species from the Caucasus Mountain region. We selected 11 species from Georgia and adjacent territories to explore whether their distribution depends on the distribution of congeneric taxa. We estimated two measures for each species pair: (1) niche overlap between all pairs of the studied species; (2) the extent of contact between the ranges of individual species. We then calculated the correlation between these measurements and the time of divergence between the species. The results showed that in sympatric and parapatric (but not allopatric) species, there is a highly significant correlation between the divergence time and the extent of the contact, as well as between the divergence time and the overlap of suitable habitats. The ranges of the evolutionarily closest species have the smallest extent of contact. Species separated later have overlapping ranges, although are separated by altitude. The most distan...

Biological Journal of the Linnean Society, 2022

We genotyped multiple populations of all seven parthenogenetic species of rock lizards, genus Dar... more 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 ...

microsatellite genotypes (number of nucleotides per STR allele) for 167 individual wolves and dog... more microsatellite genotypes (number of nucleotides per STR allele) for 167 individual wolves and dogs from Georgia (genotypes of wolves from the eastern and from the western Georgia shown separately). Microsoft Exel file, single spreadsheet

We studied the distribution of the mitochondrial DNA haplotypes and microsatellite genotypes at e... more We studied the distribution of the mitochondrial DNA haplotypes and microsatellite genotypes at eight loci in 102 grey wolves, 57 livestock guarding dogs, and 9 mongrel dogs from Georgia (Caucasus). Most of the studied dogs had mitochondrial haplotypes clustered with presumably East Asian dog lineages, and most of the studied wolves had the haplotypes clustered with European wolves, but 20% of wolves and 37% of dogs shared the same mitochondrial haplotypes. Bayesian inference with STRUCTURE software suggested that over 13% of the studied wolves had detectable dog ancestry and over 10% of the dogs had detectable wolf ancestry. 2-3% of the sampled wolves and dogs were identified, with a high probability, as first generation hybrids. These results were supported by the relatedness analysis which showed that 10% of wolves and 20% of dogs had closest relatives from an opposite group. The results of the study suggest that wolf-dog hybridization is a common event in the areas where large livestock guarding dogs are held in a traditional way, and that gene flow between dogs and grey wolves was an important force influencing gene pool of dogs for millennia since early domestication events. This process may have been terminated (1) in areas outside the natural range of grey wolves and (2) since very recent time, when humans started to more tightly control contacts of purebred dogs

Herpetological Journal, 2016

The rock lizards of the Darevskia saxicola complex are found exclusively in the west of the Great... more The rock lizards of the Darevskia saxicola complex are found exclusively in the west of the Greater Caucasus and in southern Crimea. The earliest split within this group occurred between D. saxicola from the northern and D. brauneri from the southern slopes of the Greater Caucasus, followed by the split between D. brauneri and the Crimean D. lindholmi, and the expansion of D. saxicola to the westernmost slopes of the Greater Caucasus. We collected nominal D. brauneri from the two easternmost populations of the species range: the valleys of the Tekhuri and Enguri rivers in Georgia. Analysis of mitochondrial DNA showed that the lizards from both valleys are deeply differentiated from each other and from previously characterised D. brauneri. Lizards from Tekhuri keep a basal position within the clade D. saxicola (excluding D. praticola), and lizards from Enguri are closer matrilineally to the northern Caucasian D. saxicola than to either of the populations of nominal D. brauneri. Tekhu...